TISSUE ACCUMULATION AND THE MOLT CYCLE IN JUVENILES OF THE AUSTRALIANFRESH-WATER CRAYFISH CHERAX DESTRUCTOR

1. This paper investigates moult stage and size-specific changes in wh ole body composition during growth in juvenile crayfish in order to be tter describe the nature of growth and energy use. 2. Composition is d escribed in terms of moult stage and size-specific wet, dry and ash-fr ee dry weight, water, carbon, protein nitrogen, non-protein nitrogen, ash and energy. Dry weight and ash-free dry weight (AFDW) peaked in th e middle and in the later stages of premoult. Both peaks were about 2- 2.3 times postmoult weight. Losses in tissue weight during ecdysis wer e substantial in the smallest crayfish but declined with size. Water w as taken up between late premoult and early postmoult. Tissue accumula tion occurred primarily between B and D-1.3, With further weight gain largely the result of fluid uptake. Ash increased immediately postmoul t with a major peak occurring during intermoult. Mean organic carbon v aried between 33 and 35.5% of the body and 49% of the exuvia. Chitin v aried between 9 and 17% of body AFDW and made up about 50.5% of the ex uvia. Protein content varied between 47 and 62% of body AFDW and about 25% of the exuvia. Carbon, chitin and protein were not affected by mo ult stage but protein declined with ocular carapace length (OCL) in la rger crayfish. Mean caloric content varied between 19 and 22 J mg(-1) AFDW depending on size and moult stage. Caloric content increased with OCL during premoult and early intermoult then declined with size unti l part of the way through premoult. 3. Relationships between protein, chitin and remaining carbon (organic carbon minus chitin) were examine d. It is suggested that protein and some carbon are catabolized during the moulting process, possibly to fuel metabolism. Models are present ed showing changes in proximate composition over the moult cycle for t wo sizes of crayfish, and tissue and energy accumulation and loss over a series of moult cycles and sizes from 3.1 mm to 17 mm OCL.