Crayfish | Crawfis | Huna | Lobster Galery

Engaeus Orramakunna

Tasmania's Freshwater Burrowing Crayfish
Mt. Arthur Burrowing Crayfish
Mount Arthur Burrowing Crayfish
Burrowing Crayfish
E. Orramakunna
Engaeus Orramakunna

Kingdom : Animalia
Phylum : Arthropoda
Subphylum : Crustacea
Class : Malacostraca
Order : Decapoda
Infraorder : Astacidea
Family : Parastacidae
Genus : Engaeus

Species : Engaeus Orramakunna



The Mount Arthur Burrowing Crayfish grows to 8 cm long. It is orange in colour and is paler on its underside and darker on its back. Younger animals may vary from dark reddish-brown to translucent grey-blue in colour (Bryant & Jackson 1999b). The species has long antenna which extend well beyond the edge of the carapace (LEC 2003).

Australian Distribution
The Mount Arthur Burrowing Crayfish is known from a range of 300 km² centred on Mount Arthur in north-east Tasmania. Its occupancy within its range is not well known, however, suitable habitat is common. The species extends to near Lilydale, Nabowla and south Springfield. Its range borders on distributions of other freshwater crayfish, including Engaeus tayatea, E. nulloporius, E. mairener and E. leptorhynchus. The species is also found near Launceston, although its exact boundary remains undefined. The north-east extreme of its distribution extends into an area of significant biological diversity and evolutionary importance for burrowing crayfish and Tasmanian fauna as a whole (Horwitz 1996, cited in Doran 1999b). Approximately 55% of the species' northern distribution occurs in state forests. A comprehensive review of the species distribution can be found in Doran and Richards (1996).

Population Information
The number of adult individuals is estimated to be 1 400 000 to 4 000 000. Since European settlement the species is considered to have undergone a substantial reduction in numbers (60–66%) due to human disturbance (TSSC 2001af).

Habitat
The Mount Arthur Burrowing Crayfish has been found in high abundance in a range of habitats. These include undisturbed rainforests, eucalypt forest, open pasture, cattle trampled pasture and roadside gutters. The primary habitat requirement appears to be a high level of moisture combined with soil suitable for burrowing.

Engaeus Orramakunna distribution

There is no uniform distribution of burrows throughout the species' habitat. In some sites burrows are uniformly distributed, while in others they are patchy (Doran & Richards 1996). Burrows are found in steep sided banks, steep stream slopes and flat marshy seeps and pans. Burrows are commonly found in areas with high canopy cover, high ground cover or low canopy cover and low ground cover and all combinations of these sites. Burrows are recorded in both open and closed habitat. Despite the ad hoc distribution and habitat or burrow location, all active burrows were found in sites of high soil moisture and high clay content (DPIW 2007b). The species occupies burrow types connected to the water table and types independent of the water table, which are dependant on surface runoff (Horwitz & Richardson 1986). In the southern regions of the species' range the soil character changes, becoming darker topsoils with an underlying reddy-grey clay (Doran & Richards 1996).

Burrows are usually found in the presence of ferns such as Dicksonia antarctica. They are also found under a range of canopy species, including eucalypt, tea-tree, paperbarks, Radiata Pine (Pinus radiata) and Sassafras (Atherosperma moschatum) (Doran & Richards 1996). A comprehensive review of the species' habitat can be found in Doran and Richards (1996).

Life Cycle
Burrowing crayfish live their entire lives within burrow systems, only emerging occasionally at night and in damp, overcast conditions. All burrowing crayfish have gills under the carapace, making them dependent on water to breathe (DPIW 2007).
The Mount Arthur Burrowing Crayfish is believed to begin breeding in late May. Females of the species have been found carrying undifferentiated eggs in mid-June, early August, late October and early November. Males have been observed occupying the same burrow as females throughout these periods (Doran 1999b).