Rosy feather star, Antedon bifida
The Rosy feather star is a species of starfish in the Antedonidae family. It is found in North West Europe along the coast. The specific area of the coast is between the Shetland Islands south to Portugal. There have been sightings in Algeria, Tunisia, West Africa and Venezuela. The Western and Eastern coasts of the British Isles has a climate that promotes the growth of the Antedon bifida. It grows between the low tide mark and 650 feet deeper. Clinging to rocks, seaweed and mollusks, it moves from place to place and will dominate its habitat. Strong currents with both sheltered and exposed environments are this star’s favorite.
The fern-like body of the Rosy feather star is due to the ten arms or leaflets growing opposite each other in pairs around a concave disc. The arms grow to about 4 inches long but are commonly shorter. Feeding and reproduction takes place on the distinguished transverse ridges underneath the arms of the body. The pinnules (leaflets) have about 35 segments and are jointed; each leaflet has tubed feet. The tubed feet are grouped in three and vary in unequal lengths. The petal-like arms can be found in yellow, pink, and deep purple while the finger-like tubes are a paler white. The ossicle (stem) has about twenty short appendages arranged in transverse rows; this allows animals to crawl around the exterior.
The pinnules catch its food, known as suspension feeding. Dead organisms (Detritus) and plankton caught in the currents are the common food for the Antedon. The tubed feet catch larger particles while the smaller particles stick to the mucus. Once the particles are held together, the third “foot” helps bundle them into a bolus; a soft, roundish lump. The bolus is then moved to the surface of the concaved disc; this is where it is moved to the “mouth.” The feather star can flap its arms and swim short distances.
The Antedon is characterized as having both female and male organisms. A gamete, a cell fusing with another cell during fertilization, is produced between May and July. These gametes (eggs) are produced from the genital canals at the base of each arm. The fertilization happens on the outside of the leaflets with the eggs stuck to them. The female then produces a net of mucus to protect the embryos. The female cradles the embryos with her arms — some describe this as a brooding behavior. The eggs hatch in about five days and become free-swimming larvae and then settle on a solid surface; here is where they attach themselves with a short stem (pentacrinoid larvae stage). The larvae’s feeding system is much like that of the adult and they will develop clawed appendages and then detach from their stems. Maturity is achieved in one to two years.
Image Caption: Rosy feather star (Antedon bifida). Credit: British Museum/Wikipedia