Some changes in biochemical composition with season and during the moulting cycle of the common shore crab, Carcinus maenas (L.)

Abstract

Changes in the size and biochemical composition (glycogen, total carbohydrate, neutral fat, phospholipids, protein and non-protein nitrogen) have been followed throughout the year in the ovary and both male and female hepatopancreas of Carcinus maenas. Changes in size and biochemical composition of the hepatopancreas of Carcinus have also been examined throughout the moulting cycle. There are no clearly defined seasonal changes in either size or composition of the hepatopancreas; there is, however, a decrease in neutral fat levels in late autumn and winter in both sexes which may be due to decreased feeding at this time, and a second fall in late spring which may be caused by the recruitment to the population of previously berried and non-feeding females and recently moulted males. Carcinus appears to store less material before the moult than does Cancer and some animals appear to moult without having accumulated any appreciable reserves. In the summer, when the moulting cycle of Carcinus is characterized by ecdysis, the glycogen stores in crabs in stages C 4 and D 1 are larger than in the winter. Small, actively moulting premoult crabs when fed in captivity accumulate very large stores of glycogen in the hepatopancreas while larger, intermoult crabs in anecdysis store very little. On starvation the reserves of glycogen (and other carbohydrate material), neutral fat, and non-protein nitrogen decrease: in contrast, protein nitrogen remains constant, while phospholipid rises. On re-feeding such starved crabs on mussels the store of total carbohydrate is again rapidly established, glycogen and non-protein nitrogen fairly rapidly, and neutral fat only slowly.