Feather star is a class of echinoderms (classified in the phylum Echinodermata, class Crinoidea) that are attached to sea bottom by a stalk root like branches. In adult stage they break away from stalk and move freely. Feather stars have ambulacra systems that extend into the branched arms on the crown. They are most of feather stars are found in shallow, warm waters.
The crinoid nervous system is divided into three parts, with numerous connections between them. The uppermost portion is the only one homologous with nervous systems of echinoderms. It consists of a central nerve ring surrounding the mouth. Below this lies a second nerve ring, giving off two brachial nerves into each arm. Both of these sets of nerves are sensory in nature. The third portion of the nervous system lies below the other two, and is responsible for motor action.
Feather stars feed on tiny organisms and particles from the water by adjusting their arms to maximize the filter feeding area. The arms may form a flat fan or curved like satellite dish. Some may hide in crevices and only stick out some part of their arms to gather food. The mucus covered arms have tiny tube that flick edible bits into the pinnacle and arm.
Crinoids are dioecious, with separate male and female. They are producing their gametes from genital canals found inside some of the pinnules. The pinnules eventually rupture to release sperm and eggs into sea water. The fertilized eggs hatch to release a free swimming vitellaria larva. While both feeding and non-feeding larvae exist among the four extant echinoderm classes, all present day crinoids appears to be descendant from surviving clad that went through bottleneck after the Permian extinction. The larva's...
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