Freshwater crayfish, yabbies, marron

Code OV019999

Decapod crustaceans with a prominent rostrum and a tail fan. The abdomen is disproportionately small in some species. Eyes on stalks. A carapace completely covers the dorsal and lateral thorax. The first pair of legs (chelipeds) are particularly robust and terminate in strong pincers (chelae). The largest Australian parastacids can attain a weight of 3.6 kg and length 40 cms, the smallest species weigh only a few grams and are about 2.5 cms long.

Parastacidae can be distinguished from Atyidae (shrimps) and Palaemonidae (prawns) by their robust chelipeds. In addition, unlike in Palaemonidae the third pair of pereopods bear chelae, and unlike in Atyidae the rostrum is somewhat dorsoventrally compressed. Non-decapod shrimp-like animals differ as well in not having the prominent carapace, , except that the cave microshrimp Thermosbaenecea (1 species, 1-1.5mm total length, known from a single cave in WA) has a carapace joined to the head but leaving the thorax free.

Parastacidae occur in many types of water but mostly in small creeks and in lowland still-waters such as ponds, dams and lakes. Not all are totally aquatic, and some prefer seepages or even damp ground such as lawns. The aquatic species tend to travel from one waterbody to another and may protect themselves from unfavourable conditions by burrowing. This may damage dams, banks, etc.

The Australian species belong to the genera Cherax, Euastacus, Astacopsis, Geocharax, Gramastacus, Engaewa, Engaeus, Tenuibranchiurus and Parastacoides. Keys to the genera and species are provided by Horwitz and Austen (1995).

References:

Horwitz, P. and Austen, C.M. (1995) A preliminary key to the species of Australian freshwater crayfish. In: Horwitz, P. (ed.) A Preliminary Key to the species of Decapoda (Crustacea: Malacostraca) found in Australian Inland Waters. Co-operative Research Centre for Freshwater Ecology Identification Guide No. 5., Albury, NSW.