RAPID GROWTH OF A DEEP-SEA WOOD-BORING BIVALVE

The growth of Xylophaga atlantica Richards, a deep-sea wood-boring bivalve, was studied by recovering a 1-year time series of oak and pine panels deployed at depths of 100 and 200 m at the edge of the continental shelf, south of Cape Cod. Change in shell height between samples was used to assess growth rate. At the 100 m site, the first individuals to settle grew much faster, on average, than those that settled later in the year on the same panels (0.085 mm day-1 vs 0.031 mm day-1, respectively). The growth rate of the maximum sized individuals was 0.027 mm day-1 whereas the modal growth rate was half that at 0.015 mm day-1. The modal growth rate of those recovered from 200 m was much greater at 0.246 mm day-1 and is thought to be due to the warmer average temperatures there. Differences in growth rate due to season, substrate and previous density were also apparent.