GROWTH STUDIES WITH BACTERIA-FREE OYSTER (CRASSOSTREA GIGAS) LARVAE FED ON SEMI-DEFINED ARTIFICIAL DIETS

¹ College of Marine Studies, University of Delaware, Lewes, DE 19958

By the aseptic removal of gametes and in vitro fertilization of Crassostrea gigas eggs it was possible to obtain axenic larvae without the use of antibiotics. Optimal culture conditions for maintaining axenic larvae on algal diets have been developed.

Based on the results of ten growth experiments, C. gigas larvae fed on a semidefined biphasic artificial diet had a mean shell length of 96.0 µm (standard deviation ± 3.0 µm) after 6 days of growth. This was significantly greater (P < 0.001) than the mean shell length of starved larvae (79.8 ± 0.8 µm), but was significantly less (P < 0.001) than that of larvae fed on the alga Chaetoceros calitrans (113.6 ± 8.0 µm). C. gigas larvae grew on the dissolved organic fraction of the artificial diet alone, but growth was less than with the complete biphasic diet. This is the first reported demonstration that bivalve larvae can utilize dissolved nutrients for growth under axenic conditions where the possible nutritional contribution of bacteria is completely eliminated.