ARTIFICIAL DIETS IN SEA-URCHIN CULTURE - EFFECTS OF DIETARY-PROTEIN LEVEL AND OTHER ADDITIVES ON EGG QUALITY, LARVAL MORPHOMETRICS, AND LARVAL SURVIVAL IN THE GREEN SEA-URCHIN, STRONGYLOCENTROTUS-DROEBACHIENSIS

The effect of artificial diets on the size and energy content of eggs and morphometry, survival, and metamorphic success of larvae was inves tigated in the green sea urchin, Strongylocentrotus droebachiensis, fr om the standpoint of developing a good broodstock diet for culturists. Groups of sea urchins were fed eight diets over a period of 9 months, then five of these dietary groups were selected for detailed larval-g rowth studies. The artificial diets differed in protein content and in various additives including mannitol, algin, cholesterol, and beta-ca rotene; a diet of air-dried kelp was also included. Egg-energy content was highest on a high-protein diet with cholesterol and beta-carotene additives, and the largest eggs so far recorded for the species (2.39 mm(3) x 10(-3)) were produced on a high-protein diet with cholesterol additive. Larval survival to metamorphosis was (>92%) for all diets s ave for kelp (<5%). Kelp-fed adults also produced poorly metamorphosin g larvae (<2%), suggesting that air-drying causes chemical changes in the kelp that are ultimately detrimental to larval health. Larval deve lopmental rates were fastest on the high-protein beta-carotene formula tion. Larvae from this diet group also had the longest arms relative t o body length, largest rudiment diameter, largest absolute and relativ e ciliated-band length (for efficient feeding), and had a high percent age of metamorphosis. These data suggest that a high-protein beta-caro tene diet will be useful for conditioning broodstock by prospective se a urchin culturists.