Life history of Parastacoides tasmanicus tasmanicus Clark, a burrowing freshwater crayfish from south-western Tasmania

Abstract

The life history of the semi-terrestrial burrowing freshwater crayfish Parastacoides tasmanicus tasmanicus was studied in the wet heathlands of south-western Tasmania. Data on seasonal reproduction, fecundity and growth were obtained from regular monthly sampling over a period of two years. The development of gonads, size at maturity, sexual dimorphism and reproductive condition were determined by detailed examination of changes in reproductive morphology and gonad condition. P. t, tasmanicus attains maturity at a relatively late age (3-5 years) and large size (25-30 mm carapace length) and has a long life span (< 10 years) and a slow and variable growth rate. The growth rate appears to be a function of cold water temperature and low-nutrient diets. Males reach sexual maturity at a smaller size than do females. Mating and spawning, which closely follow the female moult, occur in early autumn when males and reproductive females pair within their burrow systems; eggs are carried over winter and hatch early the following summer, and young remain attached to their mothers until mid summer. Mature females appear to exhibit a biennial moulting and breeding cycle, an apparently unique strategy among parastacid crayfish, which is probably a result of the cooler climate conditions in Tasmania.