AN ANTARCTIC SHELF POPULATION OF THE DEEP-SEA, PACIFIC BRACHIOPOD NEORHYNCHIA-STREBELI

Thirty-five specimens of the articulate brachiopod Neorhynchia strebel i were collected from a site at 814 m in the Weddell Sea. This was onl y the second species of the order Rhynchonellida to be found in Antarc tica. Formerly N. strebeli was known solely from abyssal Pacific Ocean localities. A circumantarctic distribution is suggested in addition t o the known deep-sea Pacific range. The specimens of this collection s howed considerable commissure variation, suggesting that the previousl y proposed erection of two subspecies on the basis of this character i s erroneous, and emphasises the phenotypic plasticity of some articula te brachiopods. The valve lengths and the number of alpha growth rings in the sample showed a normal distribution and a von Bertalanffy grow th function was fitted to the data: L-t = 23 (1-exp[-0.228t]). If the alpha growth rings were of annual periodicity, the ages attained by th e Antarctic N. strebeli of 11 y would be substantially lower than thos e reported for other Weddell Sea brachiopods. The epibiotic communitie s occurring on the valves of N. strebeli were impoverished, which is c haracteristic of deep water Antarctic brachiopods. The few specimens c ollected with their substratum were attached to small pebbles, but the typical attachment substrata may be different.