DEPLETION OF NUTRIENT RESERVES DURING EMBRYOGENESIS IN THE SCALLOP PATINOPECTEN-YESSOENSIS (JAY)

The levels of biochemical components and energy in spawned eggs of Patinopecten yessoensis (Jay) were higher and more consistent than those for other bivalve eggs which are cited in the literature. During embryogenesis, linear deposition of 0 to 40.5% dry wt of shell was the principal biochemical change. The energy calculated for shell deposition, 18.8 kJ.g-1, accounted for 74.4% of total energy depleted in the egg. Lipid, carbohydrate and protein were catabolized simultaneously and linearly with time of embryonic development. Total energy expended during development, 10.2 kJ.g-1, was derived 47.6% from lipid, 7.5% from carbohydrate and 44.9% from protein. Glucose was depleted linearly as the dominant source of carbohydrate energy in the egg. The RNA-DNA ratio, indicating rate of protein synthesis, declined exponentially from 11.98 in ther fertilized egg to 1.91 in the D-larva. The combined saturated and mono-ethylenic fatty acids increased linearly with embryogenesis and the polyunsaturated fatty acids declined, principally in the linolenic family of acids. Eicosapentaenoic and docosahexaenoic acids exhibited, respectively, an energy and structural role during embryonic development. Protein and lipid were equally important as sources of energy during embryonic development of P. yessoensis.