|
| Parastacidae |
| Major Group: Crustacea Minor Group: Malacostraca Order: Decapoda Family: Parastacidae Cherax destructor, Cherax tenuimanus and Cherax quadricarinatus are commonly collected and farmed for human consumption and fish bait both domestically and in aquaculture and food trades. |
||
|
||
|
|
||
|
||
|
|
||
|
||
| Ecology: Instream habitat: Parastacidae species inhabit a variety of permanent and ephemeral lotic and lentic waters including creeks, streams, rivers, small tributaries, drainage channels, roadside gutters and seepages, swamps, pools, lagoons, ponds and billabongs. The type and location of waters inhabited ranges from acidic swamps and rainforest streams to more alkaline coastal streams and floodplain country very close to the sea, from heathlands and forested areas to cleared pastures, from near sea level to alpine high country. Engaeus species have also been found in interstitial waters, a cave and at the base of small trees where roots create water pockets. Crayfish and yabbies are found under stones and rotting logs or amongst sedges and leaf litter in sheltered littoral areas on rock, sand, clay or loamy substrata as well as in deeper water. Feeding ecology: Crayfish and yabbies may be opportunistic feeders and predators but are generally detritivores. There are three types of feeding behaviour. 1) Browsing, gathering and ingesting detritus or other edible materials as they are encountered. 2) Hunting, premeditated stalking and rapid capture of live prey e.g. fish, tadpoles, frogs, utilizing claws or first pairs of pereiopod. 3) ‘Bulldozing’; (esp. when food supply is low) by pressing anterior cephalothorax into the substratum whilst piling material over the buried mouth with first pairs of walking legs, then ‘doze’ along, pushing with last two pairs of pereiopods. Feeding reduces during colder months when growth is very slow. Feeding stops when ecdysis is imminent and recommences some days later when the new shell has hardened. Habit:Crayfish and yabbies may be either nocturnal or diurnal. Gramastacus is free swimming whilst all other genera are burrowing crayfish. The burrows are found in or connected to open waters or the water table. If the waters dry out, the burrows are sealed with a mud chimney. Engaeus and Euastacus species construct extensive burrow systems in soft stream banks, whereas Cherax species construct short burrows preferably in steep banks. Life history: Breeding is seasonal and dependent upon water temperature. Sexual dimorphism can occur in some species. Eggs are large with larvae hatching as miniature versions of the adult. In Cherax destructor summer egg incubation takes three weeks. The young remain with the female for two to three weeks, after third moult (third larval stage) they become independent juveniles in the crayfish population. The first two larval stages are non mobile and non feeding. Moulting takes a few minutes in Cherax destructor but Euastacus armatus takes over an hour. Onset of moulting (premoult) is indicated by the formation of gastroliths (a small calcareous structure which develops on each side of the stomach). During the moult the animal swells by absorbing water. Recently moulted individuals (postmoult) are lighter in colour and lethargic with a softer shell. The empty shell is eaten within a few days to recycle the mineral salts, when shell has hardened (intermoult). The length of the intermoult period varies between species and age groups. Juveniles moult every ten days, young adults four to five times per year and older adults once or twice per year. |
||
| Information Sources: Hansen & Richardson 2006, Davie 2002a, Merrick 1993, Ingram et al 1997, Schultz et al 2007* | ||
More ››› key to genera 
|
||
