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Parastacoides tasmanicus NT (Family Parastacidae)

Distribution:

This species is restricted to the Lake Pedder region of central Tasmania. (TAS).

Features:

This crayfish species is unusual in that it has ten corneous denticles (teeth) on each mandible (jaw); most other species in this genus have only eight.

Ecology/Way of Life:

In common with many species in this genus, this species of freshwater crayfish is found in regions of Tasmania subject to a wide temperature range. Air temperatures in summer can reach the high twenties or thirties, while in winter they can fall below freezing. However, the temperature in the burrows is much more stable, with the maxima below the outside air temperature, and the minima being above the outside air temperature. The burrows therefore provide a refuge for the crayfish from both excessive heat in summer and freezing temperatures in winter. Despite the fact that the crayfish show little in the way of metabolic compensation for the variations in temperature that they encounter throughout the year, they appear to be able to remain active during the coldest periods. They have been known to move about on the surface during frosty weather, and to be active in pools under ice.

The females of this crayfish species moult and produce young only every second year. Mating and spawning occurs between autumn and spring, and females carry the eggs from June to November. Females carry relatively few eggs, usually less than 70. The eggs are relatively large, however, compared with other decapods, and this may be because they are carried over an extended period. The eggs are carried over winter and hatch in early summer, and the young remain attached to the female through two moults. The young are released in late summer and remain within the female's burrow system until her next hatchlings are released.

Interaction with Humans/Threats:

Like the rest of this genus, individuals of this species are relatively slow-growing, and reach a maximum size of only 80 mm. As burrowers, they are not suitable for intensive rearing through aquaculture. Although the range of this species extends into the Tasmanian World Heritage Area, large parts of the range lie outside this reserve.

Other Comments:

Variations within the species yet to be formally described. Refer to Hansen and Richardson (2002).

Further Reading:

Crandall, K.A. & Fetzner, J.W. (2004). Crayfish Home Page. http://crayfish.byu.edu/

Hansen, B., Adams, M., Krasnicki, T. and Richardson, A. M. M. 2001. Substantial allozyme diversity in the freshwater crayfish Parastacoides tasmanicus supports extensive cryptic speciation. Invertebrate Taxonomy 15:667 – 679.

Hansen, B. & Richardson, A.M.M. (2002). Geographic ranges, sympatry and the influence of environmental factors on the distribution of species of an endemic Tasmanian freshwater crayfish. Invertebrate Systematics. 16(4) pp621 – 629.

Acknowledgments:

Text and distribution map by Brita Hansen. Photography by N. Doran.

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