''Antedon bifida'' is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

crinoid Crinoids are marine animals that make up the class Crinoidea. Crinoids that are attached to the sea bottom by a stalk in their adult form are commonly called sea lilies, while the unstalked forms are called feather stars or comatulids, which are ...

in the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Antedonidae Antedonidae is a family of crinoids or feather stars in the phylum Echinodermata. Members of the family are unstalked and have ten feathery arms. They can move about freely and have clawed cirri to attach them temporarily to structures.

commonly known as the rosy feather star. It is found in north west Europe.

Description

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 Ambulacral is a term typically used in the context of anatomical parts of the phylum Echinodermata or class Sea star, Asteroidea and Edrioasteroidea. Echinoderms can have ambulacral parts that include Ossicle (echinoderm), ossicles, plates, spines ...

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 Tube feet (technically podia) are small active tubular projections on the oral face of an echinoderm, whether the arms of a starfish, or the undersides of sea urchins, sand dollars and sea cucumbers; they are more discreet though present on britt ...

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 Giovanni Battista Cirri (1 October 1724 – 11 June 1808) was an Italian cellist and composer in the 18th century. Biography Cirri was born in Forlì in the Emilia-Romagna Region of Italy. He had his first musical training with his brother ...

, 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 ''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. Description ''A. petasus'' has a conical disc with five pairs of arms, each up to ...

'' but that species is usually larger with up to 50 cirri, looks neater and does not have ridges on the undersides of its arms.Feather Star (''Antedon bifida'')
Marine Species Identification Portal. Retrieved 2011-10-14.''Antedon bifida'' (Pennant, 1777)
National Museums of Northern Ireland. Retrieved 2011-10-14.Rosy feather-star - ''Antedon bifida''
Marine Life Information Network (MarLIN). Retrieved 2011-10-14.

Distribution and habitat

''A. bifida'' is primarily found on the coasts of north west Europe, the range extending from the

Shetland Islands Shetland, also called the Shetland Islands and formerly Zetland, is a subarctic archipelago in Scotland lying between Orkney, the Faroe Islands and Norway. It is the northernmost region of the United Kingdom. The islands lie about to the no ...

south to

Portugal Portugal, officially the Portuguese Republic ( pt, República Portuguesa, links=yes ), is a country whose mainland is located on the Iberian Peninsula of Southwestern Europe, and whose territory also includes the Atlantic archipelagos of ...

. It has also been reported from Algeria, Tunisia, West Africa and Venezuela. 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

s and

bryozoa Bryozoa (also known as the Polyzoa, Ectoprocta or commonly as moss animals) are a phylum of simple, aquatic invertebrate animals, nearly all living in sedentary colonies. Typically about long, they have a special feeding structure called a l ...

ns and may dominate its habitat. It moves from place to place, clinging to rocks,

seaweed Seaweed, or macroalgae, refers to thousands of species of macroscopic, multicellular, marine algae. The term includes some types of '' Rhodophyta'' (red), ''Phaeophyta'' (brown) and ''Chlorophyta'' (green) macroalgae. Seaweed species such as ...

and

molluscs Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant taxon, extant species of molluscs are recognized. The number of fossil sp ...

with its clawed cirri. It favours areas with strong currents in both sheltered and fairly exposed positions and is often found in gullies.

Biology

''A. bifida'' is a suspension feeder, catching

detritus In biology, detritus () is dead particulate organic material, as distinguished from dissolved organic material. Detritus typically includes the bodies or fragments of bodies of dead organisms, and fecal material. Detritus typically hosts commun ...

and

plankton Plankton are the diverse collection of organisms found in Hydrosphere, water (or atmosphere, air) that are unable to propel themselves against a Ocean current, current (or wind). The individual organisms constituting plankton are called plankt ...

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 The cilium, plural cilia (), is a membrane-bound organelle found on most types of eukaryotic cell, and certain microorganisms known as ciliates. Cilia are absent in bacteria and archaea. The cilium has the shape of a slender threadlike projecti ...

that line the groove. As well as crawling around, this feather star can swim short distances by flapping its arms. ''A. bifida'' is

dioecious Dioecy (; ; adj. dioecious , ) is a characteristic of a species, meaning that it has distinct individual organisms (unisexual) that produce male or female gametes, either directly (in animals) or indirectly (in seed plants). Dioecious reproductio ...

, each individual being either male or female.

Gamete A gamete (; , ultimately ) is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually. Gametes are an organism's reproductive cells, also referred to as sex cells. In species that produce t ...

s 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. Eventually they develop clawed cirri and become detached from their stalks, reaching maturity in one to two years.

Ecology

''A. bifida'' has a

symbiotic Symbiosis (from Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or parasit ...

relationship with the marine worm, ''

Myzostoma cirriferum ''Myzostoma'' is a genus of marine worms, which are parasitic on crinoids in the family Myzostomidae. Species The following species are classified in this genus: *'' Myzostoma abundans'' Graff, 1883 *'' Myzostoma adhaerens'' Remscheid, 1918 *'' ...

''. 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 Metamorphosis is a biological process by which an animal physically develops including birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation. Some inse ...

and mature. They hold on with parapodial hooks and can move about on the host.

References

External links

* {{Taxonbar, from=Q649919 Antedonidae Fauna of the Atlantic Ocean Animals described in 1777 Taxa named by Thomas Pennant