Echinodermata Gen Characters 1

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#starfish #brittle star # sea cucumber #Sea urchin # Echine # Echino dermata # Holothuridians # Achrionoids #sea lilly # Tube feet #Madreporite #eater wascular system • Characteristic Features of Phylum Echinodermata. These are exclusively marine animals. The larval forms show bilateral symmetry and adult forms show radial symmetry. They are triploblastic. It exhibits organ system grade of organisation. They have a true coelom. The body is uniquely shaped. • (Echinos: Spines; derma: Skin) • Kingdom: Animalia • Habitat: These are exclusively marine • Grade of organization: organ system grade • Germ layer: triploblastic • Symmetry: Adults are radially symmetrical while the larvae are bilaterally symmetrical. • Coelom: present ( coelomate) • Body without segmentation • The shape of the body is flat, star like, spherical or elongated. • Head is absent • Presence of tube feet • Presence of water vascular system • Mouth is present on ventral side while anus is present on dorsal side • Respiration: by papule, gills or clocal respiratory tree • Nervous system: absent, they are brainless organism. • Circulatory system: is reduced, heart is absent • Blood has no pigment. • Digestive system: complete • Excretory system: absent • Sexes: mostly dioecious, rarely monocious • Reproduction: • Sexual: by gamatic fusion • Asexual: regeneration • Fertilization: external • Development: indirect with characteristic larvae • Classification of phylum Echinodermata • It is divided into 5 classes: • Asteroidea • Ophiuroidea • Echinoidea • Holothuroidea • Crinoidea • Class 1 Asteroidea • Body is flattened star shaped with five arms • They possesses tube feet with a sucker • Presence of calcareous plates and movable spines. • Respiratory organ: papulae • Examples: Asterias (Star fish), Astropecten, Zoraster, Oreaster • Class 2 Ophiuroidea • Body is flat with pentamerous disc • They possess a long arm which is sharply demarcated from the central disc. • They possesses tube feet without sucker • Anus and intestine are absent • Respiratory organ: Bursae • Examples: Ophiderma, ophiothrix, Astrophyton, Amphuria, etc • Class 3 Echinoidea • Body is disc-like hemi-spherical • They are devoid of arms or free-rays. • They possesses tube feet with a sucker. • They possess compact skeleton and movable spines. • Examples: Echinus (Sea urchin), Cidaris, Arbacia, Echinocardium. Diadema • Class 4 Holothuroidea • Body is elongated in the oral-aboral axis and it is like cucumber. • They have no arms, spines and pedicellariae. • The tube feet are sucking type which is modified into tentacles and form a circle around mouth. • Respiratory organ: cloacal respiratory tree • Examples: Cucumaria (Sea cucumber), Holothuria, Mesothuria, etc • Class 5 Crinoidea • Body is star shaped • Some of the forms were extinct and living forms. • Arms bifurcated, with two pinnules. • They have tube feet without suckers • Examples: Neometra, Antedon, Rhizocrinus, etc

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