Evaluation of partial substitution of live algae with dried Tetraselmis for larval rearing of black-lip pearl oyster, Pinctada margaritifera (L.)

Abstract

Experiments were conducted with larvae of the black-lip pearl oyster, Pinctada margaritifera fed on a regime of living algae(an equal mixture of Tahitian Isochrysis aff. galbana and Pavlova salina)either partially or completely substituted with heterotrophically grown spray-dried algae (Tetraselmis suecica). Two experiments were conducted; in the first, 1-day old larvae were cultured for 13 days and, in the second, 13 days old larvae were culture for 7 days. In both experiments larvae were fed the following proportions of live algae (LA) and dried Tetraselmis (DT); (1) 100% LA, (2) 75% LA +25% DT, (3) 50% LA + 50% DT, (4) 25% LA +75% DT; and (5) 100% DT. The optimal diets for maximum larval growth were 100% LA and75% LA + 25% DT resulting in larvae with a mean shell length (SL) of 132 ± 3.8 and 131± 2.7 µm, respectively, at day 13. This showed that 25% substitution of live micro-algae with DT is possible without affecting growth of P. margaritifera larvae of less than 150 µm SL. There was no significant difference in survival of P.margaritifera larvae fed 100% LA, 75% LA +25% DT and 50% LA + 50% DT over a period of 13 days. Highest survival (43.7%) occurred in larvae fed 100% DT while lowest (approximately 18%) occurred in controls (50% live micro-algae and unfed) during the first experiment. The result of the second experiment indicated that with increasing size, larvae are capable of accepting a higher proportion of dried Tetraselmis in their diet. There were no significant differences in larval growth or survival, between treatments where LA was partially and completely substituted diets with DT.