Starfishes are echinoderms, the name indicating “spiny-skinned”. To the same group belong sea urchins and sea slugs. The most distinctive structure of an echinoderm is an elaborate water-pumping system which operates numerous feeler-like processes known as tube feet. These tube feet are very noticeable on the under side of a starfish, and they assist greatly in the locomotion of the animal. Many of our starfishes have distinctive shapes and are easily recognised. The Comb Star (Astropecten polyacanthus) is a perfect five pointer, 8–9 in. across, and is found on sandy bottom from low water to 30 fm. The pentagonshaped Cushion Star (Asterina regularis), 2–3 in. across and variously brightly coloured, is our most abundant intertidal species. The Spiny Star (Coscinasterias calamaria) grows to 15 in. across, usually has 11 arms, and is common in the intertidal zone in most parts of New Zealand. The common Brittle Star, one of many different local species, differs from other starfishes in having the organs of the body restricted to a small central disc. When disturbed these brittle stars readily shed limbs in their efforts to escape.
by Arthur William Baden Powell, Assistant Director, Auckland Institute and Museum.