Rosy Feather Star, Antedon bifida
The rosy feather star (Antedon bifida) is a species of crinoid that can be found in northwestern waters of Europe. Its range extends from Portugal in the south to the Shetland Islands and includes Venezuela, West Africa, Algeria, and Tunisia. This species resides at an average depth of 650 feet, although it can occasionally be found in deeper waters.
The rosy feather star has a disc shaped body that is concave and holds ten arms that resemble a fern. These arms can grow to be ten inches long, although this size is not common. The under arms hold distinct ridges, and some are used for feeding or reproduction. Its pinnules, which are feather like organs, hold thirty-five segmented areas as well as uneven amounts of groupings of three tube feet. Its arms can vary in color from dark purple to yellow and can be spotted or blotched in appearance, while the pinnules are typically white in color. Underneath the body of this species are about twenty banded cirri, which act as legs and allow the creature to move around.
The rosy feather star is often found with other species of crinoids, as well as bryozoans, and is often the dominate species within its range. It is a mobile species, moving about and attaching itself to mollusks, rocks, and seaweed. It is typically found in areas with fast water currents, because it is able to attach itself to surfaces with its strong cirri.
The rosy feather star is known as a dioecious species, which means that every individual is either male or female. The spawning season of this species typically occurs between the months of May to July. During this time, females release eggs, which stick to the outside pinnules and await fertilization. After this, the female will close arms to protect the eggs, which are covered in a mucous like substance. The eggs hatch into larvae after forty-five days and will swim around until large enough to attach themselves to a nearby surface. Although the larvae are still small, they feed in a similar manner as adults. After developing their first cirri, they will detach themselves and move about, eventually reaching adult size.
The diet of the rosy feather star feeds on detritus and plankton, using its pinnules to catch the food that is floating by. If larger food is available, it will use two pinnules to bring the food into its largest set of tube feet in order to prevent the prey from escaping. Smaller particles stick to the mucous that forms on the smaller third foot and after the particles have accumulated enough, they are transferred into the mouth by cilia that appear along the groove of the foot.
The rosy feather star holds a symbiotic relationship with a marine worm known as Myzostoma cirriferum. Treated as food particles, the larvae of the worms become attached the feather star’s tube feet. They then move to the ambulacral grooves on the pinnules where they will undergo metamorphosis. After reaching their adult size, the worms are able to move around the feather star without falling off.
Image Caption: Pentacrinoid stage of Antedon bifida (Pennant, 1777); Antedonidae; a) arms: b) basals; r) radials; s) stalk. Credit: British Museum/Wikipedia