Sea urchins (Latin Echinoidea) - class of echinoderms. Described about 940 modern species. The body of sea urchins are usually nearly spherical, ranging in size from 2-3 to 30 cm, covered with rows of calcareous plates. The plates are usually connected to stationary and form a dense shell (shell) that does not allow a hedgehog to change form. The shape of the body (and some other grounds), sea urchins are divided into right and wrong. In regular urchins body shape is almost round, and they are built on strictly a five-way radial symmetry. In irregular sea urchins flattened body shape, and they are distinguishable front and back ends of the body.

With the shell of sea urchins movably connected (through the joint capsule with muscle fibers) needles of various lengths. The length varies from 1-2 mm (flat-urchins, Echinarachniidae) up to 25-30 cm (diademovye urchins, Diadematidae). There is a kind, completely devoid of needles - toksopneustes (Toxopneustes), whose body is dotted with peditsellyariyami. Needles are often sea ezham for movement, nutrition and protection. Some species are poisonous needles, as connected with special venom glands. Poisonous species (Asthenosoma, Diadema) distributed mainly in tropical and subtropical areas of the Indian, Pacific and Atlantic oceans, including in the Red Sea.

In addition to needles, on the surface of the shell of sea urchins sitting peditsellyarii, as well as at the mouth opening, the special organs of balance - sferidii. In some species peditsellyarii also equipped with venom glands (Toxopneustes, Sphaerechinus).
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You can see the sea urchins in shallow water on the beaches of Hurghada, Safaga, Sharm el Sheikh, as well as on coral reefs.