Antedon bifida
Encyclopedia
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.
grooves are on the upper surface of the disc. The arms can be up to 10cm (4in) 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.
south to Portugal
. 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 200m (650ft) and occasionally much deeper. It is often associated with other crinoid
s and bryozoans
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.
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. As well as crawling around, this feather star can swim short distances by flapping its arms.
A. bifida is dioecious
, each individual being either male or female. Gamete
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.
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.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of crinoid
Crinoid
Crinoids are marine animals that make up the class Crinoidea of the echinoderms . Crinoidea comes from the Greek word krinon, "a lily", and eidos, "form". They live both in shallow water and in depths as great as 6,000 meters. Sea lilies refer to the crinoids which, in their adult form, are...
in the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Antedonidae
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...
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 ambulacralAmbulacral
Ambulacral is a term typically used in the context of anatomical parts of the phylum Echinodermata or class Asteroidea and Edrioasteroidea. Echinoderms can have ambulacral parts that include ossicles, plates, spines, and suckers. For example, sea stars or "star fish" have an ambulacral groove on...
grooves are on the upper surface of the disc. The arms can be up to 10cm (4in) 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
Tube feet are the many small tubular projections found most famously on the oral face of a sea star's arms, but are characteristic of the water vascular system of the echinoderm phylum which also includes sea urchins, sand dollars and sea cucumbers and many other sea creatures.Tube feet function in...
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
Cirrus
Cirrus may refer to:In science:*Cirrus cloud, a type of cloud*Cirrus , a German research rocket*Cirrus, a fleshy, downward extension of the upper lip in salamanders or fish*Cirrus, a thoracic limb of an adult barnacle...
, 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
Antedon petasus is a marine invertebrate, a species of crinoid or feather star in the family Antedonidae. It is found in north west Europe.-Description:...
but that species is usually larger with up to 50 cirri, looks neater and does not have ridges on the undersides of its arms.
Distribution and habitat
A. bifida is primarily found on the coasts of north west Europe, the range extending from the Shetland IslandsShetland Islands
Shetland is a subarctic archipelago of Scotland that lies north and east of mainland Great Britain. The islands lie some to the northeast of Orkney and southeast of the Faroe Islands and form part of the division between the Atlantic Ocean to the west and the North Sea to the east. The total...
south to Portugal
Portugal
Portugal , officially the Portuguese Republic is a country situated in southwestern Europe on the Iberian Peninsula. Portugal is the westernmost country of Europe, and is bordered by the Atlantic Ocean to the West and South and by Spain to the North and East. The Atlantic archipelagos of the...
. 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 200m (650ft) and occasionally much deeper. It is often associated with other crinoid
Crinoid
Crinoids are marine animals that make up the class Crinoidea of the echinoderms . Crinoidea comes from the Greek word krinon, "a lily", and eidos, "form". They live both in shallow water and in depths as great as 6,000 meters. Sea lilies refer to the crinoids which, in their adult form, are...
s and bryozoans
Bryozoa
The Bryozoa, also known as Ectoprocta or commonly as moss animals, are a phylum of aquatic invertebrate animals. Typically about long, they are filter feeders that sieve food particles out of the water using a retractable lophophore, a "crown" of tentacles lined with cilia...
and may dominate its habitat. It moves from place to place, clinging to rocks, seaweed
Seaweed
Seaweed is a loose, colloquial term encompassing macroscopic, multicellular, benthic marine algae. The term includes some members of the red, brown and green algae...
and molluscs
Mollusca
The Mollusca , common name molluscs or mollusksSpelled mollusks in the USA, see reasons given in Rosenberg's ; for the spelling mollusc see the reasons given by , is a large phylum of invertebrate animals. There are around 85,000 recognized extant species of molluscs. Mollusca is the largest...
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 detritusDetritus
Detritus is a biological term used to describe dead or waste organic material.Detritus may also refer to:* Detritus , a geological term used to describe the particles of rock produced by weathering...
and plankton
Plankton
Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...
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
Cilium
A cilium is an organelle found in eukaryotic cells. Cilia are slender protuberances that project from the much larger cell body....
that line the groove. As well as crawling around, this feather star can swim short distances by flapping its arms.
A. bifida is dioecious
Dioecious
Dioecy is the property of a group of biological organisms that have males and females, but not members that have organs of both sexes at the same time. I.e., those whose individual members can usually produce only one type of gamete; each individual organism is thus distinctly female or male...
, each individual being either male or female. Gamete
Gamete
A gamete is a cell that fuses with another cell during fertilization in organisms that reproduce sexually...
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 symbioticSymbiosis
Symbiosis is close and often long-term interaction between different biological species. In 1877 Bennett used the word symbiosis to describe the mutualistic relationship in lichens...
relationship with the marine worm, Myzostoma cirriferum
Myzostomida
Myzostomida are a remarkable taxonomic group of small marine worms, which are parasitic on crinoids or "sea lilies", a kind of echinoderm. These unusual parasitic Lophotrochozoa were first discovered by Friedrich Sigismund Leuckart in 1827....
. 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
Metamorphosis is a biological process by which an animal physically develops after birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation...
and mature. They hold on with parapodial
Parapodium
Parapodia , singular parapodium, are paired, un-jointed lateral outgrowths from the bodies of two different invertebrate groups, which are primarily marine in habitat...
hooks and can move about on the host.