About Echinaster callosus Marenzeller, 1895
Echinaster callosus grows to a maximum diameter of 26 cm (10 in). It has a small central disc and five slender, cylindrical arms. Its aboral (upper) surface is densely covered in warty protuberances. The colour of this starfish is variable, and can be orange, pink or violet, with warts in a contrasting colour, most commonly white, pink, red or mauve. White warts often form bands, particularly near the tips of the arms. Small yellowish-green retractable pedicellaria are located between the warts. The oral (under) surface of the starfish is white, and has white warts. Ambulacral grooves run along the underside of the arms, and food is moved along these grooves by ciliary action. The tip of each arm holds an eyespot, as well as a bundle of suckers. E. callosus is found in the tropical and subtropical western Indo-Pacific. Its range extends from East Africa and the Red Sea to Micronesia, and from Japan south to Australia and New Caledonia. It inhabits coral reefs and soft sediment, at depths between 5 and 30 m (20 and 100 ft). The creeping comb jelly Coeloplana astericola sometimes lives symbiotically on the aboral surface of this starfish, and also lives on the Luzon sea star, Echinaster luzonicus. Other associated organisms include small harmless worms and crustaceans, and the predators Charonia tritonis triton and Hymenocera picta harlequin shrimp, both of which feed destructively on the starfish's tissues.
