EchinodermsEchinodermata

Echinoderms are marine animals characterized by radial symmetry in their adult form and a calcareous endoskeleton, a name deriving from Greek for 'spiny skin'. Their body shapes vary widely, from the star-like forms of sea stars and brittle stars to the globular or discoidal bodies of sea urchins and sand dollars, or the elongated forms of sea cucumbers and crinoids. They move slowly using hydraulic tube feet, which also assist in feeding and respiration. Sizes range from a few millimetres in some brittle stars to over 1 metre (3.3 ft) in certain sea cucumbers.

Most species live on the seabed, ranging from intertidal zones to depths of several hundred meters in the 🌊 Red Sea. They are commonly encountered on most dives, found on reefs, sand, and rubble. Diets vary widely; some graze on algae, others filter plankton, and some are predators or detritivores. Many exhibit remarkable regenerative capabilities, able to regrow lost arms or even entire bodies from a single arm.