Biochemical changes during larval development of the xanthid crab Rhithropanopeus harrisii. I. Protein,total lipid,alkaline phosphatase,and glutamic oxaloacetic transaminase

Protein, total lipid, and the activities of the enzymes alkaline phosphatase (AP) and glutamic oxaloacetic transaminase (GOT) were measured daily during larval development of the xanthid crab Rhithropanopeus harrisii (Gould). Percent increase in fresh weight was greatest on the first day after each molt. Protein and total lipid per larva increased during the second, third, and fourth zoeal stages, with the most marked increase during the third. When calculated as percent fresh weight, marked accumulation of both protein and total lipid occurred during the third zoeal stage. GOT activity remained stable during the third zoeal stage, but increased significantly during the fourth zoeal stage. AP showed a 4-day cycle of activity apparently related to the molt cycle. It is suggested that increased protein and total lipid content during the third zoeal stage indicate nutritional requirements prior to metamorphosis. Biochemical change may be a more relevant indicator of growth during larval development than either size increase or molt frequency when assessing the value of various diets in the culture of crabs.