Changes in the chemical composition of the common shore crab,Carcinus maenas, during the molting cycle

Summary

Juvenile and young adult specimens ofCarcinus maenas were kept in the laboratory under controlled conditions. The main organic constituents and their variations during the molt cycle were quantitatively determined.

• 1. During postmolt the chitin concentration rises rapidly (20–74 mg/g dry weight) in parallel to the dry weight (120–293 mg/g fresh weight). Both decrease again before ecdysis (Fig. 1).

• 2. The glycose level in the hemolymph (50–80 μg/ml) shows no significant variation during the molt cycle (Fig. 2).

• 3. The glycogen concentrations in integument, (14–180 mg/g dry weight), gills (5.5–66 mg/g dry weight), muscle (8.8–41 mg/g dry weight), heart (135–308 mg/g dry weight) and hemolymph (160–690 μg/ml) reach their maximum values during the premolt stage. The highest glycogen content in the midgut gland (83 mg/g dry weight) is observed immediately before and after ecdysis. Glycogen storage in heart and hemolymph, can, account for about half of the glycogen stored in the midgut gland (Figs. 3,4 and 5).

• 4. The lipid concentration in the hemolymph (120–440 μg/ml) and in gills (33.6–70 mg/g dry weight) rises during the premolt stage (Figs. 6 and 7).

• 5. The protein concentration in the hemolymph increased during premolt (9–31 mg/ml). The copper content (13–42 μg/ml) varies in parallel to the protein concentration indicating that the proportion of hemocyanin to total proteins remains constant during the molting cycle (Fig. 8).