Diet and burrowing habits of the freshwater crayfish, Parastacoides tasmanicus tasmanicus Clark (Decapoda : Parastacidae)

Abstract

Parastacoides tasmanicus tasmanicus, which burrows extensively into the peat soils of south-western Tasmania, is, like most freshwater crayfish, an omnivore. All food categories in the diet vary seasonally. Detritus, including unidentifiable material, is the major food type present in the gut contents, although root and algal material are also important. Less animal material is present in the diet than in the diet of open-water species, and the taxa consumed and size of prey differ between the adults and juveniles. Cannibalism occurred in less than 1% of the crayfish examined, an incidence considerably lower than that reported for any other crayfish species. Animal material was of comparatively little importance, but the low levels of mineral nutrients, bacteria and fungi in peat soils probably increase its importance as a protein source.

The burrows of P. t. tasmanicus include blind, root-lined chambers beneath clumps of sedgeland plants. Larger animals occupy larger burrows and these have a higher proportion of their volume in the form of blind chambers. The animal appears to spend the majority of its time foraging within its burrow system, a behaviour that contrasts with most other crayfish.