Notes on the Biology of the Echinoid Diadema Antillarum

Randall, John; Schroeder, Robert; Starck, Walter

Looked at growth rates, predators, abundance, food, habitats and spawning of the long-spined sea urchin (Diadema antillarum) around St. John. Diodema antillarum, one of the most noxious of marine invertebrates of the West Indian region, occupies diverse habitats; it is known from the shore to 400 meters on rock, coral reef, mangrove roots, sea grass beds and sand. It is also abundant; average counts of 1.2 individuals per m2 were made on Thalassia beds in the Florida Keys, and 13.4 per m2 on a flat rocky shore of a sheltered bay in the Virgin Islands. Growth rates of 3.5 to 6.7 mm. in test diameter per month were recorded for three groups of juveniles 4 to 25 mm. in test diameter which were held in wire cages in the sea in the Virgin Islands. The intestinal contents of specimens from Thalassia beds in Florida consisted mostly of Thalassia. Thirteen observations were made of spawning or ripe Diadema in the Virgin Islands in all seasons of the year and with no apparent correlmion with the lunar cycle. Spawning occurs in such tightly packed groups that individual urchins may be lifted above the substratum on the interlocking spines of the others. Predators of D. antillarum include 15 fishes of the families Balistidae, Carangidae, Diodontidae, Labridae, Ostraciidae, Sparidae, and Tetraodontidae, two gastropods of the genus Cassis, and the spiny lobster (Panulirus argus). Mysid shrimps, the young of various West Indian fishes, and apogonid fishes as adults have been observed hiding among the spines of Diodema, and two species of palaemonid shrimps have been found living on the test and spines.

Notes on the Biology of the Echinoid Diadema Antillarum

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