The echinoderms (Greek for spiny skin) include sea stars, sea urchins, feather stars, brittle stars and sea cucumbers. All are found in the marine environment in a range of habitats from intertidal surf beaches to the deepest oceans. Sydney is home to about 120 species of echinoderms and, because of their size and unusual shapes, they are one of the easiest groups to find on the rocky shore.
Some echinoderms have excellent powers of regeneration. Sea stars often regrow arms bitten off by predators and, if disturbed, brittle stars drop off an arm or part of an arm. This allows them to escape predators as the cast-off arm continues to wriggle to distract the attention of the attacker.
Common features of all echinoderms are:
- an internal calcareous skeleton
- a water vascular system that operates their tube feet.