Echinoderm is a Greek word which literally means “spiny skin”. There are about 6000 species of the phylum Echinodermata. Some of them are having spiny skin while some have not. They are only found in the sea. They are having radial symmetry. In multiples of five, their appendages usually occur. Sea stars and sea urchins are well known members of this group. Within the body of the animal, the water vascular system is also filled with sea water. Only their larvae are with bilateral symmetry. Suckers are present on their tube feet. They do not have brain while nerves are present that works like brain.
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