Regulation of Tissue Growth in Crustacean Larvae by Feeding Regime

Growth of the posterior dorsal carapace, the underlying epidermal cells, and the lateral thoraco-abdominal muscle was examined in the second instar Palaemonetes pugio under different feeding regimes. Control larvae (continuous feeding) and larvae fed for the first two days of the molt cycle demonstrated a mean molt increment (MI) of 10.6 and 11.1%, respectively. The muscle in these control larvae grew in width by 6.7%. Starved second instar larvae showed a MI of 3.2% and an increase in muscle width of 1.3%. Larvae fed on only one day of the molt cycle had MIs of 5.5-6.6%--values significantly different from that of the control larvae. Muscle growth in partially fed larvae was intermediate (3.9-4.5%) between those of fed and starved larvae. The increase in the density of the epidermal cells was proportional to the MI for the control and starved larvae, and for larvae fed on day 2; larvae fed only on day 1 or day 3 grew less or more, respectively, than the MI predicted from the increase in cell density. The results show that nutritional state is a strong regulator of tissue growth in shrimp larvae.