| Antedon bifida | |
|---|---|
 | |
| Pentacrinoid stage of Antedon bifida; a) arms: b) basals; r) radials; s) stalk | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Echinodermata |
| Class: | Crinoidea |
| Order: | Comatulida |
| Family: | Antedonidae |
| Genus: | Antedon |
| Species: | A. bifida |
| Binomial name | |
| Antedon bifida | |
| Synonyms [1] | |
| |
Antedon bifida is a species of crinoid in the family Antedonidae commonly known as the rosy feather star. It is found in north west Europe.
The body of A. bifida is a concave disc surrounded by ten pinnately divided arms giving it a fern-like appearance. The mouth and ambulacral grooves are on the upper surface of the disc. The arms can be up to 10 cm (4 in) long but are usually shorter than this. The undersides of the arms have prominent transverse ridges and some have modifications for feeding and reproduction. The pinnules are jointed, have about 35 segments and bear unequal sized tube feet in groups of three. The arm colour is variable, ranging from yellow or pink to deep purple, sometimes spotted or blotched, and the pinnules are usually paler or white. There are about twenty short cirri, banded and arranged in transverse rows on a central raised ossicle. These curl under and grasp the surface enabling the animal to crawl around which it can do with great rapidity. It may be confused with the rather similar Antedon petasus but that species is usually larger with up to 50 cirri, looks neater and does not have ridges on the undersides of its arms. [2] [3] [4]
Antedon bifida is primarily found on the coasts of north west Europe, the range extending from the Shetland Islands south to Portugal. [2] It has also been reported from Algeria, Tunisia, West Africa and Venezuela. [1] Around the British Isles it is found on north eastern and on western coasts. It occurs from the low tide mark to a depth of about 200 m (650 ft) and occasionally much deeper. It is often associated with other crinoids and bryozoans [2] and may dominate its habitat. It moves from place to place, clinging to rocks, seaweed and molluscs with its clawed cirri. It favours areas with strong currents in both sheltered and fairly exposed positions and is often found in gullies. [3] [4]
Antedon bifida is a suspension feeder, catching detritus and plankton with its pinnules as they float past. Larger particles are captured and held by the two larger tube feet of each group of three. Small particles adhere to the mucus they extrude and the smaller third foot helps to bundle these together to form a bolus. The food is then transferred to the ambulacral groove where it is moved towards the mouth by the current created by the cilia that line the groove. [5] As well as crawling around, this feather star can swim short distances by flapping its arms. [6]
Antedon bifida is dioecious, each individual being either male or female. Gametes are produced, mostly between May and July, from the genital canals found at the base of some arms. The eggs stick to the outside of the pinnules where fertilisation takes place. The female produces a mucus net and protects the developing embryos by holding her arms together in what is described as brooding behaviour. After about five days, the eggs hatch into free-swimming larvae which soon settle on a solid surface and attach themselves with a short stalk. Now known as pentacrinoid larvae, they have a similar feeding system to that of the adults. [5] Eventually they develop clawed cirri and become detached from their stalks, reaching maturity in one to two years. [4]
Antedon bifida has a symbiotic relationship with the marine worm, Myzostoma cirriferum . The worm larvae are caught by the tube feet of the feather star and treated like food particles. They attach in the ambulacral grooves of the pinnules where they undergo metamorphosis and mature. They hold on with parapodial hooks and can move about on the host. [7]
An echinoderm is any deuterostomal animal of the phylum Echinodermata, which includes starfish, brittle stars, sea urchins, sand dollars and sea cucumbers, as well as the sessile sea lilies or "stone lilies". While bilaterally symmetrical as larvae, as adults echinoderms are recognisable by their usually five-pointed radial symmetry, and are found on the sea bed at every ocean depth from the intertidal zone to the abyssal zone. The phylum contains about 7,600 living species, making it the second-largest group of deuterostomes after the chordates, as well as the largest marine-only phylum. The first definitive echinoderms appeared near the start of the Cambrian.
Crinoids are marine invertebrates that make up the class Crinoidea. Crinoids that remain attached to the sea floor by a stalk in their adult form are commonly called sea lilies, while the unstalked forms, called feather stars or comatulids, are members of the largest crinoid order, Comatulida. Crinoids are echinoderms in the phylum Echinodermata, which also includes the starfish, brittle stars, sea urchins and sea cucumbers. They live in both shallow water and in depths over 9,000 metres (30,000 ft).
Articulata are a subclass or superorder within the class Crinoidea, including all living crinoid species. They are commonly known as sea lilies or feather stars. The Articulata are differentiated from the extinct subclasses by their lack of an anal plate in the adult stage and the presence of an entoneural system. Articulata first appeared in the fossil record during the Triassic period although other, now extinct crinoid groups, originated in the Ordovician.
Antedon is a genus of sessile, stemless crinoids. The genus first appeared in the fossil record in the Cretaceous period.
Antedon petasus is a marine invertebrate, a species of crinoid or feather star in the family Antedonidae. It is found around the coasts of north west Europe.
Comatulida is an order of crinoids. Members of this order are known as feather stars and mostly do not have a stalk as adults. The oral surface with the mouth is facing upwards and is surrounded by five, often divided rays with feathery pinnules. Comatulids live on the seabed and on reefs in tropical and temperate waters.
Davidaster rubiginosus, the orange sea lily, is a species of crinoid in the family Comatulidae. At one time it was classified as Nemaster rubiginosa but the World Register of Marine Species has determined that the valid name is Davidaster rubiginosus. It is found on reefs in the tropical western Atlantic and the Caribbean Sea.
Davidaster discoideus, the beaded crinoid, is a species of feather star in the family Comatulidae. It was previously known as Nemaster discoidea but the World Register of Marine Species has determined that the valid name is Davidaster discoideus. It is found on reefs in the Caribbean Sea and northern coast of South America.
Comaster schlegelii, the variable bushy feather star, is a crinoid in the family Comatulidae. It was previously classified as Comanthina schlegeli but further research showed that it was better placed in the genus Comaster. It is found on shallow water reefs in the western Pacific Ocean.
Metacrinus rotundus, the Japanese sea lily, is a species of stalked crinoid in the family Isselicrinidae. It is a species found off the west coast of Japan, near the edge of the continental shelf at a depth of around 100 to 150 metres deep. This is the shallowest-living species among the extant stalked crinoids.
Anneissia bennetti, the Bennett's feather star, is a species of crinoid belonging to the family Comatulidae. It is found in shallow water in the Indo-Pacific between northern Australia and southeast Asia.
Antedon mediterranea is a species of stalkless crinoid in the family Antedonidae, commonly known as the Mediterranean feather star. It is found on the seabed at moderate depths in the Mediterranean Sea. It is a filter feeder and captures plankton with its long feathery arms.
Ptilometra australis, the passion flower feather star, is a species of crinoid. It is native to the coasts of southeastern Australia where it is found on reefs, in estuaries and bays at depths down to about 110 metres (360 ft).
Leptometra celtica is a marine invertebrate and species of crinoid or feather star of the Leptometra genus in the family Antedonidae. It is found in the Atlantic Ocean around the coasts of north west Europe. The presence of L. celtica and L. phalangium is considered to be a good indication of nearby shelf breaks, general bottom currents, and areas of high gross productivity as they are suspension-feeders, hence their proliferation in productive environments.
Florometra serratissima is a species of crinoid or feather star in the family Antedonidae. It is found off the Pacific coast of North America, usually in deep water.
Promachocrinus kerguelensis is a species of free-swimming, stemless crinoids. It was the only member of its genus until several species were discovered in 2023. P. keruguelensis a coldwater crinoid which is found in the seas around Antarctica and surrounding island groups, including under the sea ice.
Aporometra wilsoni is a marine invertebrate, a species of crinoid or feather star in the family Aporometridae. It is found in shallow water around the coasts of southern Australia.
Notocrinus virilis is a marine invertebrate, a species of crinoid or feather star in the family Notocrinidae. It is found in deep water in the Southern Ocean around the coasts of Antarctica and adjacent islands. A sea snail sometimes parasitizes it.
Aporometra paedophora is a marine invertebrate, a species of crinoid or feather star in the family Aporometridae. It was first found at a depth of 22 fathoms off the Manning River on the New South Wales coast. Other specimens were found off the coast of Bunbury, Western Australia at depths between 9 and 15 m. Based on morphological evidence of four specimens of A. paedophora, Helgen & Rouse believe that this may not be a separate species from Aporometra wilsoni.
Cenometra bella is a species of crinoids belonging to the genus Cenometra. They can have up to 30 arms and can be of variable colours but are often characterised by a marked contrast between the extending free-arms and the feathery pinnules. This species clings to its support and moves around by its feet-like cirri.