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Astacopsis tricornis (Family Parastacidae)

Distribution:

Astacopsis tricornis is endemic to the western half of Tasmania, where it is found in streams, rivers and reservoirs. (TAS).

Features:

Astacopsis tricornis are usually brown on the upper surface with a paler underside, although juveniles can be light brown or almost grey in colour. The rostrum is broad, U-shaped and terminates in more than one spine. Males and females are similar in overall body size, however mature crayfish vary greatly in size, with sexually mature females weighing between 100 grams and one kilogram. Body armature is heavy and Astacopsis species are sometimes referred to as spiny river-dwelling crayfish. Large spines and tubercles occur over most of the animal, particularly on the chelae (claws), carapace and abdomen.

Ecology/Way of Life:

Astacopsis tricornis is found in, or associated with, streams, rivers, and lakes. The animals usually shelter in short burrows in the water or in the stream banks, or under rocks and logs under the water. They are often seen walking in the water, and, despite being aquatic animals breathing through gills, may occasionally be seen walking on the banks of streams. The vegetation surrounding the water-bodies can consist of a variety of types; rainforest, eucalypt forest, and tea-tree shrub. The vegetation supplies most of the food for these animals; they eat semi-decayed wood, leaves, detritus and some animal matter.

In the majority of mainland Australian freshwater crayfish, females bear young every year. However Astacopsis females moult and bear young only every second year. Mating occurs in the autumn. Females usually have less than 100 eggs. The eggs are carried over winter and the young hatch around mid-summer. After hatching, the young stay attached to the female through three moults before becoming independent in the following autumn.

Interaction with Humans/Threats:

A large part of the range of Astacopsis tricornis lies within the boundaries of the Tasmanian World Heritage Area. Therefore the species is relatively well protected, as there has been little human impact within this area. Other areas within its range are subject to clearing through farming, logging and the development of residential communities, however, these do not appear to have a major impact on the crayfish, and they can be found in streams and creeks in highly modified areas. Recently the introduced mainland species Cherax destructor has been found in some watercourses within the range of Astacopsis tricornis; their impact has yet to be determined. Despite their apparent qualities as a food resource, Astacopsis tricornis is not suitable for aquaculture, due to a slow growth rate and preference for cool water.

Other Comments:

Astacopsis tricornis was named by Clark in 1936.

Further Reading:

Hamr, P. (1992). A revision of the Tasmanian freshwater crayfish genus Astacopsis Huxley (Decapoda: Parastacidae. Papers and Proceedings of the Royal Society of Tasmania 126: 91–94.

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

Acknowledgments:

Text and Map by Brita Hansen. Photography by R. Mawbey.

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