Compositional changes in the larva to juvenile development of the scallop Crassadoma gigantea (Gray)

Abstract

An assessment of the biochemical composition of mature, immature and starved larvae, and post-metamorphic juveniles of the rock scallop, Crassadoma gigantea (Gray), provided information on the accumulation and expenditure of energy during scallop development, and an explanation for high mortality in post-metamorphic juveniles. Neutral lipid was the major reserve accumulated in maturing larvae of C. gigantea, and more precisely reflected the nutritional conditions of the larvae than either protein or carbohydrate. Total energy in pre-metamorphic larvae declined with increasing age at maturity. A 26.6% energy loss from pre-metamorphic larvae during 4 days of starvation was derived from linear catabolism of 46.7% lipid and 7.8% carbohydrate, and curvilinear catabolism of 45.5% protein. Catabolism of lipid, carbohydrate and protein accounted for 59.9%, 1.6% and 38.5%, respectively, of the 58.3% total energy loss from the transition of pre-metamorphic larvae to juveniles 25 days after settlement. Fatty acids profiles of pre- and post-metamorphic scallops indicated that early post-metamorphic juveniles assimilated food, but at a rate insufficient to meet the demands for instinctive shell deposition and growth. Continued reliance on endogenous reserves for post-metamorphic survival emphasizes the crucial need for energy sufficient pre-metamorphic larvae. A comparison with other bivalve studies suggests that the mobilization of endogenous reserves appears to be a function of the availability of the reserves stored preferentially by different species of bivalves.