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Echinoderms possess a simple digestive system which varies according to the animal's diet. Starfish are mostly carnivorous and have a mouth, oesophagus, two-part stomach, intestine and rectum, with the anus located in the centre of the aboral body surface. With a few exceptions, the members of the order Paxillosida do not possess an anus.
Crinoids are echinoderms in the phylum Echinodermata, which also includes the starfish, brittle stars, sea urchins and sea cucumbers. [5] They live in both shallow water [6] and in depths of over 9,000 metres (30,000 ft). [7] Adult crinoids are characterised by having the mouth located on the upper surface.
Starfish are deuterostomes, closely related, together with all other echinoderms, to chordates, and are used in reproductive and developmental studies. Female starfish produce large numbers of oocytes that are easily isolated; these can be stored in a pre-meiosis phase and stimulated to complete division by the use of 1-methyladenine . [ 125 ]
The starfish is found on hard bottoms and under stones and seaweed where it mainly feeds on other echinoderms and on bivalve molluscs. [3] In most of its range, it undergoes sexual reproduction in the winter, while in the summer, it proliferates by asexual reproduction. [4]
Brittle stars, serpent stars, or ophiuroids (from Latin ophiurus 'brittle star'; from Ancient Greek ὄφις (óphis) 'serpent' and οὐρά (ourá) 'tail'; referring to the serpent-like arms of the brittle star) are echinoderms in the class Ophiuroidea, closely related to starfish. They crawl across the sea floor using their flexible arms ...
This is not, however, the case with echinoderms like starfish, sea urchins, and sea cucumbers. Instead, these creatures are driven by an unusual five-fold symmetry, also called radial symmetry ...
Together, the data created a 3D map to determine where genes were expressed as sea stars developed and grew. The team was able to determine the genes that control the development of the starfish ...
Sea urchins are members of the phylum Echinodermata, which also includes starfish, sea cucumbers, sand dollars, brittle stars, and crinoids. Like other echinoderms, they have five-fold symmetry (called pentamerism) and move by means of hundreds of tiny, transparent, adhesive "tube feet".