Changes in the physiology and chitin metabolism in cultured juvenile Panulirus ornatus across the moult cycle

Abstract

Crustaceans undergo periodic moulting events to facilitate growth, this is a physiological and energetically demanding process. In an aquaculture environment, crustaceans are generally cultured in a defined space and often at high densities, where exposure to cannibalism may be greater than in the wild. Panulirus ornatus is one such emerging aquaculture candidates, moulting frequently as juveniles and providing the opportunity to investigate the relationship between physiology and genetics throughout this important developmental period. In this study, P. ornatus juveniles were assessed every three days across the seventh to eighth juvenile moult phase, sampling was divided into six distinct time points. Brix index, hepatosomatic index, and circulating ecdysone concentrations were measured across these time points. The Brix index was validated as a useful tool for assessing the moult-stages of juvenile P. ornatus, with an increase in Brix value seen in the lead up to ecdysis. Chitin metabolism was mapped, with Chitinase 3 demonstrating hepatopancreas specificity, indicating a role outside of breakdown of dietary chitin. The investigation of physiological parameters across a moult cycle provides a basis for improving moult cycle staging in cultured P. ornatus juveniles and provides further characterisation of the changes that occur during moulting in this species.