Cnidaria is a phylum containing some 11,000 species of relatively simple invertebrate animals found exclusively in aquatic, mostly marine, environments. Cniderians include corals, sea anemones, jellyfish, sea pens, sea pansies, and sea wasps, and tiny freshwater hydra.
The name of the phylum comes from cnidocytes, which are specialized cells that carry stinging organelles. The names Coelenterata and Coelentera were formerly applied to the group, but as those names included the Ctenophores (comb jellies, phylum Ctenophora), they have been abandoned. Cnidarians are highly evident in the fossil records, having first appeared in the Precambrian era.
There are four main classes of Cnidaria:
Class Scyphozoa (true jellyfish)
Class Hydrozoa (Portuguese Man o' War, Obelia, Hydra, etc.)
Class Cubozoa (box jellies)
Class Anthozoa (anemones, corals, sea fans, etc.)
Theoretically, members of Cnidaria have life cycles that alternate between asexual polyps (the body as a vase shaped form), and sexual, free-swimming forms called medusae (singular medusa; the body in a bell-shaped form). The Anthozoa live only as polyps, while Scyphozoa live most of their life cycle as medusa. The Hydrozoa live as polyps, medusae, and species that alternate between the two. Invertebrates belonging to the class Cubozoa are named for their cube-shaped medusae, which form the dominant part of their life cycle. (New World Encyclopedia)
Jellyfish (Scyphozoa) are delicate, soft-bodied animals. They are invertebrates—jellyfish have no bones, exoskeleton, or shell to protect or support them. Instead, the water in which they live provides their body with the structural support it requires. If a jellyfish is removed from water or is washed ashore, it collapses and dies.
Jellyfish are cnidarians, a group of animals that also includes corals, hydras, and sea anemones. Cnidaria are all radially symmetrical. Their body parts are roughly symmetrical when viewed around a central axis. Jellyfish have no left or right side, when viewed side-on, they look approximately the same from every angle. (animals.about.com)
Cnidaria is a phylum containing over 10,000 species of animals found exclusively in aquatic (freshwater and marine) environments: they are predominantly marine species.
Their distinguishing feature is cnidocytes, specialized cells that they use mainly for capturing prey.
Their bodies consist of mesoglea, a non-living jelly-like substance, sandwiched between two layers of epithelium that are mostly one cell thick.
They have two basic body forms: swimming medusae and sessile polyps, both of which are radially symmetrical with mouths surrounded by tentacles that bear cnidocytes.
Both forms have a single orifice and body cavity that are used for digestion and respiration.
Many cnidarian species produce colonies that are single organisms composed of medusa-like or polyp-like zooids, or both (hence they are trimorphic). Cnidarians' activities are coordinated by a decentralized nerve net and simple receptors.
Several free-swimming species of Cubozoa and Scyphozoa possess balance-sensing statocysts, and some have simple eyes.
Not all cnidarians reproduce sexually, with many species having complex life cycles of asexual polyp stages and sexual medusae. Some, however, omit either the polyp or the medusa stage. (Wikipedia: Cnidaria)
Stinging cells called nematocyst found in cnidocyte cells.
Two body types polyp and medusa.
Cnidarians are classified into four main groups: swimming Scyphozoa (jellyfish); Cubozoa (box jellies); and Hydrozoa; and the almost wholly sessile Anthozoa (sea anemones, corals, sea pens). (Wikipedia: Scyphozoa)
The name Cnidaria comes from the Greek word "cnidos," which means stinging nettle. Casually touching many cnidarians will make it clear how they got their name when their nematocysts eject barbed threads tipped with poison.
There are four major groups of cnidarians:
Scyphozoa, the true jellyfish;
Hydrozoa, the most diverse group with siphonophores, hydroids, fire corals, and many medusae;
Cubozoa, the amazing box jellies with complex eyes and potent toxins; and
Anthozoa, which includes true corals, anemones, and sea pens. (ucmp.berkeley.edu)
The basic body shape of a cnidarian consists of a sac with a gastrovascular cavity, with a single opening that functions as both mouth and anus. It has radial symmetry, meaning that whichever way it is cut along its central axis (that is, by any plane that passes through its longitudinal axis), the resulting halves would always be mirror images of each other. (New World Encyclopedia: Anthozoa)
The body wall of all cnidarians is composed of two cell layers—the outer epidermis (or ectoderm) and the inner gastrodermis (or endoderm)—separated by a layer of gelatinous material known as mesoglea.
Marine invertebrates belonging to the Scyphozoan class of the Cnidaria phylum are usually referrred as true jellyfish. The term "jellyfish" is also frequently applied to certain other cnidarians (such as members of the class Hydrozoa and the class Cubozoa) that have a medusoid body form, Since jellyfish do not biologically qualify as actual "fish", the term "jellyfish" is considered a misnomer by some, who instead employ the names "jellies" or "sea jellies".
True Jellies (Scyphozoa)
Scyphozoan jellyfish can be divided into two types, those that are free-swimming medusae and those that are sessile (i.e., stem animals that are attached to seaweed and other objects by a stalk). The sessile polyplike forms constitute the order Stauromedusae. (Encyclopædia Britannica)
Jellyfish are marine invertebrates belonging to the Scyphozoan class of the Cnidaria phylum. The body of an adult jellyfish is composed of a bell-shaped, jellylike substance enclosing its internal structure, from which the creature's tentacles suspend.
Theoretically, members of Cnidaria have life cycles that alternate between asexual polyps (the body as a vase shaped form), and sexual, free-swimming forms called medusae (singular medusa; the body in a bell-shaped form). However, the Scyphozoa live most of their life cycle as medusa. The class name Scyphozoa means "cup animals," reflective of the dominant medusa form. The term comes from the Greek word skyphos, denoting a kind of drinking cup. Cnidaria, the name of the phylum, comes from cnidocytes, or nematocysts, which are specialized cells that carry stinging organelles. Each tentacle of a jellyfish is covered with these stinging cells, which can sting or kill other animals. Most jellyfish use them to secure prey or as a defense mechanism.
Most jellyfish are passive drifters that feed on small fish and zooplankton that become caught in their tentacles. The tentacles or oral arms are coated with thousands of microscopic nematocysts. Generally, each of these nematocysts has a "trigger" (cnidocil) paired with a capsule containing a coiled stinging filament, as well as barbs on the exterior. Upon contact, the filament will swiftly unwind, launch into the target, and inject toxins. It can then pull the victim into its mouth, if appropriate.
Although most jellyfish are not perniciously dangerous to humans, a few are highly toxic, such as Cyanea capillata. The recently discovered Carukia barnesi is also suspected of causing two deaths in Australia. (New World Encyclopedia)
The Scyphozoa, referred to as the true jellyfish (or "true jellies"), are an exclusively marine class of the phylum Cnidaria.
The class name Scyphozoa comes from the Greek word skyphos (σκύφος), denoting a kind of drinking cup and alluding to the cup shape of the organism. (Wikipedia: Scyphozoa)
Jellyfish or Jellies are the major non-polyp form of individuals of the phylum Cnidaria. They are typified as free-swimming marine animals consisting of a gelatinous umbrella-shaped bell and trailing tentacles. The bell can pulsate for locomotion, while stinging tentacles can be used to capture prey.
Jellyfish are found in every ocean, from the surface to the deep sea. Large, often colorful, jellyfish are common in coastal zones worldwide. Jellyfish have roamed the seas for at least 500 million years, and possibly 700 million years or more, making them the oldest multi-organ animal.
A medusa (plural: medusae) is a form of cnidarian in which the body is shaped like an umbrella, in contrast with polyps, which are approximately cylindrical in shape and elongated at the axis of the vase-shaped body. (Wikipedia: Jellyfish)
Most species of Scyphozoa have two life history phases, including the planktonic medusa or jellyfish form, which is most evident in the warm summer months, and an inconspicuous, but longer-lived, bottom-dwelling polyp, which seasonally gives rise to new medusae.
The fertilized egg produces a planular larva which, in most species, quickly attaches itself to the sea bottom. The larva develops into the hydroid stage of the lifecycle, a tiny sessile polyp called a scyphistoma. The scyphistoma reproduces asexually, producing similar polyps by budding, and then either transforming into a medusa, or budding several medusae off from its upper surface via a process called strobilation. The medusae are initially microscopic, and may take years to reach sexual maturity. (Wikipedia: Scyphozoa)
Jellyfish have tiny stinging cells in their tentacles to stun or paralyze their prey before they eat them. Inside their bell-shaped body is an opening that is its mouth. They eat and discard waste from this opening.
As jellyfish squirt water from their mouths they are propelled forward. Tentacles hang down from the smooth baglike body and sting their prey.
They dine on fish, shrimp, crabs and tiny plants. Sea turtles relish the taste of jellyfish. Some jellyfish are clear, but others are in vibrant colors such as pink, yellow, blue, and purple, and often are luminescent. The Chinese have fished jellyfish for 1,700 years. They are considered a delicacy and are used in Chinese medicine. (National Geographic Kids)
Jellyfish and Comb Jellies (Cnidaria & Ctenophora)
Jellyfish and comb jellies are gelatinous animals that drift through the ocean's water column around the world. They are both beautiful—the jellyfish with their pulsating bells and long, trailing tentacles, and the comb jellies with their paddling combs generating rainbow-like colors. Yet though they look similar in some ways, jellyfish and comb jellies are not very close relatives (being in different phyla—Cnidaria and Ctenophora, respectively) and have very different life histories. (Smithsonian Ocean Portal)
There is some concern that blooms of jellyfish—congregating of hundreds and even thousands of these animals—correlates with such anthropogenic impacts as overfishing and pollution.
Life cycle of scyphozoans
Life cycle of scyphozoans.
The developmental stages of scyphozoan jellyfish's life cycle: 1–3 Larva searches for site, 4–8 Polyp grows, 9–11 Polyp strobilates, and 12–14 Medusa grows.
1-8 – planula attachment and metamorphosis to scyphistoma stage; 9-10 – scyphistoma strobilation; 11 – ephyra release; 12-14 – transformation of the ephyra into an adult medusa.
Most jellyfish pass through two different body forms during their life cycle. The first is the polyp stage; in this phase, the jellyfish takes the form of either a sessile stalk that catches passing food, or a similar free-floating configuration. The polyp's mouth and tentacles are located anteriorly, facing upwards.
In the second stage, the jellyfish is known as a medusa. Medusae have a radially symmetric, umbrella-shaped body called a bell. The medusa's tentacles hang from the border of the bell. Jellyfish are dioecious; that is, they are either male or female. In most cases, to reproduce, a male releases his sperm into the surrounding water. The sperm then swims into the mouth of the female jelly, allowing the fertilization process of the ova to begin. Moon jellies, however, use a different process: their eggs become lodged in pits on the oral arms, which form a temporary brood chamber to accommodate fertilization.
After fertilization and initial growth, a larval form, called the planula, develops from the egg. The planula larva is small and covered with cilia. It develops into a polyp, which again, can be sessile or free-floating depending on the species. The polyp tends to be cup-shaped with tentacles surrounding a single orifice, perhaps resembling a tiny sea anemone.
The polyp may reproduce asexually by budding, the splitting off from the parent organism to form a new organism. In this case, the polyp is called a segmenting polyp, or a scyphistoma. The polyp grows to become a young, and then an adult, medusa.
Many jellyfish can bud off new medusae directly from the medusan stage.
Anatomy of a typical scyphozoan jellyfish, like Aurelia (Moon Jellyfish)
Left: A cutaway diagram of the moon jellyfish, Aurelia.
The true jellyfish, like Aurelia, are so-called because the bulk of their bodies
are composed of gelatinous or cartilaginous mesogloea (shown in blue in the above diagram). The medusae of the more familiar jellyfish are dome, saucer or bell-shaped with a
number of tentacles hanging down from the edge. The upper surface is the exumbrella, whilst the
undersurface is referred to as the subumbrella. The mouth hangs down from the subumbrella, on a
pendulous structure called the manubrium. The four corners of the mouth are typically drawn-out into
frilly oral arms.
Right: Subumbrella view of Aurelia, a scyphozoan jellyfish
Each of the 4 gonads occur in the stomach floor and hang down into
the subumbrella cavity. Many jellyfish have subumbrellar funnels, 4 deep pits or invaginations in the
subumbrella (which occur on the interradii) of unknown function, though water flows in and out of them as
the bell pulses (so they may be respiratory, excretory or chemo/thermosensory). In other jellyfish,
including Aurelia, the funnels disappear during the course of development to be replaced by shallower
depressions, called subgenital pits. These are visible in the diagram as a small circle in the subumbrella
inside each arc-shaped gonad.
The Classification of class scyphozoa
There are approximately 200 species of Scyphozoans organized into four orders.
The order Semaeostomeae contains some 50 species of mainly coastal-water jellyfish, several of which have very wide geographic ranges. Included among these are members of the genera Aurelia and Chrysaora and the big red jellyfish, Tiburonia granrojo (subfamily Tiburoniinae), one of only three species of jellyfish that lack tentacles.
The order Coronatae includes about 30 species of mostly deep-sea jellyfish, often maroon in colour. A deep circular groove delimits the central part of the bell-shaped body from the periphery, which is divided into broad flaps, or lappets. The marginal tentacles are large and solid. Some species are known to have a scyphistoma stage, but the life cycle of most of the forms has yet to be described. The coronate jellyfish are the most primitive of the present-day scyphozoans and are thought to be descended directly from the fossil form Conulata, which flourished between about 180 and 600 million years ago. Some of the known sessile stages form branched colonies, which were once separately identified under the name Stephanoscyphus.
The order Rhizostomeae includes some 80 described species. In these jellyfish the frilly projections (oral arms) that extend down from the underside of the body are fused, obliterating the mouth and forming a spongy area used in filter feeding. Marginal tentacles are lacking, and the gelatinous bell is firm and warty. In species whose life cycles are known, there is a typical benthic (bottom-dwelling) scyphistoma stage. Most members of the order are vigorous swimmers. Species of Cassiopea, the upside-down jellyfish, however, swim infrequently and sit inverted in tropical shallows, exposing their photosynthetic symbiotic algae to sunlight. The group Rhizostomeae is found mainly in shallow tropical to subtropical seas in the Indo-Pacific region, but members of the genus Rhizostoma, also called football jellyfish, often inhabit cooler waters, and Cotylorhiza is common in the Mediterranean.
The fourth order, Stauromedusae, comprises some 30 described species of nonswimming, stalked jellies. These species occur chiefly in cooler waters. They are goblet-shaped and fixed by a basal stalk; the mouth is situated at the upper end. Ranging from 1 to 10 cm (0.4 to 4 inches) in diameter, the body has a tetradiate design and typically bears eight clusters of tentacles. Some species can detach and resettle. Stauromedusae usually feed on small marine animals and live for several years. Development is direct from a larva into an adult. The polyp stage is suppressed. (Encyclopædia Britannica)
Differences between the classes of scyphozoa
Semaeostomeae - Flag-mouth jellyfishes have four long oral arms that drape down from their mouth.
Rhizostomeae - Members of this group lack tentacles. Have eigh oral arms which are fused, obliterating the mouth and forming a spongy area used in filter feeding. The gelatinous bell is firm and warty.
Coronatae - Crown jellyfishes have a groove that runs around their bell. The marginal tentacles are large and solid. They are deep-sea jellies which are rarely seen.
Stauromedusae - Sessile, stalked forms that lack free swimming medusa. The mouth is situated at the upper end. The body has a tetradiate design and typically bears eight clusters of tentacles.
Similarities and differences between the classes of scyphozoa
(Phylum: Cnidaria, Class: Scyphozoa, Order: Rhizostomae, Family: Mastigiidae, Genus: Phyllorhiza, Species:Phyllorhiza punctata) Phyllorhiza punctata is a species of jellyfish, also known as the floating bell, Australian spotted jellyfish or the white-spotted jellyfish. It is native to the West Pacific from Australia to Japan, but has been introduced widely elsewhere. It feeds primarily on zooplankton. Phyllorhiza punctata generally can reach up to 50 centimetres (20 in) in bell diameter, but in October 2007, one 72 cm (28 in) wide, perhaps the largest ever recorded, was found on Sunset Beach, North Carolina. (Wikipedia)
(Phylum: Cnidaria, Class: Scyphozoa, Order: Semaeostomeae, Family: Ulmaridae, Genus: Aurelia, Species: Aurelia aurita) Aurelia aurita (also called the moon jelly, moon jellyfish, common jellyfish, or saucer jelly) is a widely studied species of the genus Aurelia. The jellyfish is translucent, usually about 25–40 cm (10–16 in) in diameter, and can be recognized by its four horseshoe-shaped gonads, easily seen through the top of the bell. It feeds by collecting medusae, plankton, and mollusks with its tentacles, and bringing them into its body for digestion. It is capable of only limited motion, and drifts with the current, even when swimming. (Wikipedia)
(Phylum: Cnidaria, Class: Scyphozoa, Order: Rhizostomeae Family: Cepheidae, Genus: Cotylorhiza, Species: Cotylorhiza tuberculata) Cotylorhiza tuberculata is a species of jellyfish, also known as the Mediterranean jelly or fried egg jellyfish. It is commonly found in the Mediterranean Sea, Aegean Sea and Adriatic Sea. It can reach 35 cm in diameter. It seems that this jellyfish's sting has very little or no effect on humans. (Wikipedia)
(Phylum: Cnidaria, Class: Scyphozoa, Order: Rhizostomae, Family: Cepheidae, Genus: Cephea) Cephea is a genus of true jellyfish in the family Cepheidae. They are found in the Indo-Pacific and East Atlantic. They are sometimes called crown jellyfish, but this can cause confusion with the closely related genus Netrostoma or the distantly related species in the order Coronatae. (Wikipedia)
(Phylum: Cnidaria, Class: Scyphozoa, Order: Semaeostomeae, Family: Pelagiidae, Genus: Pelagia, Species: Pelagia noctiluca) Pelagia noctiluca is a jellyfish in the family Pelagiidae. In Latin, pelagia means "of the sea", nocti stands for night and luca means light; thus, Pelagia noctiluca can be described as a marine organism with the ability to glow in the dark.
This species of jellyfish, known in Europe as the mauve stinger amongst many other common names, is widely distributed in all warm and temperate waters of the world's oceans, including the Mediterranean Sea, Red Sea and Atlantic Ocean. It is also found in the Pacific Ocean, with sightings in warm waters off Hawaii, southern California and Mexico, as well as other Pacific locations. This is typically an offshore species, although sometimes it is washed near the coastlines and may be stranded in great numbers on beaches. The color varies worldwide, and in addition to pink or mauve, it is sometimes shades of golden yellow to tan. (Wikipedia)
(Phylum: Cnidaria, Class: Scyphozoa, Order: Semaeostomeae, Family: Pelagiidae, Genus: Chrysaora, Species: Chrysaora fuscescens) Chrysaora fuscescens (commonly known as the Pacific sea nettle or West Coast sea nettle) is a common free-floating scyphozoan that lives in the East Pacific Ocean from Canada to Mexico.
Sea nettles have a distinctive golden-brown bell with a reddish tint. The bell can grow to be larger than one meter (three feet) in diameter in the wild, though most are less than 50 cm across. The long, spiraling, white oral arms and the 24 undulating maroon tentacles may trail behind as far as 15 feet. For humans, its sting is often irritating, but rarely dangerous.
Chrysaora fuscescens has proven to be very popular for display at public aquariums due to their bright colors and relatively easy maintenance. It is possible to establish polyps and culture Chrysaora in captivity. When provided appropriate aquarium conditions, the medusae do well under captive conditions. (Wikipedia)
(Phylum: Cnidaria, Class: Scyphozoa, Order: Semaeostomeae, Family: Cyaneidae, Genus: Cyanea, Species: Cyanea capillata)
The lion's mane jellyfish (Cyanea capillata), also known as the giant jellyfish or the hair jelly, is the largest known species of jellyfish. Its range is confined to cold, boreal waters of the Arctic, northern Atlantic, and northern Pacific Oceans. It is common in the English channel, Irish Sea, North Sea and in western Scandinavian waters south to Kattegat and Øresund. It may also drift in to the south-western part of the Baltic Sea (where it cannot breed due to the low salinity). Similar jellyfish, which may be the same species, are known to inhabit seas near Australia and New Zealand. The largest recorded specimen found, washed up on the shore of Massachusetts Bay in 1870, had a bell with a diameter of 2.3 metres (7 ft 6 in) and tentacles 37.0 m (121.4 ft) long. Lion's mane jellyfish have been observed below 42°N latitude for some time in the larger bays of the east coast of the United States.
The lion's mane jellyfish uses its stinging tentacles to capture, pull in and eat prey such as fish, sea creatures and smaller jellyfish. (Wikipedia)
Lion's mane jellyfish (Image)
Lion's mane jellyfish (Cyanea capillata) and moon jellyfish (Aurelia aurita) in the Salish Sea between the Canadian province of British Columbia and the northwestern portion of the U.S. state of Washington.
(Phylum: Cnidaria, Class: Scyphozoa, Order: Rhizostomae, Family: Rhizostomatidae, Genus: Nemopilema, Species: Nemopilema nomurai) Nomura's Jellyfish (エチゼンクラゲ echizen kurage, Nemopilema nomurai) is a very large rhizostomae jellyfish, in the same size class as the lion's mane jellyfish, the largest cnidarian in the world. It is edible. (Wikipedia)
Hydrozoa (hydrozoans, from ancient Greek ὕδωρ, hydor, "water" and ζῷον, zoon, "animal") are a taxonomic class of individually very small, predatory animals, some solitary and some colonial, most living in salt water. The colonies of the colonial species can be large, and in some cases the specialized individual animals cannot survive outside the colony. A few genera within this class live in fresh water. Hydrozoans are related to jellyfish and corals and belong to the phylum Cnidaria.
Some examples of hydrozoans are the freshwater jelly (Craspedacusta sowerbyi), freshwater polyps (Hydra), Obelia, Portuguese man o' war (Physalia physalis), chondrophores (Porpitidae), "air fern" (Sertularia argentea), and pink-hearted hydroids (Tubularia).
Most hydrozoan species include both a polypoid and a medusoid stage in their lifecycles, although a number of them have only one or the other. For example, Hydra has no medusoid stage, while Liriope lacks the hydroid stage.
Perhaps the best-known hydrozoan, familiar to most students of introductory biology, is Hydra, pictured at left. Hydra never goes through a medusoid stage and spends its entire life as a polyp. However, Hydra is not typical of the Hydrozoa as a whole. Most hydrozoans alternate between a polyp and a medusa stage — they spend part of their lives as "jellyfish" which are hard to distinguish from scyphozoan jellyfish.
A great many hydrozoans are also colonial. Some form delicate branched colonies, while others, known as "fire corals," form massive colonies that resemble true corals. Other hydrozoans have developed pelagic (floating) colonies that are often confused with jellyfish, but unlike jellyfish they are composed of many individuals, all specialized for various functions. The "Portuguese man-o'war" and "by-the-wind-sailors" that often wash up on beaches are examples of these unusual colonial hydrozoans. (www.ucmp.berkeley.edu)
Note: The Obelia life cycle is similar to that of Scyphozoan jellyfish, the true jellyfish, The major difference is that a Scyphozoan jellyfish spends most of its life as a medusa, while Obelia spends most of its life as a polyp.
Reproduction in Hydrozoans
Most hydrozoans are colonial organisms whose polyps reproduce
asexually by forming small buds on the body wall. The
buds develop into polyps that eventually separate from the
colony and begin living independently. Many hydrozoans are
also capable of sexual reproduction. Some species of Hydra are
hermaphrodites, but in most species the sexes are separate.
The genus Obelia is typical of many marine colonial hydrozoans.
Obelia lives in colonies that form when one polyp asexually
produces buds that do not separate from it. Eventually,
there are numerous polyps attached to one stem, forming the
colony. The Obelia colony is branched like
deer antlers, with various polyps attached to the branched
stalks. The reproductive polyps give rise asexually to male and
female medusas. These medusas leave the polyps and grow to
maturity in the ocean waters.
During sexual reproduction, the medusas release sperm or
eggs into the water. The gametes fuse and produce zygotes that
develop into free-swimming, ciliated larvae called planulae. The planulae eventually settle on the ocean bottom
and develop into new polyps. Each polyp gives rise to a
new colony by asexual budding, and the life cycle is repeated.
Some colonial hydrozoans have both a medusa stage and a polyp stage in their life cycle. Each colony has a base, a stalk, and one or more polyps. Hydroid colonies are usually dioecious, which means that they have separate sexes—all the polyps in each colony are either male or female, but not usually both sexes in the same colony. Hydrozoan colonies are composed of a number of specialized polyps (or "zooids"), including feeding, reproductive, and sometimes, protective zooids. In some species, the reproductive polyps, known as gonozooids (or "gonotheca" in thecate hydrozoans) bud off asexually-produced medusae. These tiny, new medusae (which are either male or female) mature and spawn, releasing gametes freely into the sea in most cases. Zygotes become free-swimming planula larvae or actinula larvae that either settle on a suitable substrate (in the case of planulae), or swim and develop into another medusae or polyp directly (actinulae). Colonial hydrozoans include siphonophore colonies, Hydractinia, Obelia, and many others.
The medusa stage, if present, is the sexually-reproductive life cycle phase (that is, in hydrozoan species that have both polyp and medusa generations). Medusae of these species of Hydrozoa are known as "hydromedusae." Most hydromedusae have shorter life spans than the larger scyphozoan jellyfish. Some species of hydromedusae release gametes shortly after they are themselves released from the hydroids (as in the case of fire corals), living only a few hours, while other species of hydromedusae grow and feed in the plankton for months, spawning daily for many days before their supply of food or other water conditions deteriorate and cause their demise. (Source: New World Encyclopedia: Hydrozoa)
Cnidocytes and Nematocysts
Cnidaria, the name of the phylum, comes from cnidocytes, or nematocysts, which are specialized cells that carry stinging organelles. Each tentacle of a jellyfish is covered with these stinging cells, which can sting or kill other animals. Most jellyfish use them to secure prey or as a defense mechanism. (New World Encyclopedia: Jellyfish )
The tentacles of the man-of-war capture and immobilize prey like young fish, small shrimp, or tiny crustaceans called copepods.
The tentacles contain batteries of cells that house miniscule, hollow harpoons called nematocysts. Those barbed harpoons act like hypodermic needles, enabling the man-of-war to inject a potent mix of venom into a victim. (National Geographic)
The stinging, venom-filled nematocysts in the tentacles of the Portuguese man o' war can paralyze small fish and other prey.
Each tentacle bears stinging, venom-filled nematocysts (coiled, thread-like structures), which sting and kill adult or larval squids and fishes.
Turritopsis dohrnii (Immortal jellyfish)
Phylum: Cnidaria, Class: Hydrozoa, Order: Anthoathecata, Family: Oceaniidae, Genus: Turritopsis, Species: Turritopsis dohrnii) Turritopsis dohrnii, the immortal jellyfish, is a species of small, biologically immortal jellyfish found in the Mediterranean Sea and in the waters of Japan. It is one of the known cases of animals capable of reverting completely to a sexually immature, colonial stage after having reached sexual maturity as a solitary individual. Others include the jellyfish Laodicea undulata and Aurelia sp.1.
Like most other hydrozoans, T. dohrnii begin their life as free-swimming tiny larvae known as planula. As a planula settles down, it gives rise to a colony of polyps that are attached to the sea-floor. The polyps form into an extensively branched form, which is not commonly seen in most jellyfish. Jellyfish, also known as medusae, then bud off these polyps and continue their life in a free-swimming form, eventually becoming sexually mature. When sexually mature they have been known to prey on other jellyfish species at a rapid pace. All the polyps and jellyfish arising from a single planula are genetically identical clones. If a T. dohrnii jellyfish is exposed to environmental stress or physical assault, or is sick or old, it can revert to the polyp stage, forming a new polyp colony. It does this through the cell development process of transdifferentiation, which alters the differentiated state of the cells and transforms them into new types of cells.
Theoretically, this process can go on indefinitely, effectively rendering the jellyfish biologically immortal, although, in nature, most Turritopsis are likely to succumb to predation or disease in the medusa stage, without reverting to the polyp form.
The "immortal jellyfish" was formerly classified as Turritopsis nutricula.
Phylum: Cnidaria, Class: Hydrozoa, Order: Anthoathecata, Family: Oceaniidae, Genus: Turritopsis, Species: Turritopsis nutricula)
Turritopsis nutricula is a small jellyfish that once reaching adulthood, can transfer its cells back to childhood. It may do this process to live longer. Several different species of the genus Turritopsis were formerly classified as Turritopsis nutricula, including the "immortal jellyfish" which is now classified as Turritopsis dohrnii. (Wikipedia: Turritopsis nutricula)
(Phylum:Cnidaria, Class: Hydrozoa, Order:Limnomedusae, Family: Olindiidae, Genus: Olindias, Species: Olindias formosa)
The flower hat jelly (Olindias formosa) is a species of jellyfish occurring in the West Pacific off southern Japan. Characterized by lustrous tentacles that coil and adhere to its rim when not in use, the flower hat jelly's bell is translucent and pinstriped with opaque bands, making it easily recognizable. The flower hat jelly can grow to be about 15 cm (6 in) in diameter. It lives around 4–6 months. Its diet consists mostly of small fish, which are caught with the tentacles. Its sting is painful, but is not deadly to humans. It is powerful enough to leave a rash. (Wikipedia)
(Phylum: Cnidaria, Class: Hydrozoa, Order: Siphonophora, Family: Physaliidae, Genus: Physalia, Species: Physalia physalis) Portuguese man-of-war (genus Physalia), any of various jellylike marine animals of the order Siphonophora (class Hydrozoa, phylum Cnidaria) noted for their colonial bodies, floating habit, and powerful sting. The man-of-war is one of the best-known siphonophores. (Encyclopædia Britannica)
The Atlantic Portuguese man o' war (Physalia physalis), also known as the man-of-war, blue bottle, or floating terror, is a marine hydrozoan of the family Physaliidae found in the Atlantic Ocean, as well as the Indian and Pacific Oceans. Its venomous tentacles can deliver a painful (and sometimes fatal) sting. Despite its outward appearance, the Portuguese man o' war is not a jellyfish but a siphonophore, which is distinguished from jellyfish in that it is not a single multicellular organism, but a colonial organism made up of specialized minute individual organisms called zooids or polyps. These zooids are attached to one another and physiologically integrated to the extent that they cannot survive independently and function as if they were an individual organism. (Wikipedia)
Characteristics of Siphonophora: Colony of hydroids, floating structure, and powerful sting.
Physalia, the Portuguese Man-of-War (Portuguese
Man o' War or bluebottle), is found in all oceans, but prefers
the warmer waters of the Indian and Pacific oceans. It has a
remarkable float, usually bluish (sometimes violet) in colour
and typically up to 30 cm long or more. The float and its crest
or sail can be seen above the water with the long tentacles
trailing beneath the water's surface. Two species are actually
recognised, Physalis physalis or Portuguese Man o' War and
the smaller Physalis utriculus or Pacific Man o' War (though
probably both are commonly referred to as Portuguese Man
These creatures float on the waters, sailing by means of the
collapsible crest or sail (which seems very variable in size
judging from various photographs) dragging their fishing
tentacles through the water. The tentacles are armed with
stinging nematocysts and the venom of the larger species,
Physalia physalis, can be lethal to humans. The tentacles
typically reach up to 10 m to 30 m in length, though there are
reports of tentacles growing up to 50 m.
Siphonophores grow from single floating polyps which multiply asexually by budding, but with the progeny remaining physically and intimately
connected to one-another to form a single composite or colonial organism. In the Portuguese Man-of-War the float is a single individual, called
the pneumatophore, and each tentacle is an individual - the long fishing tentacles are called dactylozoids and function only to capture food
and defend the colony - being incapable of feeding themselves, as is the float. The tentacles hang down from half of the float, along with the
shorter feeding polyps called gastrozoids. Each gastrozoid has a mouth and a short tentacle and feeds the colony (some later lose their
mouth and develop into long dactylozoids). Also in the colony are short gonozoids which bear numerous spheroidal female gonophores and
male gonophores - the gonophores are the sexual 'organs' and are really modified medusae that remain attached to the colony and are
incapable of swimming. Odd gelatinous zooids may also be present, which resemble simple gelatinous projections.
What we see here is a division of labour - the pneumatophore gives the colony buoyancy, the dactyloxoids catch food and defend the colony
and the gastrozoids ingest food and the gonozoids function in reproduction.
(Phylum:Cnidaria, Class:Hydrozoa, Order:Anthomedusae, Family:Tubulariidae, Genus:Tubularia. Species: Tubularia-indivisa)
Tubularia indivisa, commonly known as the oaten pipes hydroid, is a species of large hydroid native to the northeastern Atlantic Ocean, the North Sea, Norwegian Sea, and the English Channel. The conical solitary polyps are found on dull yellow unbranched stems that reach 10 to 15 cm (3.9 to 5.9 in) in height with a diameter of 1.5 cm (0.59 in). They may be fused to a small number of other individual stems at their bases. The pinkish to red polyps resemble flowers, having two concentric rings of tentacles, with the outer rings being paler and longer than the inner ring. At the center is a pale pink gonotheca. They are preyed upon by nudibranchs.
(Phylum: Cnidaria, Subphylum: Medusozoa, Class: Hydrozoa, Subclass: Trachylinae, Order: Trachymedusae, Family: Rhopalonematidae, Genus: Crossota) Crossota is a genus of jellyfish of the family Rhopalonematidae. The genus comprises five species. Unlike most hydromedusae, these jellyfish do not have a sessile stage. Rather, they spend their entire lives in the water column as plankton. The genus Crossota is widespread throughout the oceans.
Watch the video at www.youtube.comWatch the video at National Oceanic and Atmospheric Administration site
NOAA Office of Ocean Exploration and Research, 2016 Deepwater Exploration of the Marianas.
This stunningly beautiful jelly was seen during Dive 4 of the 2016 Deepwater Exploration of the Marianas expedition on April 24, 2016, while exploring the informally named "Enigma Seamount" at a depth of ~3,700 meters.
Scientists identified this hydromedusa as belonging to the genus Crossota. Note the two sets of tentacles — short and long. At the beginning of the video, you'll see that the long tentacles are even and extended outward and the bell is motionless. This suggests an ambush predation mode. Within the bell, the radial canals in red are connecting points for what looks like the gonads in bright yellow.
Amazing Jellies: The mysteries of jellyfish and alien-like siphonophores (Video).
The green fluorescent protein (GFP) is a protein composed of 238 amino acid residues (26.9 kDa) that exhibits bright green fluorescence when exposed to light in the blue to ultraviolet range. Although many other marine organisms have similar green fluorescent proteins, GFP traditionally refers to the protein first isolated from the jellyfish Aequorea victoria. The GFP from A. victoria has a major excitation peak at a wavelength of 395 nm and a minor one at 475 nm. Its emission peak is at 509 nm, which is in the lower green portion of the visible spectrum. The fluorescence quantum yield (QY) of GFP is 0.79. The GFP from the sea pansy (Renilla reniformis) has a single major excitation peak at 498 nm. (Wikipedia)
Osamu Shimomura and Frank Johnson, working at the Friday Harbor Laboratories of the University of Washington in 1961, first isolated a calcium-dependent bioluminescent protein from the Aequorea victoria jellyfish, which they named aequorin. During the isolation procedure, a second protein was observed that lacked the blue-emitting bioluminescent properties of aequorin, but was able to produce green fluorescence when illuminated with ultraviolet light. Due to this property, the protein was eventually christened with the unceremonious name of green fluorescent protein (GFP). (www.microscopyu.com)
Aequorea victoria (Phylum:Cnidaria, Subphylum: Medusozoa, Class:Hydrozoa, Subclass:Leptolinae, Order:Leptomedusae, Suborder: Conica, Family: Aequoreidae, Genus: Aequorea, Species: A. victoria), also sometimes called the crystal jelly, is a bioluminescent hydrozoan jellyfish, or hydromedusa, that is found off the west coast of North America.
The species is best known as the source of two proteins involved in bioluminescence (aequorin) and fluorescence (green fluorescent protein). Their discoverers, Osamu Shimomura and colleagues, won the 2008 Nobel Prize in Chemistry for their work.
Almost entirely transparent and colorless, and sometimes difficult to resolve, Aequorea victoria possess a highly contractile mouth and manubrium at the center of up to 100 radial canals that extend to the bell margin. The bell margin is surrounded by uneven tentacles, up to 150 of them in fully-grown specimens. (Wikipedia)
Left: Fluorescent Jellyfishes
Amazing fluorescent jellyfish shot in an aquarium of Rhenen's zoo in The Netherlands.
Right: Fluorescent Jellyfish
Green fluorescent protein is a protein extracted from jellyfish, which fluoresces green when placed under blue light.
The crystal jellyfish (Aequorea victoria) has about three hundred photoctyes located on the edge of its umbrella, when stimulated they give off green light.
Aequorea victoria photocytes are located on the edge of the umbrella. The left image shows a microscopic view of some photocytes. The central photograph shows the bioluminescence of the photocytes, while the right hand image shows the jellyfish under visible light. The blue in the photograph on the right is not due to bioluminescence or fluorescence, it is due to visible light reflection. The bioluminescence as seen in the central photograph appears only when the jellfish is touched or disturbed.
Atolla wyvillei (Phylum: Cnidaria, Class: Scyphozoa, Order: Coronatae, Family: Atollidae, Genus: Atolla), also known as Atolla jellyfish or Coronate medusa, is a species of deep-sea crown jellyfish (Scyphozoa: Coronatae). It lives in oceans around the world. Like many species of mid-water animals, it is deep red in color. This species was named in honor of Sir Charles Wyville Thomson, chief scientist on the Challenger expedition.
It typically has 20 marginal tentacles and one hypertrophied tentacle which is larger than the rest. This long trailing tentacle is thought to facilitate prey capture.
This species is bioluminescent. When attacked, it will launch a series of flashes, whose function is to draw predators who will be more interested in the attacker than itself. This has earned the animal the nickname "alarm jellyfish". (Wikipedia)
(Phylum: Cnidaria, Subphylum: Medusozoa, Class: Hydrozoa, Subclass: Leptolinae, Order: Anthomedusae, Suborder: Capitata, Family: Hydridae, Genus: Hydra) Hydra is a genus of small, fresh-water animals of the phylum Cnidaria and class Hydrozoa, native to the temperate and tropical regions. Biologists are especially interested in Hydra because of their regenerative ability – they appear not to age or die of old age. (Wikipedia)
Left: Hydra Body Forms
Right: Hydra model
(1. Epidermis 2. Gastrodermis 3. Mesoglea 4. Basal disc (foot) 5. Tentacles 6. Discharged nematocysts 7. Gastrovascular cavity 8. Bud 9. Ovary with egg 10. Testis.)
Hydra can move by tumbling
The abundant freshwater genus Hydra is
unique among hydrozoans because it
has no medusa stage and exists only as a
solitary polyp. Hydras live in quiet
ponds, lakes, and streams. They attach
to rocks or water plants by means of a
sticky secretion they produce in an area
of their body called the basal disk.
Hydras can glide around by decreasing
the stickiness of the material secreted by
their basal disk. Sometimes hydras move
by tumbling, as shown in Figure 8. To
tumble, the hydra bends its body over
and touches the surface it is attached to
with its tentacles. Then it pulls its basal
disk free, flipping it over to the other
side of its tentacles. The basal disk then
reattaches, and the hydra returns to an
upright position. Most hydras are brown
or white, like the one in Figure 8. Others
appear green because of the algae living
within their cells.
Box jellyfish (class Cubozoa) are cnidarian invertebrates distinguished by their cube-shaped medusae. Some species of box jellyfish produce extremely potent venom: Chironex fleckeri, Carukia barnesi and Malo kingi. Stings from these and a few other species in the class are extremely painful and can be fatal to humans. (Wikipedia: Box jellyfish)
The class Cubozoa contains two orders, Carybdeida and Chirodropida. Together, both orders comprise about 20 described species. Although some reach a diameter of 25 cm (10 inches), most range between 2 to 4 cm (1 to 2 inches). The jelly is rather spherical but squared off along the edges, giving rise to the common name of box jellies. The genera Chironex and Chiropsalmus, commonly called sea wasps, occur widely from Queensland northward to about Malaya. These forms have remarkably sophisticated eyes, and they are dangerously venomous; a moderate sting can cause death within a few minutes. In all the box jellies so far studied, the polyp stage produces but a single medusa. Through the process of budding, polyps emerge from a medusa or from another polyp. Essentially, a single planula larva may produce numerous, genetically identical medusae. (Encyclopædia Britannica)
Characteristics of Cubozoa
Cubozoans, or box jellies, as their
name implies, have a cube-shaped medusa. Their polyp
stage is inconspicuous, and in some species, it has never been
observed. Most box jellies are only a few centimeters in height,
although some are 25 cm (10 in.) tall. A tentacle or group of tentacles
is found at each corner of the “box.” Stings of some species,
such as the sea wasp, can inflict severe pain and even death among
humans. The sea wasp lives in the ocean along the tropical northern
coast of Australia. (shapeoflife.org)
Box Jellyfish The tentacles of a box jellyfish (Chironex fleckeri) trail behind it and can reach 15 feet (4.6 meters) in length. Found in northern Australia and adjacent waters, a sting from this species can be deadly. This species of box jellyfish, the largest, can have as many as 60 tentacles.
(Phylum: Cnidaria, Class: Cubozoa, Order: Carybdeida, Family: Tripedaliidae, Genus: Tripedalia, Species: Tripedalia cystophora)
Tripedalia cystophora is a small species of box jellyfish in the family Tripedaliidae. It is native to the Caribbean Sea and the Central Indo-Pacific.
Tripedalia cystophora is a small box jellyfish belonging to the family of Tripedaliidae. It is found in the Caribbean Sea and the Indian and Pacific Oceans Center. This is a fast swimmer, and she has twenty-four eyes in its rhopalies.
Cubozoan visual system in Tripedalia cystophora
Cubozoan visual system in Tripedalia cystophora Cubozoan visual system: The visual system of the cubozoan Tripedalia cystophora (A) comprises four sensory structures called rhopalia (B). Each rhopalium carries six eyes of four morphological types (lower lens eye LLE, upper lens eye ULE, pit eye PE and slit eye SE) and a light sensitive neuropil (NP, red broken line). The eyes are responsible for the image formation in the animal and the light sensitive neuropil is thought to be involved in diurnal activity.
(Phylum: Cnidaria, Class: Cubozoa, Order: Chirodropida, Family: Chirodropidae, Genus: Chironex, Species: Chironex fleckeri) Chironex fleckeri, commonly known as sea wasp, is a species of deadly venomous box jellyfish found in coastal waters from northern Australia and New Guinea north to the Philippines and Vietnam. It has been described as "the most lethal jellyfish in the world", with at least 63 known deaths in Australia from 1884 to 1996.
Notorious for its sting, C. fleckeri has tentacles up to 3 m (9.8 ft) long covered with millions of cnidocytes which, on contact, release microscopic darts delivering an extremely powerful venom. Being stung commonly results in excruciating pain, and if the sting area is significant, an untreated victim may die in two to five minutes. The amount of venom in one animal is said to be enough to kill 60 adult humans (although most stings are mild). (Wikipedia)
Chirodropida is an order of box jellyfishes. They can be distinguished from other box jellyfish by the presence of branched muscular bases at the corners of their cubic umbrella, and of small saccules associated with the gastric cavity. They typically have multiple tentacles at each corner. (Wikipedia: Chirodropida)
(Phylum: Cnidaria, Class: Cubozoa, Order: Chirodropida, Family: Chirodropidae, Genus: Chironex, Species: Chironex yamaguchii) Chironex yamaguchii, commonly known as habu-kurage in Japanese, is a species of box jellyfish found in coastal waters around Japan, on Okinawa and the Ryukyu Islands, and in the Philippines. It is highly venomous.
In the past, the box jellyfish found in Japan and known locally as habu-kurage, has been considered to be identical to Chiropsalmus quadrigatus found in Malaysia. It has now been established that it is a different species and is more closely related to Chironex fleckeri, however, the name Chiropsalmus quadrigatus is widely used in the literature.
Anthozoa is a class within the phylum Cnidaria. Unlike other cnidarians, anthozoans do not have a medusa stage in their development. Instead, they release sperm and eggs that form a planula, which attaches to some substrate on which the cnidarian grows. Some anthozoans can also reproduce asexually through budding. More than 6,100 species have been described.
The name comes from the Greek words άνθος (ánthos; "flower") and ζώα (zóa; "animals"), hence ανθόζωα (anthozoa) = "flower animals", a reference to the floral appearance of their perennial polyp stage.
Like those of other cnidarians, the individual polyps have a cylindrical body crowned by a ring of tentacles surrounding the mouth. The mouth leads into a tubular pharynx which descends for some distance into the body before opening into the gastrovascular cavity that fills the interior of the body and tentacles. Unlike other cnidarians, however, the cavity is subdivided by a number of radiating partitions, or mesenteries. The gonads are also located within the cavity walls.
All cnidarian species can feed by catching prey with nematocysts; sea anemones are capable of catching fish and corals of catching plankton. Some of the species also harbour a type of algae, dinoflagellates called zooxanthellae, in a symbiotic relationship; the reef building corals known as hermatypic corals rely on this symbiotic relationship particularly. The zooxanthellae benefit by using nitrogenous waste and carbon dioxide produced by the host while the cnidarian gains photosynthetic capability and increased calcium carbonate production in hermatypic corals.
Anemones live in isolation. However, most corals form colonies of genetically identical polyps. These closely resemble anemones in structure, although they are generally much smaller. Stony coral are found in most seas. (Wikipedia)
Anthozoa is a class of marine invertebrates within the phylum Cnidaria that are unique among cnidarians in that they do not do not have a medusa stage in their development. These exclusively polypoid cnidarians are characterized by a tubular body with tentacles around the mouth and most are sedentary after the larval stage. Anthozoa includes the sea anemones, corals, sea pens, sea pansies, and sea fans, among others.
Anthozoa is the largest of the four classes of Cnidaria with over 6,000 species. They are found worldwide in all oceans, from the Arctic to the Antarctic. Anthozoa means "flower animals," which is descriptive of this class of invertebrates.
Anthozoans provide a number of values for human beings. Coral reefs are major tourist attractions and also provide a habitat for fish, mollusks, urchins, and crustaceans that serve as food for people. Anthozoans are used in the aquarium trade, to make coral jewelry, and scleractinian skeletons are even used as building materials and in bone grafts. Despite these values, various human activities (fishing, development, marine pollution) have had negative effects on coral reefs, with more than half of the world's coral reefs considered to be threatened.
Anthozoans are essentially a tubular sac, with a mouth and tentacles position around the mouth on a flattened upper surface known as an oral disk. As with other cnidarians, the tentacles surrounding the mouth have stinging cells and the mouth is the only entry to the digestive system. (New World Encyclopedia)
The Class Anthozoa includes a variety of animals that have polyps with a flower-like appearance. In these forms, the gastrovascular cavity is large. It is divided by walls or septa, which arise as folds from the body wall. These folds, along with the mouth and pharynx, are usually arranged in a biradially symmetric pattern. (The Animal Diversity Web)
Characteristics of Anthozoans
Anthozoans are exclusively polypoid cnidarians and do not have a medusa stage in their development. Instead, they release sperm and eggs that form a planula, which attaches to some substrate on which the organism grows. Some anthozoans can also reproduce asexually through budding.
The polyp has a tubular, cylindrical body with radial symmetry. As in all cnidarians, the body wall is composed of two cell layers—the outer ectodermis (or epidermis) and the inner gastrodermis—separated by a layer of gelatinous material known as mesoglea. The hallow entacles bearing stinging cells surround the mouth, which is the only opening to the closed digestive system (the coelenteron or gastrovascular cavity).
The mouth leads to a pharynx, a short tube leading to the coelenteron. The pharynx typically has one or more ciliated grooves (siphonoglyphs) that funnel water into the coelenteron. Characteristically, the order Actiniaria has two siphonoglyphs, the order Zoantharia has one, and order Corallimorpharia has weak siphonoglyphs or simply absent.
The closed digestive cavity (the coelenteron or gastrovascular cavity) is subdivided by infoldings of the gut wall into chambers (the mesenteries) separated by vertical septae.
The tentacles, the septae, and the mesenteries display either six-fold or eight-fold symmetry, and this feature is used to subclassify the class Anthozoa into Hexacorallia (6-fold symmetry) and Octocorallia (8-fold symmetry). Cerianthids have two circlets of tentacles, one around the mouth and the other around the edge of the oral disc.
A unique characteristic of cnidarians is the cnida, a complex intracellular capsule containing an eversible hollow tubule that can be released to sting or trap prey. Eversible means that the structure can turn inside out. There are three basic types of cnidae, and all can be found in the class Anthozoa. Nematocysts, which contain toxins and are typically armed with spines for penetrating the tissues of other organisms, are possessed by all anthozoans. Spirocysts are sticky rather than penetrating and are found only in the hexacorallians. Ptychocysts are unique to the cerianthid tube-dwelling anemones and are used to construct their tubes.
Nematocysts, which contain toxins and are typically armed with spines for penetrating the tissues of other organisms, are possessed by all anthozoans. Spirocysts are sticky rather than penetrating and are found only in the hexacorallians. Ptychocysts are unique to the cerianthid tube anemones and are used to construct their tubes.
Species in the orders Scleractinia, Antipatharia and Subclass Octocorallia produce skeletons. In the Scleractinia, the living tissue essentially lies above an external skeleton made of calcium carbonate secreted by the ectodermis.
Antipatharians secrete an internal horny skeleton that is flexible, black in color, and equipped with thorns on its surface. Antipatharian skeletons are usually branching treelike
Octocorals secrete an internal skeleton composed of a protein called gorgonin, calcium carbonate, or a combination of both. Octocorallian skeletons are usually branching treelike or whiplike forms.
Helioporaceans produce a massive skeleton that is blue in color and resembles those found in the stony corals.
Octocorals also secrete small calcareous sclerites (hardened plates) of a variety of shapes and colors that are embedded in the mesenchyme and that may give a spiny or scaly appearance to the colony.
Soft corals of order Alcyonacea lack a supporting internal skeleton and can inflate or deflate the fleshy colony by funneling water into or out of their polyps.
With the exception of the zoanthid genus Gerardia, species in the remaining anthozoan orders do not secrete a skeleton.
A few actiniarians secrete a chitinous tube, and one genus is able to form a chitinous coiled shell, similar in shape to a snail shell, that is inhabited by a hermit crab.
Cerianthids build soft, felt-like tubes from fired ptychocysts.
Anthozoans may be either solitary or colonial. In colonial species, the polyps are united by living tissue, the coenenchyme, and their gastrovascular cavities are joined by canals or tubes.
Actiniarians and ceriantharians are exclusively solitary, and the octocorals and antipatharians are exclusively colonial, but the remaining orders have both types of morphologies.
Solitary polyps are commonly 0.5–2 in (1–5 cm) in diameter at the oral disk, but the largest species grow to 3 ft (1 m) across.
Polyps of colonial species are typically much smaller (<0.4 in (5 mm)), but the colonies themselves can be quite large. Octocorallian and antipatharian colonies may grow >8 ft (2.5 m) tall, and some scleractinian corals may reach a size of 19.5 ft (6 m) in height and width.
Colonial anthozoans may reach a great age. For example, many octocorals are 100 or more years old, and the deep-sea zoanthid Gerardia has been estimated to be 1800 years old.
Anthozoa is the largest class in the phylum Cnidaria, with over 6,000 extant species divided among nine orders and classified in two subclasses. The nine orders are as follows:
Subclass Hexacorallia --- characteristic six-fold symmetry (Anthozoans with six-branched tentacles and six septae in their polyp structure).
Order Actiniaria, the sea anemones; 42 families
Order Ceriantharia, the tube anemones; three families
Order Scleractinia, the true (stony or hard) corals; 25 families
Order Antipatharia, the black (thorny) corals and wire corals; five families
Order Corallimorpharia, the mushroom (false) corals (also known as mushroom anemones or disc anemones); 4 families
Order Zoantharia (= Zoanthidea), the zoanthids; four families
Subclass Octocorallia --- characteristic eight-fold symmetry (Anthozoans with eight-branched tentacles and eight septae in their polyp structure).
Order Helioporacea, the blue corals; two families
Order Alcyonacea, the soft corals, gorgonians (sea fans, and sea whips); 29 families
Order Pennatulacea, the sea pens and sea pansies; 16 families
Some authors classify the Ceriantharia and Antipatharia together in a third subclass, the Ceriantipatharia, but genetic evidence does not support this grouping.
Anthozoa is divided into three subclasses, Hexacorallia, Octocorallia, and Ceriantharia. The Hexacorallia include the stony corals, the sea anemones and the zoanthids. These groups have polyps that generally have 6-fold symmetry. The Octocorallia include blue coral, soft corals, sea pens, and gorgonians (sea fans and sea whips). These groups have polyps with 8-fold symmetry, each polyp having eight tentacles and eight mesenteries. Ceriantharia are the tube-dwelling anemones.
Octocorals have eight pinnate (parts arranged on each side of a common axis) tentacles and eight septa; hexacorals have septa and tentacles—usually simple—in multiples of six. Cerianthids have two circlets of tentacles, one around the mouth and the other around the edge of the oral disc. There are a number of other details of polyp anatomy that are used to distinguish the orders of Anthozoa.
-Coral and Sea Anemones.
-Eat mostly small plankton.
-no medusa stage, planular instead.
-some have zooxanthellae (symbiotic association).
-can live as individuals or in colonies.
-Corals provide protection and food source for many organisms. Reefs.
-Tropical marine habitat.
-Mouth surrounded by tentacles with nematocysts.
-Secretes nonliving substance around outside of body to support and protect soft body tissues.
-Reproduces sexually by producing a free-swimming larva (planula) or asexually by budding or fission.
-Cylindrical, with radial symmetry.
Subclass Hexacorallia --- Characteristic six-fold symmetry
Order Actiniaria (the sea anemones) -- With 2 gullet groves (Sphonoglyphs)
Order Ceriantharia (the tube anemones) -- With anal pore
Order Scleractinia (the stony corals) -- With calcareous skeleton
Order Antipatharia (the black corals) -- With horny, thorny skeleton
Order Corallimorpharia (the mushroom corals/mushroom anemones)) -- Gullet groves weak or absent
Order Zoantharia (the zoanthids) -- With 1 gullet grove (Sphonoglyph)
Subclass Octocorallia --- Characteristic eight-fold symmetry
Order Helioporacea (the blue corals) -- Colonial, solid skeleton of non-spicular aragonite
(Soft corals) -- Colonial, fleshy body of spicular-calcite skeleton.
(Gorgonians: sea fans and sea whips) -- Colonial, branching skeleton, spicules in flesh
Order Pennatulacea, (the sea pens and sea pansies) -- Colonial, un-branching axis, spicules in flesh
Sea anemones are a group of water-dwelling, predatory animals of the order Actiniaria. They are named for the anemone, a terrestrial flower. Sea anemones are classified in the phylum Cnidaria, class Anthozoa, subclass Hexacorallia, order Actiniaria. They often have large polyps that allow for digestion of larger prey and they also lack a medusa stage.
Anemones tend to stay in the same spot until conditions become unsuitable, or a predator attacks them. In that case, anemones can release themselves from the substrate and use flexing motions to swim to a new location. Most sea anemones attach temporarily to submerged objects; a few thrust themselves into the sand or live in burrows; a few are parasitic on other marine organisms, and some have symbiotic relationships with hermit crabs. (Wikipedia)
Sea anemones are flower-like, filter feeding, marine invertebrates of the order Actinaria of the phylum Cnidaria. Named after a terrestrial flower (the anemone), these aquatic animals are classified with the corals in the Class Anthozoa, which means "flower animals." However, they lack the external or internal calcareous skeletons of the corals.
Anemones range in size from less than 1¼ centimeters (½ inch) to nearly two meters (six feet) in diameter.
A sea anemone is basically the typical polyp: a small sac, attached to the bottom by an adhesive foot, with a column shaped body ending in an oral disc. The mouth is in the middle of the oral disc, surrounded by tentacles. Anemones have a range of ten tentacles to hundreds.
The order of sea anemones, Actiniaria, are typically classified into four suborders: Suborder Endocoelantheae, Suborder Nyantheae, Suborder Protantheae, and Suborder Ptychodacteae. (New World Encyclopedia)
They have extremely pliable bodies that can undergo drastic, though slow, shape changes, thanks to the thick mesoglea (gel) within their body wall. The properties of the mesoglea allow sea anemones to resist sudden forces, like a strong ocean current, but to adapt their shape deliberately if needed to open for feeding or to become compact for protection. (EOL)
Sea anemones are essentially tubelike animals. One end of an anemone’s body is attached to or dug into the seafloor, while the other hosts a mouth surrounded by tentacles.
Tube-dwelling anemones or ceriantharians look very similar to sea anemones, but belong to an entirely different order of anthozoans. They are solitary, living buried in soft sediments. Tube anemones live and can withdraw into tubes, which are composed of a fibrous material made from secreted mucus and threads of nematocyst-like organelles known as ptychocysts.
Anatomy of a polyp of Sea anemones
Sea anemones are solitary polyps 5-100 mm in height and 5-200 mm in diameter or larger. They are often brightly colored and look like flowers on the seafloor. The anemone's thick, heavy body rests on a pedal disk and supports an upward-turned mouth surrounded by hollow tentacles. Sea anemones feed on various invertebrates and fish. They attach to a variety of substrates, or may be mutualistic with hermit crabs, living attached to crab's shell.
A sea anemone is a sessile polyp attached at the bottom to the surface beneath it by an adhesive foot, called a basal disc, with a column-shaped body ending in an oral disc. Most are from 1.8 to 3 cm (0.71 to 1.18 in) in diameter, but anemones as small as 4 mm (0.16 in) or as large as nearly 2 m (6.6 ft) are known. They can have from a few tens to a few hundred tentacles.
The mouth, also the anus of the sea anemone, is in the middle of the oral disc surrounded by tentacles armed with many cnidocytes, cells that are both defensive and used to capture prey. The mouth is typically slit-like in shape, and bears a groove at one or both ends. The groove, termed a siphonophore, is ciliated, and helps to circulate water through the gastrovascular cavity.
The mouth opens into a flattened pharynx. This consists of an in-folding of the body wall, and is therefore lined by the animal's epidermis. The pharynx typically runs for about two-thirds the length of the body before opening into the gastrovascular cavity that fills the remainder of the body.
The gastrovascular cavity itself is divided into a number of chambers by mesenteries radiating inwards from the body wall. Some of the mesenteries form complete partitions with a free edge at the base of the pharynx, where they connect, but others reach only partway across. They have stomach lining on both sides, separated by a thin layer of mesoglea, and includes filaments of tissue specialised for secreting digestive enzymes.
Sea anemones have soft tube like bodies. The external structure consists of the tentacles, the oral disk, and the pedal disk. can be found.The tentacles, which are covered in nematocysts, capture and transport prey to the oral disk. The oral disk serves as both the mouth and the anus. The mouth is the opening to the coelenteron, a single sac like cavity that performs all digestive functions. The pedal disk attaches the sea anemone to hard surfaces. The internal structure of a sea anemone consists of the contracting muscles, the gonads, the acontial filaments, and the ostium. The retracting muscles consist of simple longitudinal fibers that contract to move the anemone vertically. The sphincter muscles allow the tentacles to close over the oral disk. The gonads can be found in the mesentery. The ostium are where water is let in and out of the anemone. The acontial filament are found in the bottom sac section of the coelenteron. The acontial filaments are laden with nematocysts. Acontia filaments are used for protection from predators.
Sea anemones are flower-like. Anemones range in size from less than 1¼ centimeters (½ inch) to nearly two meters (six feet) in diameter.
A sea anemone is basically the typical polyp: a small sac, attached to the bottom by an adhesive foot, with a column shaped body ending in an oral disc. The mouth is in the middle of the oral disc, surrounded by tentacles. Anemones have a range of ten tentacles to hundreds. (Wikipedia)
Left: Sea Anemone, these simple invertebrates are essentially tubelike animals. One end of an anemone’s body is attached to or dug into the seafloor, while the other hosts a mouth surrounded by tentacles. (National Geographic)
Right: A group of sea anemones When threatened, the sea anemone quickly retracts its tentacles into its body cavity and contracts into a tight ball.
Left: Sea anemones in an intertidal zone of Friday Harbor, in Washington.
Right: Sea anemone Tidal Pool, Shell Beach, California.
(Class: Anthozoa, Subclass: Hexacorallia, Order: Actiniaria, Suborder: Nyantheae, Infraorder: Thenaria, Family: Actiniidae, Genus: Anthopleura, Species: Anthopleura xanthogrammica) Anthopleura xanthogrammica, or the giant green anemone, is a species of intertidal sea anemone of the family Actiniidae. Other common names for this anemone include green surf anemone, giant green sea anemone, green anemone, giant tidepool anemone, solitary anemone, and rough anemone.
The column width and height can reach a maximum of 17.5 and 30 cm, respectively. The crown of tentacles can be as wide as 25 cm in diameter, while the column, itself, tends to be widest at the base in order to offer a more stable connection to the rocks. It has a broad, flat oral disk surface and no striping, banding, or other markings. (Wikipedia)
(Class: Anthozoa, Subclass: Hexacorallia, Order: Actiniaria, Family: Stichodactylidae, Genus: Heteractis, Species: Heteractis malu) Heteractis malu, also known as the malu anemone, delicate sea anemone or white sand anemone, is a species of sea anemone in the family Stichodactylidae.
This anemone has stout, sparse tentacles, almost always under 40mm in length, usually tipped with magenta colouration. These tentacles vary in length, even among a single radial row.
The column has a pale cream or yellow colouration, with patches of deep yellow or orange sometimes present. It remains buried in sediment up to the level of the oral disc. The oral disc grows to a maximum diameter of 200 mm, is brown or purplish, possibly with a white, radial pattern. It may sometimes be bright green, but this is rare. (Wikipedia)
(Class: Anthozoa, Subclass: Hexacorallia, Order: Actiniaria, Family: Actiniidae, Genus: Entacmaea, Species: Entacmaea quadricolor) Entacmaea quadricolor, commonly called bubble-tip anemone among other vernacular names, is a species of sea anemone in the family Actiniidae. Like several anemone species, E. quadricolor can support several anemonefish species, and displays two growth types based on where they live in the water column, one of which gives it the common name, due to the bulbous tips on its tentacles. (Wikipedia)
(Class: Anthozoa, Subclass: Hexacorallia, Order: Actiniaria, Family: Stichodactylidae, Genus: Heteractis, Species: Heteractis magnifica)
The magnificent sea anemone (Heteractis magnifica), also known as the Ritteri anemone, is a species of sea anemone belonging to the Stichodactylidae family native from the Indo-Pacific area.
The magnificent sea anemone is characterized by a flared oral disc which reaches between 20 and 50 centimeters in diameter but in some specimens this can reach one meter. The numerous tentacles are exceeding 8 centimeters long. Its scientific and vernacular names come from the bright (magnificent) color of the column, which is the visible outer structure when the animal retracts, and these range from electric blue to green, red, pink, purple or brown. (Wikipedia)
Heteractis magnifica has the basic morphology of most anemones, living its entire life in the polyp form (looking like a cylindrical column with tentacles). This species has a sticky foot on a pedal disc, and an oral disc which contains the mouth and surrounding tentacles. Heteractis magnifica is the second largest in size of all sea anemones. The oral disc reaches 1 m in diameter or can be as small as 1.25 cm. Typically H. magnifica is between 300 and 500 mm in diameter. The foot, which is used to anchor the animal to various hard surfaces, is also larger than most anemones. The oral disc of an anemone is a flat to slightly curved structure with a mouth in the center, used for both feeding and producing waste. The oral disc can be yellow, brown, or green and is often slightly elevated so that the mouth protrudes out.
Members of this species can also look like a ball if they contract their tentacles so that only a tuft of tentacles, if any, remain visible. (animaldiversity.org)
(Class: Anthozoa, Subclass: Hexacorallia, Order: Actiniaria, Suborder: Nyantheae, Infraorder: Thenaria, Superfamily: Acontiaria, Family: Nemanthidae, Genus: Nemanthus, Species: Nemanthus annamensis) Nemanthus annamensis, commonly known as the gorgonian wrapper, is a species of sea anemone found in central Indo-Pacific waters.
Nemanthus annamensis has a rather variably-shaped base and low, spreading column, widening slightly just below the oral disc. This bears 120 to 130 tentacles, the inner ones longer than the outer, and a slit-shaped mouth with two siphonoglyphs. The column and tentacles are white, yellowish or orange, variegated with dark patches, and the oral disc is semi-transparent.
Nemanthus annamensis is native to the Indo-Pacific area. It was first described from the Gulf of Tonkin: annamensis signifies "of Annam", a historical name for central and northern Vietnam. It has also been found in the Arabian Sea off the coast of Kenya. It is known as the "gorgonian wrapper" because of its habit of attaching itself by its base and wrapping itself around the branches of gorgonians.
(Class: Anthozoa, Subclass: Hexacorallia, Order: Actiniaria, Family: Hormathiidae Genus: Calliactis, Species: Calliactis parasitica) Calliactis parasitica is a species of sea anemone associated with hermit crabs. It lives in the eastern Atlantic Ocean and Mediterranean Sea at depths between the intertidal zone and 60 m (200 ft). It is up to 10 cm × 8 cm (3.9 in × 3.1 in) in size, with up to 700 tentacles, and is very variable in colour. The relationship between C. parasitica and the hermit crab is mutualistic: the sea anemone protects the hermit crab with its stings, and benefits from the food thrown up by the hermit crab's movements. (Wikipedia)
Lybia is a genus of small crabs in the family Xanthidae. Their common names include boxer crabs, boxing crabs and pom-pom crabs. They are notable for their mutualism with sea anemones, which they hold in their claws for defense. In return, the anemones get carried around which may enable them to capture more food particles with their tentacles. Boxer crabs use at least three different species of anemones, including Bundeopsis spp. and Triactis producta. The bonding with the anemone is not required for survival, however, and boxer crabs have frequently been known to live without them, sometimes substituting other organisms such as sponges and corals for the sea anemones. (Wikipedia)
Tube-dwelling anemones or ceriantharians look very similar to sea anemones, but belong to an entirely different order of anthozoans. They are solitary, living buried in soft sediments. Tube anemones live inside and can withdraw into tubes, which are composed of a fibrous material made from secreted mucus and threads of nematocyst-like organelles known as ptychocysts.
Ceriantharians have a crown of tentacles that are composed of two whorls of distinctly different sized tentacles. The outer whorl consists of large tentacles that extend outwards. These tentacles taper to points and are mostly used in food capture and defence. The smaller inner tentacles are held more erect than the larger lateral tentacles and are used for food manipulation and ingestion. (Wikipedia)
Cerianthids differ from anemones in several ways, such as there is no pedal attachment and the lower end of the tube is buried in the soft sediments. The tube is open at the base (anal pore) which allows for escape of water when the animal retreats into the tube.
Tube-dwelling-anemone (Ceriantharia) and Orange sea pen (Ptilosarcus gurneyi) at Monterey Bay Aquarium, California. Left imageRight image
Cerianthus is a genus of tube-dwelling anemones in the family Cerianthidae. Members of the genus are found worldwide. They are predators, scavengers and omnivores.
Members of this genus do not have a pedal disc with which to hold themselves in position. Instead they live semi-buried in soft substrate surrounded by a parchment-like tube which they secrete. This surrounds the whole anemone up to its crown of tentacles. Sand grains, debris and shell fragments usually stick to the outer side of the tube. When it is disturbed, the anemone retracts swiftly back into the tube. Some of the larger species can have a column of up to 25 inches (640 mm) in length. The longitudinal muscles in the trunk are powerful but the transverse ones are weak. The outer ring of tentacles are long and tapering. The tube is flexible and the anemone can extend its tentacles a surprisingly long way. The inner ring of tentacles surrounds the central mouth and assists in pushing food inside. (Wikipedia)
(Phylum: Cnidaria, Class: Anthozoa, Order: Ceriantharia, Family: Cerianthidae, Genus: Cerianthus, Species: Cerianthus membranaceus) Cerianthus membranaceus, the cylinder anemone or coloured tube anemone, is a species of large, tube-dwelling anemone in the family Cerianthidae. It is native to the Mediterranean Sea and adjoining parts of the northeastern Atlantic Ocean.
Cerianthus membranaceus is a large, tube-dwelling anemone. The oral disc can have a diameter of up to 40 cm (16 in). There are two whorls of tentacles, amounting to about two hundred tentacles in all. Those in the outer whorl are long and slender and armed with cnidocytes (stinging cells) and are used for catching prey. Tentacles in the inner whorl are shorter and function to transfer captured food to the central mouth. The tentacles are sometimes banded and come in an array of colours; white, yellow, orange, green, brown, blue, black, purple and violet. The colour of the inner whorl often contrasts with that of the outer whorl. (Wikipedia)
Corals are marine invertebrates in the class Anthozoa of phylum Cnidaria. They typically live in compact colonies of many identical individual polyps. The group includes the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton.
A coral "group" is a colony of myriad genetically identical polyps. Each polyp is a sac-like animal typically only a few millimeters in diameter and a few centimeters in length. A set of tentacles surround a central mouth opening. An exoskeleton is excreted near the base. Over many generations, the colony thus creates a large skeleton that is characteristic of the species. Individual heads grow by asexual reproduction of polyps. Corals also breed sexually by spawning: polyps of the same species release gametes simultaneously over a period of one to several nights around a full moon.
Although some corals can catch small fish and plankton, using stinging cells on their tentacles, most corals obtain the majority of their energy and nutrients from photosynthetic unicellular dinoflagellates in the genus Symbiodinium that live within their tissues. These are commonly known as zooxanthellae and the corals that contain them are zooxanthellate corals. Such corals require sunlight and grow in clear, shallow water, typically at depths shallower than 60 metres (200 ft). Corals are major contributors to the physical structure of the coral reefs that develop in tropical and subtropical waters, such as the enormous Great Barrier Reef off the coast of Queensland, Australia.
Other corals do not rely on zooxanthellae and can live in much deeper water, with the cold-water genus Lophelia surviving as deep as 3,000 metres (9,800 ft). Some have been found on the Darwin Mounds, north-west of Cape Wrath, Scotland. Corals have also been found as far north as off the coast of Washington State and the Aleutian Islands. (Wikipedia)
Corals are sessile animals in the class Anthozoa and differ from most other cnidarians in not having a medusa stage in their life cycle. The body unit of the animal is a polyp. Most corals are colonial, the initial polyp budding to produce another and the colony gradually developing from this small start.
In stony corals, also known as hard corals, the polyps produce a skeleton composed of calcium carbonate to strengthen and protect the organism. This is deposited by the polyps and by the coenosarc, the living tissue that connects them. The polyps sit in cup-shaped depressions in the skeleton known as corallites. Colonies of stony coral are very variable in appearance; a single species may adopt an encrusting, plate-like, bushy, columnar or massive solid structure, the various forms often being linked to different types of habitat, with variations in light level and water movement being significant. (Wikipedia)
In soft corals, there is no stony skeleton but the tissues are often toughened by the presence of tiny skeletal elements known as sclerites, which are made from calcium carbonate. Soft corals are very variable in form and most are colonial. A few soft corals are stolonate, but the polyps of most are connected by sheets of coenosarc. In some species this is thick and the polyps are deeply embedded. Some soft corals are encrusting or form lobes. Others are tree-like or whip-like and have a central axial skeleton embedded in the tissue matrix. This is composed either of a fibrous protein called gorgonin or of a calcified material. In both stony and soft corals, the polyps can be retracted, with stony corals relying on their hard skeleton and cnidocytes for defence against predators, with soft corals generally relying on chemical defences in the form of toxic substances present in the tissues known as terpenoids. (Wikipedia)
The polyps of stony corals (Subclass Hexacorallia) have six-fold symmetry while those of soft corals (Subclass Octocorallia) have eight. The mouth of each polyp is surrounded by a ring of tentacles. In stony corals these are cylindrical and taper to a point, but in soft corals they are pinnate with side branches known as pinnules. In some tropical species these are reduced to mere stubs and in some they are fused to give a paddle-like appearance. In most corals, the tentacles are retracted by day and spread out at night to catch plankton and other small organisms.
Anatomy of Colonial Hard Corals
Hard corals are those responsible for building coral reefs. The polyps of hard corals make a sturdy, protective shell out of calcium carbonate. They filter the bicarbonate and calcium ions out of the seawater, where they are in abundance. The lower portion of the polyp secretes the skeleton where it is attached to a rock or other hard surface. This process produces a cup, called the "calyx," in which the polyp sits. The walls surrounding the cup are called the "theca," and the floor is called the "basal plate." Thin septa arise from the basal plate and provide the polyp with increased surface area, structural integrity, and protection. When polyps are physically stressed, they contract into the calyx so that virtually no part is exposed above the skeletal platform. This protects the organism from predators and the elements. (www.peteducation.com)
The “Sea Change” exhibition Left imageRight image
Using her amazing hand-crafted ceramic coral sculptures, scientist-turned-artist Courtney Mattison is on an artistic mission to bring awareness to the precarious state of our coral reefs. In her latest art exhibition, "Sea Change", Mattison, who has been using her talent to call attention to ocean issues for years now, takes visitors through an eye-opening tour of coral reefs and their biggest threat: humans.
Mattison’s current art exhibition, held at the Virginia Museum of Contemporary Art, features an eight-foot-tall ceramic reef made of glazed stone and porcelain. She crafts all of her sculptures by hand. In her studio, which she refers to as her “inland sea studio,” she builds tentacles and cup corals out of porcelain, but uses clay stoneware sculpture for the bulkier pieces.
The “Sea Change” exhibition was held at the Virginia Museum of Contemporary Art in April 2016.
The Class Anthozoa also includes many kinds of corals, including many reef-building species. Reefs are formed by the calcareous skeletons of many generations of coral polyps. The polyps inabit only the surface of the reefs. These reefs are among the most productive environments of the world, housing thousands of species of fish and invertebrates, not to mention plants and protists. Like some anemones, many corals are inhabited by symbiotic algae called zooxanthellae. These photosynthetic algae are essential for those coral, which generally do not live at depths to which light does not penetrate. (The Animal Diversity Web)
Coral reefs are diverse underwater ecosystems held together by calcium carbonate structures secreted by corals. Coral reefs are built by colonies of tiny animals found in marine waters that contain few nutrients. Most coral reefs are built from stony corals, which in turn consist of polyps that cluster in groups. The polyps belong to a group of animals known as Cnidaria, which also includes sea anemones and jellyfish. Unlike sea anemones, corals secrete hard carbonate exoskeletons which support and protect the coral polyps. Most reefs grow best in warm, shallow, clear, sunny and agitated waters. (Wikipedia)
Scleractinia is an order of class Anthozoa (subclass: Hexacorallia) within the phylum Cnidaria. Scleractinia, also called stony corals or hard corals, are marine animals in the phylum Cnidaria that live on the seabed and build themselves a hard skeleton. The individual animals are known as polyps and have a cylindrical body crowned by an oral disc with a mouth and a fringe of tentacles. Although some species are solitary, most are colonial. The founding polyp settles on the seabed and starts to secrete calcium carbonate to protect its soft body. Solitary corals can be as much as 25 cm (10 in) across but in colonial species the polyps are usually only a few millimetres in diameter. These polyps reproduce by budding but remain attached to each other, forming a multi-polyp colony with a common skeleton, which may be up to several metres in diameter or height according to species.
The shape and appearance of each coral colony depends not only on the species, but also on its location, depth, the amount of water movement and other factors. Many shallow-water corals contain symbiont unicellular organisms known as zooxanthellae within their tissues. These give their colour to the coral which thus may vary in hue depending on what species of symbiont it contains. Stony corals are closely related to sea anemones, and like them are armed with stinging cells known as cnidocytes. Corals reproduce both sexually and asexually. Most species release gametes into the sea where fertilisation takes place, and the planula larvae drift as part of the plankton, but a few species brood their eggs. Asexual reproduction is mostly by fragmentation, when part of a colony becomes detached and reattaches elsewhere.
Scleractinians fall into one of two main categories:
Reef-forming or hermatypic corals, which mostly contain zooxanthellae;
Non-reef-forming or ahermatypic corals, which mostly do not contain zooxanthellae
In reef-forming corals, the endodermal cells are usually replete with symbiotic unicelular dinoflagellates known as zooxanthellae. There are sometimes as many as five million cells of these per 1 square centimetre (0.16 sq in) of coral tissue. The symbionts benefit the corals because up to 50% of the organic compounds they produce are used as food by the polyps. The oxygen byproduct of photosynthesis and the additional energy derived from sugars produced by zooxanthallae enable these corals to grow at a rate up to three times faster than similar species without symbionts. These corals typically grow in shallow, well-lit, warm water with moderate to brisk turbulence and abundant oxygen, and prefer firm, non-muddy surfaces on which to settle.
Most stony corals extend their tentacles to feed on zooplankton, but those with larger polyps take correspondingly larger prey, including various invertebrates and even small fish. In addition to capturing prey in this way, many stony corals also produce mucus films they can move over their bodies using cilia; these trap small organic particles which are then pulled towards and into the mouth. In a few stony corals, this is the primary method of feeding, and the tentacles are reduced or absent, an example being Acropora acuminata. Caribbean stony corals are generally nocturnal, with the polyps retracting into their skeletons during the day, thus maximising the exposure of the zooxanthallae to the light, but in the Indo-Pacific region, many species feed by day and night.
Non-zooxanthellate corals are usually not reef-formers; they can be found most abundantly beneath about 500 m (1,600 ft) of water. They thrive at much colder temperatures and can live in total darkness, deriving their energy from the capture of plankton and suspended organic particles. The growth rates of most species of non-zooxanthellate corals are significantly slower than those of their counterparts, and the typical structure for these corals is less calcified and more susceptible to mechanical damage than that of zooxanthellate corals. (Wikipedia)
Families of the order Scleractinia:
The World Register of Marine Species lists the following families as being included in the order Scleractinia:
Acroporidae, Agariciidae, Anthemiphylliidae, Astrocoeniidae, Caryophylliidae, Coscinaraeidae, Deltocyathidae, Dendrophylliidae, Diploastreidae, Euphylliidae,
Flabellidae, Fungiacyathidae, Fungiidae, Gardineriidae, Guyniidae, Lobophylliidae, Meandrinidae, Merulinidae, Micrabaciidae, Montastraeidae, Montlivaltiidae, Mussidae, Oculinidae, Pectiniidae, Pocilloporidae, Poritidae, Psammocoridae, Rhizangiidae,, Schizocyathidae, Siderastreidae, Stenocyathidae, Trochosmiliidae
Acroporidae (Staghorn corals)
Acroporidae is a family of small polyped stony corals in the order Scleractinia, class Anthozoa, phylum Cnidaria. The name is derived from the Greek "akron" meaning "summit" and refers to the presence of a corallite at the tip of each branch of coral. They are commonly known as staghorn corals and are grown in aquaria by reef hobbyists.
Its Genera includes Acropora, Anacropora, Astreopora, Enigmopora, Isopora, Montipora. (Wikipedia)
Acropora is a genus of small polyp stony coral in the family Acroporidae. Some of its species are known as table coral, elkhorn coral, and staghorn coral. Over 149 species are described. Acropora species are some of the major reef corals responsible for building the immense calcium carbonate substructure that supports the thin living skin of a reef. (Wikipedia)
Mussidae is a family of stony coral in the order Scleractinia. Brain coral is a common name for this family.
Members of this family are widely sought after for the reef aquarium trade
Its Genera includes:
(A) Colpophyllia, Diploria, Favia, Manicina, Mussismilia, Pseudodiploria in the Subfamily Faviinae and
(B) Isophyllia, Mussa, Mycetophyllia, Scolymia in the Subfamily Mussinae. (Wikipedia)
Favites is a genus of stony corals in the Merulinidae family. (Wikipedia)
The walls (the raised areas) are shared or fused. The walls are shaped more polygonal and uneven and are also higher than Favia.
Antipatharia is an order of class Anthozoa (subclass: Hexacorallia) within the phylum Cnidaria. Antipatharians, commonly known as black corals, are treasured by many cultures for medicinal purposes and to produce jewellery. Despite their economic and cultural importance, very little is known about the basic biology and ecology of black corals because most species inhabit deeper-water environments (>50m) which are logistically challenging to study. ... Antipatharians are generally found in areas with hard substrates, low-light and strong currents. Under favourable conditions, some black coral species form dense aggregations to the point of becoming ecologically dominant. Zooplankton appears to be the major component of the diet of black corals, which feed as suspension feeders and use mucus and nematocysts to capture their prey. ... Antipatharians are generally slow-growing and long-lived organisms with maximum longevities ranging from decades to millennia. (NCBI)
The black or thorny corals (Antipatharia) make up an order of about 230 recognized species, many found in deep water. The colonies often grow in whiplike or branching tree-like formations up to 6 meters tall, supported by a skeletons made of a hard protein called antipatharin. The skeletons of many species contain dark pigments, and most produce spine-like structures on the surface of the skeleton. Usually the polyps have six nonretractable tentacles, but they can have multiples of six up to 24, arranged in an irregular branching pattern; this is key to distinguishing these corals from the gorgonian corals (octocorals, having eight tentacles), which they otherwise resemble. (eol.org)
Hawaii designated black coral as the official state gem in 1987. Black corals are animals (Family Antipathidae) that live in colonies up to 6 feet high (1.8 meters), though individual polyps may be less than .04 inches (1 mm) in diameter. Polyps are cylindrical with six non-retractable tentacles armed with stinging cells. Named for their stiff black or brownish skeleton, black coral is related to sea anemones and stony corals. Sometimes called “little thorn corals” because of tiny spines found on the surface of the skeleton, black coral is often seen in jewelry. The living coral may be black, red, orange, brown, green, yellow, or white (depending on the species). (www.statesymbolsusa.org)
Order Antipatharia consists of two main groups: the black (thorny) corals and wire corals. The living organisms may be black, red, orange, brown, green, yellow, or white, but they possess a dark skeleton that is characteristic to every black coral.
(Phylum: Cnidaria, Class: Anthozoa, Order: Antipatharia, Family: Antipathidae, Genus: Cirrhipathes) Cirrhipathes is a genus of black coral from the family Antipathidae, Order Antipatharia. Coral species in this genus are commonly known as whip or wire corals because they often exhibit a twisted or coiled morphology. In addition to their colorful appearance, with colors ranging from yellow to red passing through blue and green, these species possess a dark skeleton that is characteristic to every black coral. (Wikipedia)
Corallimorpharia is an order of class Anthozoa (subclass: Hexacorallia) within the phylum Cnidaria.
They are mostly tropical, with a narrow column topped with a wide oral disc. The tentacles are usually short or very short, arranged in rows radiating from the mouth. Many species occur together in large groups. In many respects, they resemble the stony corals, except for the absence of a stony skeleton. They are also known as mushroom (false) corals, mushroom anemones or disc anemones. (Wikipedia)
Discosoma (synonym Actinodiscus)
(Phylum: Cnidaria, Class: Anthozoa, Order: Corallimorpharia, Family: Discosomatidae, Genus:Discosoma) Discosoma (synonym Actinodiscus), commonly known as mushroom (false) coral, mushroom anemone,or disc anemone, are a genus of Corallimorph commonly collected, worldwide, as an easy coral to grow in marine aquaria.
(Phylum: Cnidaria, Class: Anthozoa, Order: Corallimorpharia, Family: Ricordeidae, Genus: Ricordea, Species: Ricordea florida)
Ricordea florida is a flower animal of the order of the disc anemones (Corallimorpharia). The sessile animals live in shallow water regions of the Caribbean , in the Bahamas and on the coasts of Florida in depths up to 50 meters. Their extreme pigmentation is Ricordea florida become very popular with seawater aquarium.
The body of the coral is small and cylindrical. Ricordea florida reaches 7.5 cm in diameter. The fleshy body and tentacles can be found in a variety of colours, including purple, orange, green, blue and yellow. The tips of the tentacles and the mouth may be one or more different colours. The colour of Ricordea florida depends on various factors, including the depth at which their live, temperature, season, and other environmental factors. (Wikipedia and de.wikipedia.org)
(Phylum: Cnidaria, Class: Anthozoa, Subclass: Hexacorallia, Order: Corallimorpharia, Family: Corallimorphidae, Genus: Corynactis, Species: Corynactis californica) Corynactis californica is a bright red colonial anthozoan similar to sea anemones and scleractinian stony corals. Unlike the Atlantic true sea anemone, Actinia fragacea, that bears the same common name, strawberry anemone, this species is a colonial animal of the order Corallimorpharia. Other common names include club-tipped anemone and strawberry corallimorpharian. The anemone is known to carpet the bottom of some areas, like Campbell River in British Columbia, and Monterey Bay in California. (Wikipedia)
(Phylum: Cnidaria, Class: Anthozoa, Subclass: Hexacorallia, Order: Corallimorpharia, Family: Corallimorphidae, Genus: Corynactis, Species: Corynactis annulata) Corynactis annulata, the strawberry anemone, is a bright pink colonial anthozoan similar in body form to sea anemones and scleractinian stony corals. Unlike the true sea anemones, this species is a colonial animal of the order Corallimorpharia.
The strawberry anemone is a very distinctive small bright pink anemone having white knobs on the ends of its tentacle tips. It grows to a diameter of 1 centimetre (0.4 in). Green and reddish colour morphs are also known.
(Phylum: Cnidaria, Class: Anthozoa, Subclass: Hexacorallia, Order: Corallimorpharia, Family: Corallimorphidae, Genus: Corynactis, Species: Corynactis viridis)
This anemone is often found in very large aggregations in suitable habitats. This is a short and squat anemone with a smooth column. The anemone has up to 100 tentacles, each ending in a small knob. Corynactis viridis is brilliantly coloured and can be green, pink, red, orange or white in various combinations. Usually the disc, tentacles and tentacle tips are contrasting colours. (naturewatch.org.nz)
Zoantharia is an order of class Anthozoa (subclass: Hexacorallia) within the phylum Cnidaria. Zoanthids (order Zoantharia, also called Zoanthidea) are an order of cnidarians commonly found in coral reefs, the deep sea and many other marine environments around the world. These animals come in a variety of different colonizing formations and in numerous colors. They are among the most commonly collected coral in reef aquaria, easily propagating and being very durable in many water conditions. Zoanthids can be distinguished from other colonial anthozoans and soft coral by their characteristic of incorporating sand and other small pieces of material into their tissue to help make their structure (except for the family Zoanthidae). The main characteristic of the order is that their tentacles are organized in two distinct rows. (Wikipedia)
Zoanthids live in colonies as single polyps attached to a base made of a mass of tissue or pieces of sediments, sand, and rock. The zoanthid coral can be many different varieties of colors and the colonies have distinct shapes. The zoanthids appear to be quite adaptable and are found all around the world, but since they need sunlight to survive they are only found in the shallow areas of the ocean. They require sunlight because of their symbiotic relationship with single-celled photosynthetic algae which produce most of the zoanthids needed nutrients.
The shape of both the single polyps and the colonies of zoanthids depend on the environment around the coral, but the basic shape of zoanthids looks like a colony of sea anemones. They have tube-shaped bodies topped with a flat, tentacle-ringed mouth. (creationwiki.org)
Zoanthid coral, including members from the species Palythoa and Zoanthus, have some characteristics we associate with plants and some with animals. They grow in the ocean as a group, permanently attach to reefs, feed like anemones, and propagate like coral.
Zoanthid coral grows in a colony, which means a bottom mat connects many tubules. Each tubule, called a stolon, resembles a single anemone. A top section has a ring of short tentacles surrounding its central mouth. This top is held up by an elongated column of tissue like the stalk of a mushroom, and this in turn connects to the collective mat.
Colonies can be made up of dozens of such stolons, each 1 - 1.5 inches (2.5 - 3.8 cm), to form carpets on or around reefs. Zoanthid coral prefer to grown on pieces of broken off coral that collect in valleys on tidepools or the ocean floor, but they can also survive on sand and rocks. Zoanthid coral grows in seemingly disparate ways. Some stolons are male and female, and release sperm and eggs to get fertilized and grow into a whole new colony. However, an existing colony can also propagate by branching off new polyps, like coral, that start from the carpet and grow upwards.
Zoanthid coral, since it can't perambulate (move around), feeds off nutrients that drift through the current, called detritus. Detritus is miniature pieces of food other creatures don't even notice, like bits of algae, plankton, or waste. Other nutrients are extracted from photosynthetic algae that live on zoanthid coral, called zooxanthellae. However, zoanthid coral is also equipped with poisonous toxins that can sting other creatures from the tips of their tentacles. This is solely for protection, not to paralyze animals for food. (www.wisegeek.com)
Families and genera
The 7 families and 16 genera within the order Zoantharia are:
1) Abyssoanthidae -- Abyssoanthus
2) Epizoanthidae -- Epizoanthus
3) Hydrozoanthidae -- Hydrozoanthus and Terrazoanthus
4) Neozoanthidae -- Neozoanthus
5) Parazoanthidae -- Antipathozoanthus, Corallizoanthus, Isozoanthus, Mesozoanthus, Parazoanthus, and Savalia
6) Sphenopidae -- Palythoa and Sphenopus
7) Zoanthidae -- Acrozoanthu, Isaurus, and Zoanthus
World Register of Marine Species (15 décembre 2014):
Parazoanthidae -- Antipathozoanthus, Bullagummizoanthus, Corallizoanthus, Hurlizoanthus, Isozoanthus, Kauluzoanthus, Kulamanamana, Mesozoanthus, Parazoanthus, Savalia, Zibrowius. (fr.wikipedia.org/wiki/Parazoanthidae)
Coenenchyme is the common tissue that surrounds and links the polyps in octocorals. It consists of mesoglea penetrated by tubes (solenia) and canals of the gastrodermis and contains sclerites, microscopic mineralised spicules of silica or of calcium carbonate. (Wikipedia: Coenenchyme)
The pedal disk is the bottom surface which attaches the zoanthid to substrate.
Stolons are the matting tissue connections between the polyps.
The column stretches from the oral disk to the pedal disk.
The Oral disk is the the flattened upper surface with the mouth in the center and tentacles around the margin.
The Mouth is the opening to the gut.
The tentacular crown is the ring of tentacles or skirt.
Each individual lash on the skirt is a tentacle.
Characteristics of Zoanthids:
Zoanthids lives in colonies which have distinct shapes. The basic shape of zoanthids looks like a colony of sea anemones. The individual polyps connected to one another at the base by a sheet of tissue frequently (except Zoanthus sp.) embedded with sand or other materials.
The central mouth is surrounded by a ring of smooth tentacles. There are two rows of tentacles. Tentacles usually very short and of equal length.
Distinguishing Zoanthus, Palythoa and Protopalythoa.
(Protopalythoa is no longer a valid genus, with all of its members now assigned to Palythoa.)
Members of Zoanthus do not incorporate sand and other debris into their coenenchyme, members of Palythoa do and their coenenchyme tissue is thicker and stronger. Their “skin” feels rougher to the touch. They are often “slimier” than Zoanthus due to a thicker mucus coating.
Generally speaking, Zoanthus have smaller polyps and oral disc. Palythoa generally have a larger polyps and oral disc than Zoanthus, with shorter tentacles. However, this is not always true.
Zoanthus also have more colorful polyps and oral disc, sometimes growing in bright colors of orange, blue, green, turquoise, red, etc. They are likely to have contrasting colors between the dull colors of tentacles and bright colors of the oral disk.
Protopalythoa have a larger oral disc than Palythoa with longer and sometimes greater number of tentacles. Their oral discs may be quite colorful under blue actinic lighting, even fluorescing, but their coenenchyme is normally brown or green in color.
The polyps of Zoanthus are embedded in the coenenchyme tissue and growing close to the mat. Palythoa also grow in a mat of coenenchyme with their polyps embedded. However, Palythoa use sediment to help reinforce their tissue and you can see sand, shell, or or other debris in their coenenchyme tissue. Protopalythoa have polyps on taller stalks that have more tentacles than the others.
Zoanthus have a distinct sphincter muscle around their oral opening. The others generally lack this characteristic. The Palythoa lack the sphincter muscle surrounding the oral opening, with many people describe this as a “slit” mouth instead of a “round” mouth for Zoanthus.
Palythoa tend to grow in dome shaped colonies. Protopalythoa are frequently found as solitary corals.
(References: Wikipedia, saltyunderground.com, and www.wildsingapore.com)
Stalk: an elongated, cylindrical part of the coral which holds up the polyp.
Stolon: the tissue which grows from the base of a polyp that grows into and fuses with neighboring polyps.
Mat: a common name for the thick tissue that resembles a solid sheet which connects all polyps in a coral colony.
Coenenchyme: the tissue tissue matrix that forms the stolon and the mat. When polyps are embedded in the coenenchyme without a stalk, the colony is typically considered massive. When the polyps are at the end of stalk, which emerges either from the coenenchyme, the colony is considered “connected”.
Mesoglea : the gelatinous substance of coenenchyme.
Sediment: small fragments of sand, shell, and other debris that absorbed into the coenenchyme of corals that strengthen the tissue.
(Phylum: Cnidaria, Class: Anthozoa, Subclass: Hexacorallia, Order: Zoantharia, Suborder: Brachycnemina, Family: Zoanthidae, Genus: Zoanthus) Zoanthus is a genus of Zoanthids in the family Zoanthidae.
Left: Zoanthus zanzibaricus in northeast Buliulin (south of the island Samama), Kalimantan, Berau islands, Indonesia.
Right: Zoanthus species Zoanthids Marine aquarium Neil Skene Australia
(Phylum: Cnidaria, Class: Anthozoa, Subclass: Hexacorallia, Order: Zoantharia, Family: Sphenopidae, Genus: Palythoa) Palythoa is a genus of Zoanthids in the family Sphenopidae.
The polyps of Palythoa are partially embedded in an encrusting mat of tissue (coenenchyme) covering the substrate on which the colony grows. The individual polyps have flattened oral discs surrounded by a fringe of tentacles. The tentacles' shape and size can vary considerably between species, and even between colonies of the same species. Their colors are also highly variable, with relatively dull shades like cream, coffee, white, brown, or yellow, being the most common. Fluorescent colored colonies also exist, but these are more rare. (Wikipedia)
The Palythoa lack the sphincter muscle surrounding the oral opening, with many people describe this as a “slit” mouth instead of a “round” mouth for Zoanthus.
Protopalythoa is no longer a valid genus, with all of its members now assigned to Palythoa. Protopalythoa often grow as solitary polyps, sometimes in small groups. They also have a larger oral disc than Palythoa with longer and sometimes greater number of tentacles.
(Phylum: Cnidaria, Class: Anthozoa, Subclass: Hexacorallia, Order: Zoantharia, Family: Parazoanthidae, Genus: Savalia, Species: Savalia savaglia) Savalia savaglia, the gold coral, is a species of colonial false black coral in the family Parazoanthidae. It is native to the northeastern Atlantic Ocean and the Mediterranean Sea where it often grows in association with a gorgonian. It is extremely long-lived, with a lifespan of 2,700 years, and develops into a large tree-like colony.
Savalia savaglia forms a large, tree-like colony. The polyps secrete a horny brown or black skeleton from which they project. They are yellow and about 3 cm (1.2 in) tall. Each polyp has an oral disc at the top surrounded by about thirty tentacles. These are arranged in two whorls and are not pinnate, making it easy to recognise that this species is a zoanthid rather than an octocoral or a member of another order of Hexacorallia.
The similarity it has with true black coral is the black color of the axial skeleton.
C -- in Balicasag Island, Cebu Strait, Philippines, 1999;
D -- in Tanjung Pandan, southwest of Pulau Panjang, east Kalimantan, Berau islands, 2003.
C -- Neozoanthus sp. in southwestern tip Tolandono island, Wakatobi National Park, Sulawesi, 2003;
D -- Neozoanthus sp. Bay Lembongan, Nusa Lembongan, Lombok Strait, 1998.
Left: Neozoanthus uchina in situ in the lower intertidal zone at Kamomine, Tokunoshima, Kagoshima, Japan, 2010.
A -- Partially closed polyps showing lack of encrustation at oral end.
B -- Colonies of two different color morphotypes.
C -- Close-up of polyps of the same color morphotype as on the left in B.
D -- Polyps showing variation in oral disk color where the dorsal directive is located.
Middle: Neozoanthus uchina in situ at Tebiro Beach, Amami-oshima, Kagoshima, Japan, 2011.
Right: Neozoanthus caleyi in situ around Heron Island on the Great Barrier Reef, Queensland, Australia.
A -- at Sykes Reef, depth=9 m, November 23, 2009
B -- Close-up of a single polyp showing yellow coloration at base of tentacles; at Sykes Reef, depth=18 m, November 18, 2009
C -- at Heron Channel, depth=23 m, November 24, 2009
D -- at Heron Channel, depth=approximately 20 m, November 2011.
Helioporacea is an order of class Anthozoa (subclass: Octocorallia) within the phylum Cnidaria. It consists of two families: Helioporidae and Lithotelestidae.
Helioporacea (Coenothecalia) forms massive lobed crystalline calcareous skeletons in colonial corals.
Heliopora coerulea (Blue coral)
The blue coral (Heliopora coerulea), the only species in the family Helioporidae, is most common in shallow water of the tropical Pacific and Indo-Pacific reefs. It has no spicules, and is the only octocoral known to produce a massive skeleton formed of fibrocrystalline aragonite fused into lamellae, similar to that of the Scleractinia (stony corals). They form large colonies that can exceed a meter in diameter. They are composed of vertical branches, or folia.
The surface of blue coral and similar species appears smooth and the color in life is a distinctive grey-brown with white tips. The entire skeleton, however, has an unusual blue color and therefore the species is commonly exploited for decorative uses. The blue color of the skeleton (which is covered with a layer of brown polyps) is caused by iron salts. Blue coral can be used in tropical aquaria, and the crystalline calcareous fibres in the skeletons can be used for jewelry.
Individual polyps have eight feathery tentacles and, in the gastrovascular cavity, eight septa, or partitions. Cilia (tiny hairlike projections) on six septa draw water into the cavity. Cilia on the other two septa expel water. The skeleton consists of spicules that form a protective cup around each polyp. (Wikipedia)
Blue coral (Heliopora coerulea) is the sole member in the family Helioporidae. Blue corals are named for their distinctive blue skeleton. When living, they look brown, because of the covering of living tissue. Polyps are minute, usually giving a slightly furry appearance. The polyps of the blue coral each have eight tentacles Each polyp contains eight tentacles, thus, placing this coral in the suborder Octocorallia. Iheir skeleton is made of crystalline aragonite, instead of the calcium carbonate that composes most of stony coral skeletons. Blue corals form branching, plate-like or columnar colonies. .
Alcyonacea is an order of class Anthozoa (subclass: Octocorallia) within the phylum Cnidaria.
The Alcyonacea, or soft corals, are an order of corals which do not produce calcium carbonate skeletons. Soft corals contain minute, spiny skeletal elements called sclerites, useful in species identification. Sclerites give these corals some degree of support and give their flesh a spiky, grainy texture that deters predators. In the past soft corals were thought to be unable to lay new foundations for future corals, but recent findings suggest that colonies of the leather-coral genus Sinularia are able to cement sclerites and consolidate them at their base into alcyonarian spiculite, thus making them reef builders.(Wikipedia)
Like the stony corals, Soft Corals are Cnidarians, meaning stinging celled animals. The familiar aquarium soft corals belong in the Family Alcyoniidae under the Alcyonacea Order. These are considered to be the "true" soft corals, yet they are just a part of this very large group. The Alcyonacea Order itself is part of the Subclass Octocorallia, known as Octocorals, and this entire subclass is also often loosely referred to as "soft corals".
The Alcyonacea order consists of hundreds of animals. It is divided into several families and suborders that include not only the Soft Corals, which encompass the Leather Corals as well, but also the Gorgonians. (animal-world.com)
Suborders and families
Order: Alcyonacea - Includes the Soft Corals, Leather Corals, and Gorgonians (sea fans and sea whips)
The World Register of Marine Species lists the following suborders and families:
Family Alcyoniidae - These are soft corals that are mostly referred to as the Leather Corals. They are known for being thick and encrusting and for their leathery skin. They can grow very large and take on many forms. -------- The genus Alcyonium is extremely variable and can have many forms including branched, fingered, ridged, and lobed. Their colors are usually yellow, brown or grayish, but can be other hues as well, and very vibrant. Common names often reflect their shapes and colors including such things as Finger Leather Coral, Encrusting Leather Coral, Dead Man's Fingers, Hand Coral, and Seaman's Hand Coral.
Family Nephtheidae - These are some of the most colorful and ‘fluffy' of the soft corals. They can be bushy or tree-like and come in beautiful hues of red, pink, yellow, and purple. Being branched and tree-like, they are known by such names as Carnation Coral, Tree Coral, and Colt Soft Coral.
Family Xeniidae - This family has both pulsing and non-pulsing varieties. Their colors can be white, brown, or a blue hue. Many varieties have long feather-like tentacles and their polyps will pump water into the colony, creating a rhythmic pulsing motion. They are known by such names as Pulsing Xenia, Waving Hand Coral, Glove Coral, Pulse Coral, and Pom-Pom Xenia.
Families: Nidaliidae, Paralcyoniidae
Familiy Clavulariidae - This family consist of a quite a few diverse corals, contained in four subfamilies. Those most familiar in the aquarium belong in the Subfamily Clavulariinae, though this is a very ‘loosely' defined group. Their polyps can have long tall stalks, topped with either feathery tentacles are stark tentacles, but giving them the look similar to the feather duster worm. They have a poor record of survivability in the aquarium. Common names include Clove Polyps, Glove Polyps, Palm Tree Polyps, and Fern Polyps.
Families: Acrossotidae, Coelogorgiidae, Cornulariidae, Pseudogorgiidae, Tubiporidae
Familis: Acanthoaxiidae, Haimeidae, Viguieriotidae
(Wikipedia and animal-world.com)
Alcyoniidae (Leather Corals)
(Phylum: Cnidaria, Class: Anthozoa, Order: Alcyonacea, Suborder Alcyoniina, Family: Alcyoniidae)
These are soft corals that are mostly referred to as the Leather Corals.
A colony of leathery coral is stiff, hard and inflexible. It is composed of tiny polyps projecting from a shared leathery tissue. Members of the family may have two kinds of polyps; the autozooids have long trunks and eight tiny branched tentacles and project from the shared leathery tissue while the siphonozooids remain below the surface and pump water for the colony. They appear as tiny hollows or mounds among the taller autozooids. Different genera have different proportions of these two kinds of polyps. The autozooids only emerge when the colony is fully submerged. (Wikipedia)
These are soft corals that are mostly referred to as the Leather Corals. They are known for being thick and encrusting and for their leathery skin. They can grow very large and take on many forms. -------- The genus Alcyonium is extremely variable and can have many forms including branched, fingered, ridged, and lobed. Their colors are usually yellow, brown or grayish, but can be other hues as well, and very vibrant. Common names often reflect their shapes and colors including such things as Finger Leather Coral, Encrusting Leather Coral, Dead Man's Fingers, Hand Coral, and Seaman's Hand Coral.(animal-world.com)
(Phylum: Cnidaria, Class: Anthozoa, Order: Alcyonacea, Suborder Alcyoniina, Family: Nephtheidae)
Nephtheidae is a family of soft corals in the phylum Cnidaria, class Anthozoa, order Alcyonacea. Members of this family are known as carnation corals, tree corals or colt soft corals. They are very attractive and show a wide range of rich and pastel colours including reds, pinks, yellows and purples. They are popular with reef aquarium hobbyists.
Most of these corals are arborescent and have little knobs on the end of their rubbery branches. The coral polyps tend to retract in the daytime which gives these corals their alternative name of broccoli corals because of their resemblance to the vegetable. At night the polyps emerge and extend their tentacles to feed, looking like little bunches of flowers on the ends of the branches. (Wikipedia)
These are some of the most colorful and ‘fluffy' of the soft corals. They can be bushy or tree-like and come in beautiful hues of red, pink, yellow, and purple. Being branched and tree-like, they are known by such names as Carnation Coral, Tree Coral, and Colt Soft Coral.
(Phylum: Cnidaria, Class: Anthozoa, Order: Alcyonacea, Suborder Stolonifera, Family: Clavulariidae) Clavulariidae is a family of soft corals in the suborder Stolonifera. Colonies in this family consist of separate retractable polyps growing from a horizontal, encrusting stolon or basal membrane. The tissues are stiffened by sclerites.(Wikipedia)
This family consist of a quite a few diverse corals, contained in four subfamilies. Those most familiar in the aquarium belong in the Subfamily Clavulariinae, though this is a very ‘loosely' defined group. Their polyps can have long tall stalks, topped with either feathery tentacles are stark tentacles, but giving them the look similar to the feather duster worm. They have a poor record of survivability in the aquarium. Common names include Clove Polyps, Glove Polyps, Palm Tree Polyps, and Fern Polyps.(animal-world.com)
Clavularia is a genus of corals in the Clavulariidae family. They are often referred by the common names, star polyps or glove polyps.
Left: Clavularia species
Right: Clavularia crassa consists of extended and retracted polyps.
Clavularia crassa forms small colonies of up to about fifty individual polyps growing from a stolon. This grows along the surface of the substrate and it, and the bases of the polyps, are orangish-brown. Each polyp is up to 10 mm (0.4 in) long and 2 mm (0.1 in) wide. The column is slender and creamy-white and the eight long, feathery tentacles are either transparent white, or colourless flecked with white. The oral surface is stiffened by calcareous sclerites. (Reference: Wikipedia Clavularia crassa)
Knopia is a genus of corals in the Clavulariidae family.
Left: Knopia octocontacanalis
Right: Knopia octocontacanalis Exploratory dive, Great Barrier Reef, near Port Douglas, Australia.
It looks like an impressionist painting of a field of daisies, but these are actually animals, the polyps of a soft octocoral, living some 12 metres beneath the sea near Port Douglas, Australia. The genus Knopia was first described only in January 2007 and is named after German marine biologist Daniel Knop, who supplied the type specimen. Knopia octocontacanalis is the only current member of the genus.
The name "Gorgonacea" is no longer considered valid and Alcyonacea is now the accepted name for the order.
(Phylum: Cnidaria, Class: Anthozoa, Subclass: Octocorallia, Order: Alcyonacea) Gorgonians are also known as sea whips and sea fans.Individual tiny polyps form colonies that are normally erect, flattened, branching, and reminiscent of a fan. Others may be whiplike, bushy, or even encrusting. A colony can be several feet high and across but only a few inches thick. They may be brightly coloured, often purple, red, or yellow.
The structure of a gorgonian colony varies. In the suborder Holaxonia, skeletons are formed from a flexible, horny substance called gorgonin. The suborder Scleraxonia variety of gorgonians are supported by a skeleton of tightly grouped calcareous spicules. There are also species which encrust like coral. Most of Holaxonia and Sclerazonia, however, do not attach themselves to a hard substrate. Instead, they anchor themselves in mud or sand.
Sea fan (genus Gorgonia): any member of a genus of invertebrate marine animals of the suborder Holaxonia (class Anthozoa, phylum Cnidaria). It is a variety of coral composed of numerous polyps—cylindrical sessile (attached) forms—that grow together in a flat fanlike pattern. Each polyp in the colony has eight tentacles. A central internal skeleton, composed of a flexible, horny scleroprotein called gorgonin, supports all branches of the colony, and the living tissues form a layer over its entire surface. The tissues are often coloured in hues of red, yellow, or orange. The polyps spread out their tentacles to form a plankton-catching net. In most cases the fan-shaped colonies grow across the current, which increases their ability to ensnare prey. (Encyclopædia Britannica)
Sea whip: any of several genera of corals of the order Gorgonacea (phylum Cnidaria), characterized by a long, whiplike growth and a variety of bright colours. The “whip” consists of a colony of tiny polyps (cylindrical, stalklike forms with a mouth and eight tentacles at the upper, or free, end) that grow upon one another in a continuous single stem. Spicules, or needlelike structures, of lime embedded in the polyp body provide a firm but flexible support.
Classification and Characteristics:
Order: Alcyonacea - Includes the Soft Corals, Leather Corals, and Gorgonians (sea fans and sea whips)
(1) Suborder: Holaxonia
The axial skeleton of Gorgonians in the suborder Scleraxonia are calcium based like other Octocorals. They have sclerites that are fused, or mostly fused, in their axis, their rind, and sometimes in their polyps.
Families: Acanthogorgiidae, Ainigmaptilidae, Chrysogorgiidae,
Red Gorgonian Leptogorgia chilensis (Synonym: Lophogorgia chilensis)
Purple Sea Blade, Angular Sea Whip Pterogorgia anceps
Bushy Sea Rod Rumphella sp.
Families: Ifalukellidae, Paramuriceidae, Plexauridae (Purple Bush, Rough Sea Plume Muriceopsis flavida), Parisididae.
(2) Suborder: Scleraxonia
The axial skeleton of Gorgonians in the suborder Holaxonia is composed of a fibrous protein substance, known as gorgonin. It is similar to the horn material of mammals. Thus the common names, Gorgonian, Horn Coral or Horny Coral, are derived from this substance.
Families: Anthothelidae (Finger Sea Fan Diodogorgia nodulifera, Encrusting Gorgonian Erythropodium caribaeorum)
Corky Sea Finger (Purple Corky Finger) Briareum asbestinum
Pacific Encrusting Gorgonian Briareum stechei
Families: Coralliidae, Keroeididae, Melithaeidae (Splendid Knotted Fan Coral Acabaria splendens)
Families: Paragorgiidae, Parisididae, Subergorgiidae
Gorgonians have a central stem that is tough, yet very flexible. It is covered with a living surface called a rind. The stem attaches to the substrate, with the delicate branches radiating outward. The suborder Holaxonia are composed of a fibrous protein substance, known as gorgonin, which is similar to the horn material of mammals. The common names, Gorgonian, Horn Coral or Horny Coral, are derived from this substance. Those in the suborder Scleraxonia are calcium based similar to other Octocorals. (animal-world.com)
(Phylum: Cnidaria, Class: Anthozoa, Subclass: Octocorallia, Order: Alcyonacea, Suborder: Holaxonia)
Members of this suborder are sometimes known as gorgonians and include the sea blades, the sea fans, the sea rods and the sea whips. These soft corals are colonial, sessile organisms and are generally tree-like in structure. They do not have a hard skeleton composed of calcium carbonate but have a firm but pliable, central axial skeleton composed of a fibrous protein called gorgonin embedded in a tissue matrix, the coenenchyme. In some genera this is permeated with a calcareous substance in the form of fused spicules. Members of this suborder are characterized by having an unspiculated axis and often a soft, chambered central core. The polyps have eight-fold symmetry and in many species, especially in the families Gorgoniidae and Plexauridae, contain symbiotic photosynthetic algae called zooxanthellae. These soft corals are popular in salt water aquaria. (Wikipedia)
Gorgoniidae is a family of soft corals in the Suborder Holaxonia, It consists of multiple genera including Pinnigorgia, Leptogorgia, Gorgonia ........
Originally the members of the family Gorgoniidae included a much wider range of genera than it does now and was used for all of the horny Octocorallia. Now it is restricted to those species where the "calcareous spicules are less than 0.3 mm. in length, sculptured with regularly disposed girdles of complicated tubercles ('warts'), the anthocodiae are relatively unarmed, at most with but a few characteristically shaped flat rods en chevron beneath each tentacle, the horny axial cylinder is weakly loculated if at all, and is perforated by a relatively narrow, chambered central chord, and in which the branchlets are usually quite slender, with a thin cortex."
The polyps are retractable and the stems have an axis of the protein gorgonin surrounding a narrow, hollow, cross-chambered central core. (Wikipedia)
(Class: Anthozoa, Subclass: Octocorallia, Order: Alcyonacea, Suborder: Holaxonia, Family: Gorgoniidae, Genus: Gorgonia)
Left: Gorgonia flabellum Origin: Cuba. Isla Juventud. Fuera de Límites
Right: Gorgonia ventalina Origin: Cuba. Pinar del Río. María la Gorda
Plexauridae is a family of soft corals in the Suborder Holaxonia, It consists of multiple genera including Paramuricea, Eunicea, Bebryce ........
Members of the family Plexauridae have a branching colony form and many are known as sea rods or sea fans. The axial core of the coral skeleton is horny and hollow and contains no sclerites. This is covered by a layer of tissue called coenenchyme in which is embedded calcareous sclerites. (Wikipedia)
(Class:, Anthozoa, Subclass: Octocorallia, Order: Alcyonacea, Suborder: Holaxonia, Family: Plexauridae)
Left: Paramuricea clavata with polyps extended.
Right: Bebryce sulfurea Origin: Egypt. Red Sea. Hurghada. Gota Shab El Erg
(Class:, Anthozoa, Subclass: Octocorallia, Order: Alcyonacea, Suborder: Holaxonia, Family: Plexauridae)
Left: Plexaura homomalla Black sea rod
Right: Plexaurella nutans in the background An orange Elephant Ear sponge (Agelas clathrodes) at the Florida Keys National Maritime Sanctuary. In the background is a deep water sea fan (Iciligorgia schrammi), and the giant slit-pore sea rod (Plexaurella nutans). These soft corals are actually slow moving animals but are often mistaken for plants.
Scleraxonia is a suborder of order Alcyonacea, class Anthozoa, and phylum Cnidaria. (Wikipedia)
Melithaeidae is a family of corals in the suborder Scleraxonia. Members of the family are commonly known as sea fans and are found on reefs in the tropical regions of the Indo-Pacific.
The World Register of Marine Species includes the following genera in the family: Acabaria, Asperaxis, Clathraria, Melithaea, Mopsella, Pleurocoralloides, and Wrightella. (Wikipedia)
Calcaxonia is a suborder of Alcyonacea, class Anthozoa, and phylum Cnidaria. Its families include Chrysogorgiidae, Dendrobrachiidae, Ellisellidae, Ifalukellidae, Isididae, and Primnoidae. (Wikipedia)
Ellisellidae is a family of marine gorgonians belonging to the suborder Calcaxonia. The family includes 11 genera including Ellisella and Junceella.(Wikipedia)
Ellisella is commonly known as sea whip. Ellisella constitutes bushy shrub gorgonians which dominant color is brown to reddish and polyps are white with eight tentacles. Branches are more or less long according to the species, however, very few ramifications are observed in the genus. (Wikipedia)
Left: Ellisella elongate Origin: Pinar del Rio, Maria la Gorda, Cuba.
Middle Left: Sea Whip (Ellisella sp.) Sachiko, Bunaken Island, Sulawesi, INDONESIA
Middle Right: Ellisella schmitti (sinonym: Nicella schmitti)
Right: Sea whips (Ellisella) The top of West Pulley Ridge outside the Habitat Area of Particular Concern reveals a high diversity of plants and animals including dozens of sponges, lettuce algae (Anadyomene) far left, crustose coralline algae encrusting the rocks, sea whips (Ellisella) and black fan corals (Antipathes). Photo credit: Coral Ecosystem Connectivity 2014 Expedition.
Junceella spp, along with the species of the genus Cirrhipathes in the order Antipatharia (Black coral), are commonly called wire coral, coral whip or sea whip. (Wikipedia)
Chrysogorgiidae is a family of marine gorgonians belonging to the suborder Calcaxonia.(Wikipedia)
Colonies structures comprise spiral or helical . The structure of the axis is branching Monopodial , and branches, not divided, only grow in the upper plane.
The polyps are short, about 3 mm and 1.5 mm in diameter, and have eight tentacles. Usually orange, yellow or white, aligned on the branches grow, also in a single plane and evenly spaced. (Wikipedia)
Left: Iridigorgia sp Gulf of Mexico (Credit: Image courtesy of Aquapix and Expedition to the Deep Slope 2007)
Middle Left: Iridogorgia sp Vailulu'u Expedition 2005. Pillow lavas on the western rift of Vailulu'u colonized with a large gorgonian, Iridogorgia sp., and a purple comatulid crinoid. (Credit: Image courtesy of Vailulu'u 2005 Exploration, NOAA-OE)
Middle Right: Iridogorgia, a spiral shaped coral as seen on Alvin dive 3901
Right: Iridogorgia magnispiralis
The colonies form tree-like structures. The structure of the axis consists of a stem, at the end, or around it, with a regular pattern spiral, grow branches, subdivided into branching dichotomous . This skeleton is highly calcified, also composed of gorgonin , and has a metallic characteristic golden color.
The polyps are short, between 1 and 3 mm, and have eight tentacles. Usually pink, yellow or white, grow on the branches, spaced regularly or irregularly, depending on the species. Often at the end of the branches. (Wikipedia)
Pennatulacea is an order of class Anthozoa (subclass: Octocorallia) within the phylum Cnidaria. It includes the sea pens, sea pansies, and veretillids, as well as a few species commonly called sea whips or sea feathers. Some of the first-described pennatulaceans were called sea pens or sea feathers because of their resemblance to quill pens (pinnate or penniform in appearance); this was the derivation of the group name Pennatulacea (from the Latin penn or pinna for feather, pen, or wing). However, only a few taxa are feather-shaped; many others are sausage-shaped, flattened and foliate, narrow and whiplike, or even shaped like palm trees. Pennatulaceans are benthic marine animals, as are all corals. However, they are unusual among corals in that the vast majority of species can anchor in soft sediments, such as mud, sand, fine rubble, or abyssal ooze, on the sea bottom, ranging from intertidal flats to the deep sea. Pennatulaceans are a highly specialized group of octocorals and differ markedly from soft corals and sea fans with regard to their colonial structure and habitat utilization. Morphologically, they are highly diverse, with perhaps 300 or more valid species in 35 genera of 14 families. (www.accessscience.com)
Sea pens are colonial marine cnidarians belonging to the order Pennatulacea. Although named after their feather-like appearance reminiscent of antique quill pens, only sea pen species belonging to the suborder Subselliflorae live up to the comparison. Those belonging to the much larger suborder Sessiliflorae lack feathery structures and grow in club-like or radiating forms. The latter suborder includes what are commonly known as sea pansies.
As octocorals, sea pens are colonial animals with multiple polyps (which look somewhat like miniature sea anemones), each with eight tentacles. Unlike other octocorals, however, a sea pen's polyps are specialized to specific functions: a single polyp develops into a rigid, erect stalk (the rachis) and loses its tentacles, forming a bulbous "root" or peduncle at its base. The other polyps branch out from this central stalk, forming water intake structures (siphonozooids), feeding structures (autozooids) with nematocysts, and reproductive structures. The entire colony is fortified by calcium carbonate in the form of spicules and a central axial rod.
Using their root-like peduncles to anchor themselves in sandy or muddy substrate, the exposed portion of sea pens may rise up to 2 metres (6.6 ft) in some species, such as the tall sea pen (Funiculina quadrangularis). Sea pens are sometimes brightly coloured; the orange sea pen (Ptilosarcus gurneyi) is a notable example. Rarely found above depths of 10 metres (33 ft), sea pens prefer deeper waters where turbulence is less likely to uproot them. Some species may inhabit depths of 2,000 metres (6,600 ft) or more.
The sea pansy is a collection of polyps with different forms and functions. A single, giant polyp up to two inches in diameter forms the anchoring stem (peduncle). This peduncle can be distended to better anchor the colony in the substrate. The pansy-like body bears many small, anemone-like feeding polyps. A cluster of tentacleless polyps form an outlet valve that releases water to deflate the colony. If the colony is on a sand bar at low tide, it usually deflates and becomes covered with a thin film of silty sand. Small white dots between the feeding polyps are polyps that act as pumps to expand the deflated colony. The feeding polyps secrete a sticky mucus to trap tiny organisms suspended in the water. The colony’s rigidity and purple color come from calcium carbonate spicules throughout the polyps tissues. (Wikipedia)
Sea pansies are fleshy, leaf-shaped colonies of marine organisms that belong to the genus Renilla, which is in the same Cnidaria phylum as jellyfish and corals. In fact, they are not a flower, but are actually a type of soft coral known as Pennatulacea. They are considered aggregate organisms, which is a colony made up of numerous individuals.
Colonies of sea pansies consist of stalks formed by large organisms called primary polyps, which can be up to 2 inches (5.08 cm) in diameter. These primary polyps have a fleshy structure called a peduncle that extends from the bottom of the main colony. The peduncle thrusts itself in the sand to anchor the pansies to the ocean floor.
The pansy-like body that gives the sea pansies their name is actually made up of various types of smaller, secondary polyps. Some of these secondary polyps are responsible for feeding the pansy. These feeding polyps extend above the sand and secrete sticky mucus to snare any tiny zooplankton and organic matter that venture nearby. Each feeding polyp sends its food to a common digestive system so the entire colony feasts or starves together. (www.wisegeek.com)
Sea pens are colonial marine cnidarians belonging to the order Pennatulacea. There are 16 families within the order; they are thought to have a cosmopolitan distribution in tropical and temperate waters worldwide. Sea pens are grouped with the octocorals ("soft corals"), together with sea whips or gorgonians. Although named after their feather-like appearance reminiscent of antique quill pens, only sea pen species belonging to the suborder Subselliflorae live up to the comparison. Those belonging to the much larger suborder Sessiliflorae lack feathery structures and grow in club-like or radiating forms. The latter suborder includes what are commonly known as sea pansies. (Wikipedia)
(Phylum: Cnidaria, Class: Anthozoa, Subclass: Octocorallia, Order: Pennatulacea, Family: Renillidae, Genus: Renilla)
The sea pansy is a colonial cnidarian native to warm continental shelf waters of the Western Hemisphere.
The Sea Pansy is a collection of polyps having different forms and functions. A single, giant polyp up to two inches in diameter forms the anchoring stem (peduncle). (Wikipedia)
The colony consists of a stalk formed by a large organism called a primary polyp that is thrust into soft bottom material; the upper part of the stalk is composed of several kinds of secondary polyps. Unlike true sea pens, sea pansies lie flat on the substratum.
Left: Renilla reniformis (Sea Pansy)
The detailed image below graphically illustrate the many small, anemone-like feeding polyps. A cluster of tentacleless polyps form an outlet valve that releases water to deflate the colony. If the colony is on a sand bar at low tide, it usually deflates and becomes covered with a thin film of silty sand. Small white dots between the feeding polyps are polyps that act as pumps to expand the deflated colony. The feeding polyps secrete a sticky mucus to trap tiny organisms suspended in the water.
Right: Renilla reniformis (Sea Pansy) Ventral image.
Ctenophora (singular ctenophore, from the Greek κτείς kteis 'comb' and φέρω pherō 'carry'; commonly known as comb jellies) is a phylum of invertebrate animals that live in marine waters worldwide. Their most distinctive feature is the ‘combs’ – groups of cilia which they use for swimming – they are the largest animals that swim by means of cilia. Adults of various species range from a few millimeters to 1.5 m (4 ft 11 in) in size.
Like cnidarians, their bodies consist of a mass of jelly, with one layer of cells on the outside and another lining the internal cavity. In ctenophores, these layers are two cells deep, while those in cnidarians are only one cell deep. Some authors combined ctenophores and cnidarians in one phylum, Coelenterata, as both groups rely on water flow through the body cavity for both digestion and respiration. Increasing awareness of the differences persuaded more recent authors to classify them as separate phyla. (Wikipedia)
Ctenophores (phylum Ctenophora), also known as comb jellies, are marine invertebrates that have eight rows of comb-like cilia on their transparent, gelatinous bodies. They are the largest animal to use cilia for locomotion.
Superficially, ctenophores resemble jellyfish, which belong to the phylum Cnidaria. Indeed, the Ctenophores and the Cnidaria were formerly grouped together as Coelenterata. However, despite their appearance, ctenophores are zoologically not true jellyfish, not least because they lack the characteristic cnidocytes (specialized cells that carry stinging organelles) that characterize the Cnidaria.
The signature characteristic of ctenophores are the comb rows, whereby the closely-spaced cilia in each row, which are fused at the base, are arranged as a stack of combs, called comb plates or ctenes. The word ctenophore (pronounced without the c) comes from Greek, kteno-, kteis, "comb" and -phore, meaning "bearer." (New World Encyclopedia)
Phylum Ctenophora, which includes the comb jellies. differ from
true jellyfish in two major ways—they have only a medusa stage and
they have no cnidocytes. Their tentacles are covered with a sticky
substance that traps plankton, their main prey. Although
a comb jelly is only about 2.5 cm (1 in.) in diameter, its tentacles can
be 10 times as long. (shapeoflife.org)
Jellyfish and Comb Jellies (Cnidaria & Ctenophora)
Jellyfish and comb jellies are gelatinous animals that drift through the ocean's water column around the world. They are both beautiful—the jellyfish with their pulsating bells and long, trailing tentacles, and the comb jellies with their paddling combs generating rainbow-like colors. Yet though they look similar in some ways, jellyfish and comb jellies are not very close relatives (being in different phyla—Cnidaria and Ctenophora, respectively) and have very different life histories. (Smithsonian Ocean Portal)
Left: Phylum Ctenophora Diagram
Ctenophores are characterized by eight rows of cilia, which are used for locomotion. The cilia in each row are arranged to form a stack of combs, also called comb plates, or ctenes; thus the name ctenophore comes from the Greek, meaning "comb bearer". These cilia beat synchronously and propel ctenophores through the water although some species move with a flapping motion of their lobes or undulations of the body. Many ctenophores have two long tentacles, but some lack tentacles completely.
Right: Top view of Haeckelia rubra showing 8 bands with strips of combs
Haeck Elijah rubra is a species of the comb jellies ((Phylum: Ctenophora, Class: Tentaculata, Order: Cydippida, Family: Haeckeliidae, Genus: Haeck Elia)
The number of known living ctenophore species is uncertain, since many of those named and formally described have turned out to be identical to species known under other scientific names. Claudia Mills estimates that there about 100 to 150 valid species that are not duplicates, and that at least another 25, mostly deep-sea forms, have been recognized as distinct but not yet analyzed in enough detail to support a formal description and naming.
The traditional classification divides ctenophores into two classes, those with tentacles (Tentaculata) and those without (Nuda). The Nuda contains only one order (Beroida) and family (Beroidae), and two genera, Beroe (several species) and Neis (one species).
The Tentaculata are divided into the following eight orders:
Cydippida, egg-shaped animals with long tentacles
Lobata, with paired thick lobes
Platyctenida, flattened animals that live on or near the sea-bed; most lack combs as adults, and use their pharynges as suckers to attach themselves to surfaces
Ganeshida, with a pair of small lobes round the mouth, but an extended pharynx like that of platyctenids
Thalassocalycida, with short tentacles and a jellyfish-like "umbrella"
Cestida, ribbon-shaped and the largest ctenophores
(Phylum: Ctenophora, Class: Tentaculata, Order: Cydippida, Family: Mertensiidae, Genus: Mertensia, Species: Mertensia ovum). The morphology of order Cydippida is characterized by egg-shaped body with long tentacles. Mertensia ovum aka the Arctic comb jelly or Sea Nut, is a cydippid comb jelly or ctenophore first described as Beroe ovum by Johan Christian Fabricius in 1780. Unusually among ctenophores, which normally prefer warmer waters, it is found in the Arctic and adjacent polar seas, mostly in surface waters down to 50 metres (160 ft).
In addition to being weakly bioluminescent in blues and greens, comb jellies produce a rainbow effect similar to that seen on an oil slick, and which is caused by interference of incident light on the eight rows of moving cilia or comb rows which propel the organism. The comb rows beat sequentially, rather like the action of a Mexican wave. The comb rows also function as chemical sense organs, serving the same role as insect antennae. Mertensia ovum is the major source of bioluminescence from Arctic gelatinous zooplankton. (Wikipedia)
One of the most delightful characteristics of ctenophores is the light-scattering produced by beating of the eight rows of locomotory cilia, which appears as a changing rainbow of colors running down the comb rows. Many people assume that they are seeing bioluminescence when they see this rainbow-effect, but really this is simple light diffraction or scattering of light by the moving cilia. Most (but not all) ctenophores are also bioluminescent, but that light (usually blue or green) can only be seen in darkness. (faculty.washington.edu)
(Phylum: Ctenophora, Class: Tentaculata, Order: Cydippida, Family: Aulacoctenidae, Genus: Aulacoctena) Mertensia ovum aka the Arctic comb jelly or Sea Nut, is a cydippid comb jelly or ctenophore first described as Beroe ovum by Johan Christian Fabricius in 1780. Unusually among ctenophores, which normally prefer warmer waters, it is found in the Arctic and adjacent polar seas, mostly in surface waters down to 50 metres (160 ft).
In addition to being weakly bioluminescent in blues and greens, comb jellies produce a rainbow effect similar to that seen on an oil slick, and which is caused by interference of incident light on the eight rows of moving cilia or comb rows which propel the organism. The comb rows beat sequentially, rather like the action of a Mexican wave. The comb rows also function as chemical sense organs, serving the same role as insect antennae. Mertensia ovum is the major source of bioluminescence from Arctic gelatinous zooplankton. (Wikipedia)
Left: Comb Jelly, Aulacoctena sp., a large softball-sized cydippid ctenophore from the deep waters of the Arctic Ocean. Alaska, Beaufort Sea, North of Point Barrow.
Right: Comb Jelly, Aulacoctena sp. This bright orange ctenophore in the genus Aulacoctena was observed at a depth of over 10,000 feet.
Mnemiopsis (Warty comb jelly)
(Phylum: Ctenophora, Class: Tentaculata, Order: Lobata, Family: Bolinopsidae, Genus: Mnemiopsis, Species: Mnemiopsis leidyi). The morphology of order Lobata is characterized with paired thick lobes.
The warty comb jelly or sea walnut (Mnemiopsis leidyi) is a species of tentaculate ctenophore (comb jelly), originally native to the western Atlantic coastal waters. Three species have been named in the genus Mnemiopsis, but they are now believed to be different ecological forms of a single species M. leidyi by most zoologists.
Mnemiopsis have a lobed body that is oval-shaped and transparent, with four rows of ciliated combs that run along the body vertically and glow blue-green when disturbed. They have several feeding tentacles. Unlike cnidarians, Mnemiopsis doesn't sting. Their body contains 97% water. They are small organisms, having a maximum body length of roughly 7–12 centimetres (3–5 in) and a diameter of 2.5 centimetres (1 in). (Wikipedia)
(Phylum: Ctenophora, Class: Tentaculata, Order: Lobata, Family: Lampoctenidae, Genus: Lampocteis, Species: Lampocteis cruentiventer)
Ranges in color from deep red, purple, or black to pale purple, always has a blood red stomach, hence the name. The cilia found on its combs appear to sparkle, due to reflection or refraction.
(Phylum: Ctenophora, Class: Tentaculata, Order: Thalassocalycida, Family: Thalassocalycidae, Genus: Thalassocalyce, Species: Thalassocalyce inconstans). Thalassocalycida is a monospecific order of ctenophore, or comb jellies, known from the California Coast, Gulf of Mexico, and west north Atlantic. The order was erected by description of Thalassocalyce inconstans collected in slope water off the coast of New England. T. inconstans is a pelagic ctenophore typically occurring in upper-mesopelagic depths, but has been observed at depths up to 3,500 m in Monterey Canyon.
Thalassocalyce inconstans is especially fragile having thin, flaccid tissues, likely contributing to broad under-sampling.
Thalassocalycid morphology is unique within the Ctenophora, sharing certain similarities to both cydippid (i.e. canal structure) and lobates, and characterized by absence of auricles and muscular lobes. Rather, unmuscular lobes are fused into a continuous dome forming a medusa-like body plan. (Wikipedia)
Left: Thalassocalyce This heart-shaped comb jelly, was among thousands of tiny creatures captured in an expedition conducted in 2006.
Right: The morphology of Thalassocalyce inconstans
A --Thalassocalyce inconstans in the open “bell” form, B -- “two globe” form; C -- oral view in the “two globe” form.
c canals, cr ctene rows, e edge of bell, g gut, m mouth, s statocyst, r ring muscle.
(Phylum: Ctenophora, Class: Nuda, Order: Beroida, Family: Beroidae) Nuda is a class of ctenophores or comb jellies. The class contains a single family, Beroidae, with two genera, Beroe and Neis, and the group is more commonly referred to as the "beroids". They are distinguished from other comb jellies by the complete absence of tentacles, in both juvenile and adult stages. Beroe is found in all the world's oceans and seas, and the monotypic Neis occurs only near Australia; all beroids are free-swimmers that form part of the plankton.
Some members of the diverse genus Beroe may occasionally attain a length of up to 30 centimetres (12 in), though most species and individuals are less than about 10 cm; Neis cordigera is among the largest species in the class, often exceeding 30 cm (12 in) in length. The body is melon or cone-shaped with a wide mouth and pharynx and a capacious gastrovascular cavity. Many meridional canals branch off this and form a network of diverticulae in the mesogloea. There are no tentacles but there are a row of branched papillae, forming a figure of eight around the aboral tip.
The sack-like body of the Beröe species may be cylindrical in cross section, or compressed to varying amounts according to species, while Neis is somewhat flattened and characterized by a pair of trailing gelatinous "wings" that extend beyond the aboral tip. (Wikipedia)
Left: Ctenophores, Beroe species
Right: Beroe cucumis
Body sack shape with a wide mouth at one end. No tentacles. Eight rows of hair-like cilia extend from the base to about three-quarters of the way to the mouth. Mature animals are pink. Body up to 15 cm long.