Biochemical composition of embryonic blue crabs Callinectes sapidus Rathbun 1896 (Crustacea : Decapoda) from the Gulf of Mexico
Blue crab Callinectes sapidus embryos from the Mississippi Sound were sampled in spring and in late summer to determine patterns of biochemical composition and of yolk utilization during embryogenesis and to ascertain potential seasonal differences in biochemical composition. The diameter of spring embryos was similar to6% greater than summer embryos but this significant size difference was due to increased water content, not to increased organic content. The general trend in initial biochemical composition was similar in both seasons; protein was the primary component at similar to50% of initial dry weight followed by lipid (similar to30%), ash (similar to8%) and carbohydrate (6%). The general trend for utilization of organic reserves during embryogenesis was also similar seasonally. Lipid was the primary component metabolized during embryogenesis (44-48% of initial stores were utilized) followed by protein (13-16% utilized) and carbohydrate (similar to13% utilized). Calculated on a dry weight basis, spring embryos had significantly lower lipid but significantly higher ash than summer embryos; there were no significant seasonal differences in protein or carbohydrate. Caloric expenditure on a dry weight basis was significantly different seasonally. There appear to be geographic differences among blue crabs; our results differ from those of a previous study of blue crab embryos from North Carolina waters.