CLYPEASTER OR CAKE URCHIN

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CLASSIFICATION OF CLYPEASTER OR CAKE URCHIN

KINGDOM :- ANIMALIA (Multicellular eukaryotic organisms)

PHYLUM :- ECHINODERMATA (Coelomate, pentaradiate and spiny skinned animals with vascular system.)

SUB-PHYLUM :- ELEUTHEROZOA (Non-pedicellate and free-living.)

CLASS :-ECHINOIDEA (Body oval or spherical and composed of test)

SUB-CLASS :- IRREGULARIA (Periproct displaced towards mouth in innerradius.)

ORDER :- CLYPEASTEROIDA (Body disk-shaped, ambulacra petaloid and anus displaced laterally.)

GENUS :- Clypeaster (cake urchin)

It is found in tropical, sub-tropical region, Red Sea and North Carolina to Brazil.

Clypeaster is found creeping on the bottom or partly buried in sand. It shovels sand by its tube feet.

Commonly called as cake urchin.
Body is flattened and is exhibiting bilateral symmetry. Test is more or less round in outline and is covered with thick and short spines.
Body differentiated into oral and aboral surfaces.
Shell more or less five sided, each petaloid area being wide and well marked and each pair of ambulacral.
Aboral surface is slightly convex. Aboral ends of 5 ambulacral areas are bordered, each by two rows of flattened, respiratory tube feet, which are arranged in such a way that they appear like petals of flowers and are hence called as petaloids.
Madreporite is placed at the centre of the aboral side, from which radiate five petaloid ambulacral areas which are clearly seen. Between two petaloid is interambulacral area.
Oral surface is flat and covered by a dense velvety coat or short spines and pedicellariae. Mouth lies in centre and communicates with 5 simple groove along the centre of the ambulacral areas. Anus or periproct oral. Around mouth is 5 teeth of masticatory apparatus. Ambulacral groove is clearly seen.
At the beginning of each ambulacral area near the peristome there exist two sphaeridia which are immovable and devoid of nerve ring.
Genital plates are fused with the central pentagonal plate. Radial ocular plates are distinct.
Development includes echinopluteus larva.