THE ECHINODERMATA - STARFISH, BRITTLE STARS, SEA URCHINS, SAND DOLLARS, SEA CUCUMBERS, AND CRINOIDS

The Phylum Echinodermata is named for the hard, often spiny outer covering. Uniquely they have tube feet controlled by a water vascular system. They are also radially symmetrical Quite a few different echinoderms are common at Station beach, notably several species of brittle stars (right), sea urchins, sand dollars, star fish, and sea cucumbers (below). They are exclusively marine and thought to share a common ancestor with the chordates to the exclusion of almost all other invertebrates.

Above, is the panamic brittle star, Ophioderma panamense.

The sulfur sea cucumber, Holothuria lubrica

The sea cucumbers belong to the Class Holothuria. They are still radially symmetrical but are elongate about the axis of symmetry and lack a hard shell. They often common under rocks and in tide pools. They feed on detritus and often disgorge there stomachs when disturbed.

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