Crayfish - The Australian Museum

What are Crayfish?

Crayfish belong to a group of animals called Crustaceans and are part of the phylum Arthropoda. Other Arthropods are insects (Insecta), spiders (Arachnida), and centipedes and millipedes (Myriapoda). All Arthropods have a hardened outer shell, called cuticle (made from calcium carbonate) that acts as a skeleton.

Crustaceans are distinguished from the other arthropods by their two pair of antennae - an outer pair called antennae, and an inner pair called antennules. Crayfish bodies are divided into three parts; the head, the thorax (the section that contains the legs), and the abdomen (or the tail, which is the edible part of many large crustaceans including crayfish, prawns and lobsters).

Crayfish, like many crustacean have a carapace or shield which projects backwards from the head and covers all of the thorax The carapace has two functions; firstly it protects the delicate feather-like gills which branch off from the base of the legs, and secondly it provides a water channel that is a constant flow of oxygenated water to pass over the gills and enables the crayfish to breathe.

Family Heritage and the Relatives

All freshwater crayfish in Australia belong to the Family Parastacidae.

Australia's crayfish fauna are divided into nine genera (or groups of species) which include over 100 species. The three most common and widespread genera are Cherax, Euastacus and Astacopsis. These are all medium to large crayfish that are found in streams, lakes and swamps. Cherax species are the best known crayfish and occur over the widest range, from northern, eastern and south-western Australia and are distinguished by having smooth bodies and claws. Cherax are also the main species used in the rapidly growing aquaculture industry.

They have a relatively rapid rate of growth and greater tolerances of larger temperature ranges and water conditions than many other crayfish. The three main species used in yabby farming and found in pet shops in Australia are the Dam Yabby Cherax destructor, the Marron Cherax tenuimanus from Western Australia, and the Queensland Red Claw Cherax quadricarinatus.

The Yabby

The yabby (Cherax destructor) has the largest range of all Australian crayfish. It occurs across most of Victoria, western New South Wales, south-western Queensland and eastern South Australia. They are probably the most hardy crayfish. They can tolerate poor water conditions and long periods of drought by burrowing deep into the river bed or dam wall in order to stay moist. This species was named destructor because of the damage its burrowing caused in dam walls and levee banks. Yabbies range in colour from brown, green to pale blue with mottled claws.

The Queensland Red Claw is characterised, as its name suggests, by a bright red patch on the outside of the large claw. The Marron is a dark brown or black or sometimes a bright blue colour. The striking blue form of the Marron is being selectively bred and are becoming increasingly popular as pets.