Legless Feather Star
Clarkcomanthus alternans
Its body is formed by a disc in the shape of a chalice, composed of 2 or 3 rings of calcareous plates, which houses inside the viscera of the animal. The centrodorsal plate measures about 5 mm in diameter. The anus and mouth are located on the tegmen, or aboral surface of the disc, which has a series of pinnules around it, whose terminal segments are modified to form a protective comb.
These crinoids have between 10 and 125 arms, which are pinnulated in the same plane, which gives them the appearance of feathers, hence one of the common names of crinoids in English: featherstar, or feathered star. The arms are composed of a series of ossicles, or jointed bones, called brachial, in addition to ligaments and muscles; and, in their interior they have extensions of the nervous, vascular and reproductive systems. In their case, the anterior arms are not clearly greater than the posterior ones.
The first series of ossicles, or primibraquial, is born from each of the five radial plates of each arm, the second series are born from the last ossicle of the primibrachial, from which two series, or secundibraquial, and so on.
In their aboral part, or inferior, they have elongated appendages to anchor themselves to the substrate, called "cirri". Specimens with less than 40 arms have about 11, which are composed of between 10 and 13 segments, called cirrales. Specimens with more than 40 arms lack cirri.
Like most crinoids, and many genera of the Echinodermata phylum, they have the ability to self-amputate an arm, in situations of danger to the animal. This faculty of some animals is called autotomy, and, in the case at hand, it is combined with another capacity, that of regenerating it completely afterwards. Frequently, replacing the amputated arm, they develop two new arms. Apart from the arms, they can also regenerate the cirri, the pinnules or the intestine.
To move they use cirri to "crawl" through the substrate, as well as the synchronized movement, and alternately, of their arms; They oscillate vertically from bottom to top, coordinated in three groups, managing to swim in this way.
This crinoid presents a great variety of colorations, being able to be black or mahogany, with the tips of the pinnulas in white or green; sometimes with a white line on the aboral part of the arm; dark brown with a fleck of small white or yellow dots; greenish yellow arms with groups of pnnules alternating black color with white and white tips with a central black line; and pale gray or white, with the pinnules in black or brown, and their tips in white.
They are located between 0 and 90 meters deep, anchored to hard corals, gorgonians or rocks, on the slopes of reefs, always in places with currents.
They are distributed in the western Pacific Ocean, in the Philippines, Indonesia, Palau, New Caledonia, Papua New Guinea and from Japan to Australia.
They are filtering, and are fed by tiny tubes of the brachial pinnules, which secrete a mucus to trap zooplankton, such as foraminifera, small crustaceans and mollusks, and phytoplankton.
They are dioic. The gonads are produced in specialized pinnules of the arms. Sexual reproduction is produced by external fertilization. Doliolar larvae evolve from bilateral symmetry to pentaradial symmetry, and have a stem, which they lose when they mature, becoming free-living animals.
These crinoids have between 10 and 125 arms, which are pinnulated in the same plane, which gives them the appearance of feathers, hence one of the common names of crinoids in English: featherstar, or feathered star. The arms are composed of a series of ossicles, or jointed bones, called brachial, in addition to ligaments and muscles; and, in their interior they have extensions of the nervous, vascular and reproductive systems. In their case, the anterior arms are not clearly greater than the posterior ones.
The first series of ossicles, or primibraquial, is born from each of the five radial plates of each arm, the second series are born from the last ossicle of the primibrachial, from which two series, or secundibraquial, and so on.
In their aboral part, or inferior, they have elongated appendages to anchor themselves to the substrate, called "cirri". Specimens with less than 40 arms have about 11, which are composed of between 10 and 13 segments, called cirrales. Specimens with more than 40 arms lack cirri.
Like most crinoids, and many genera of the Echinodermata phylum, they have the ability to self-amputate an arm, in situations of danger to the animal. This faculty of some animals is called autotomy, and, in the case at hand, it is combined with another capacity, that of regenerating it completely afterwards. Frequently, replacing the amputated arm, they develop two new arms. Apart from the arms, they can also regenerate the cirri, the pinnules or the intestine.
To move they use cirri to "crawl" through the substrate, as well as the synchronized movement, and alternately, of their arms; They oscillate vertically from bottom to top, coordinated in three groups, managing to swim in this way.
This crinoid presents a great variety of colorations, being able to be black or mahogany, with the tips of the pinnulas in white or green; sometimes with a white line on the aboral part of the arm; dark brown with a fleck of small white or yellow dots; greenish yellow arms with groups of pnnules alternating black color with white and white tips with a central black line; and pale gray or white, with the pinnules in black or brown, and their tips in white.
They are located between 0 and 90 meters deep, anchored to hard corals, gorgonians or rocks, on the slopes of reefs, always in places with currents.
They are distributed in the western Pacific Ocean, in the Philippines, Indonesia, Palau, New Caledonia, Papua New Guinea and from Japan to Australia.
They are filtering, and are fed by tiny tubes of the brachial pinnules, which secrete a mucus to trap zooplankton, such as foraminifera, small crustaceans and mollusks, and phytoplankton.
They are dioic. The gonads are produced in specialized pinnules of the arms. Sexual reproduction is produced by external fertilization. Doliolar larvae evolve from bilateral symmetry to pentaradial symmetry, and have a stem, which they lose when they mature, becoming free-living animals.