GROWTH OF POST-SET OYSTERS, CRASSOSTREA-VIRGINICA, ON HIGH-LIPID STRAINS OF ALGAL FLAGELLATES TETRASELMIS SPP

Nine microalgal strains from the prasinophyte genus Tetraselmis that w ere chosen for high total lipid content, and one marine strain of the chlorophyte Chlamydomonas, were compared with Isochrysis sp., strain T -ISO, as diets for oyster spat in a controlled laboratory feeding expe riment. Five of these high-lipid Tetraselmis strains supported signifi cantly faster oyster growth than an equivalent ration of T-ISO. Doubli ng times for oyster weight, volume, and shell height were in the range of 1.5-3 weeks on single daily feedings of the best diets, Tetraselmi s strains yielding the most rapid oyster growth contained higher conte nts of the essential fatty acid 20:5n-3 and of the sterols 24-methylch olesterol and/or 24-methylenecholesterol. These data are consistent wi th our earlier findings that these compounds appear to be deficient in most phytoplankton for optimal growth of Crassostrea virginica spat.