Cherax, commonly known as yabby/yabbies in Australia, is the most widespread genus of fully aquatic crayfish in the Southern Hemisphere. Various species of cherax may be found in both still and flowing bodies of freshwater across most of Australia and New Guinea.

Habitat Members of the Cherax genus can be found in lakes, rivers, and streams across most of Australia and New Guinea. Together with Euastacus, it is also the largest crayfish genus in the Southern Hemisphere.

The most common and widely distributed species in Australia is the common yabby (C. destructor). It is generally found in lowland rivers and streams, lakes, swamps, and impoundments at low to medium altitude, largely within the Murray–Darling Basin. Common yabbies are found in many ephemeral waterways, and can survive dry conditions for long periods of time (at least several years) by aestivating (lying dormant) in burrows sunk deep into muddy creek and swamp beds.

In New Guinea, Cherax crayfish are found widely in rivers, streams, and lakes, with a particularly high diversity in the Paniai Lakes. New Guinea is also home to the only known cave-living crayfish in the Southern Hemisphere, C. acherontis.

Some species are very colourful and sometimes seen in the freshwater aquarium trade. A new species, coloured bright blue, was found in streams in West Papua after being discovered via the aquarium trade in Australia around 2015, and was named Cherax pulcher, pulcher meaning "beautiful".

Reproduction

The mating season for Cherax is during early spring. After fertilisation, eggs develop inside the mother's body for 4 to 6 weeks. After that period, the eggs transition to the outside of the mother's body and rest on the female's tail. Then the eggs continue to develop and hatch in spring.

Both sexes of Cherax are selective with copulation partners. Females tend to choose males with a larger central mass (abdomen and tail) and cheliped. Males tend to select copulation partners who have larger body sizes and are virgins. Opposed to females who were more dominant or had symmetrical chelipeds.

As part of a mating/copulation ritual, males and females fight each other. This allows the female to test the strength of the male to determine if he will produce viable offspring. During the fight, both release urine. The female's release of urine triggers a sexual response from the male. The male's release of urine is an aggressive response towards the fight with the female. When the male smells the female's urine, he will stop releasing his own, hoping the female will allow him to copulate.

Once the female allows it, the male will position himself on her back and deposit his sperm. Unlike other crayfish species, Cherax dispar does not use its cheliped to cage females during copulation. It is mainly used during mating when the males and females fight.

Behaviour In instances when displaying males have chelae of a similar size, they will engage in combat and those with the greater chelae closing force will win.

Female C. dispar use honest signalling of strength, meaning the size of their chelae is a good indication to other C. dispar about that individual's strength. Individuals possessing larger chelae engage in more agonistic encounters and are also more likely to win. In a study of female C. dispar chelae strength, researchers found that chelae size also indirectly indicated the dominance of the female because of its honest indication of strength.

Species

The genus contains at least 60 species:

Cherax acherontis Patoka, Bláha & Kouba, 2017 Cherax albertisii Nobili, 1899 Cherax albidus Clarke, 1936 Cherax alyciae Lukhaup, Eprilurahman & von Rintelen, 2018 Cherax aruanus Roux, 1911 Cherax austini Coughran & Hobson, 2012 Cherax barretti Clark, 1941 Cherax bicarinatus (Gray, 1845) Cherax boesemani Lukhaup & Pekny, 2008 Cherax boschmai Holthuis, 1949 Cherax buitendijkae Holthuis, 1949 Cherax cainii Austin, 2002 Cherax cairnsensis Riek, 1969 Cherax cartalacoolah Short, 1993 Cherax cid Coughran & Furse, 2012 Cherax communis Holthuis, 1949 Cherax crassimanus Riek, 1967 Cherax cuspidatus Riek, 1969 Cherax davisi Clark, 1941 Cherax depressus Riek, 1951 Cherax destructor Clark, 1936 Cherax dispar Riek, 1951 Cherax esculus Riek, 1956 Cherax gherardii Patoka, Bláha & Kouba, 2015 Cherax glaber Riek, 1967 Cherax glabrimanus Riek, 1967 Cherax gladstonensis Riek, 1969 Cherax holthuisi Lukhaup & Pekny, 2006 Cherax leckii Coughran, 2005 Cherax longipes Holthuis, 1949 Cherax lorentzi Roux, 1911 Cherax minor Holthuis, 1996 Cherax misolicus Holthuis, 1949 Cherax monticola Holthuis, 1950 Cherax murido Holthuis, 1949 Cherax neocarinatus Riek, 1967 Cherax neopunctatus Riek, 1969 Cherax nucifraga Short, 1991 Cherax pallidus Holthuis, 1949 Cherax paniaicus Holthuis, 1949 Cherax papuanus Holthuis, 1949 Cherax parvus Short & Davie, 1993 Cherax peknyi Lukhaup & Herbert, 2008 Cherax plebejus (Hess, 1865) Cherax preissii (Erichson, 1846) syn. Cherax angustus McCulloch, 1914 Cherax pulcher Lukhaup, 2015 Cherax punctatus Clark, 1936 Cherax quadricarinatus (von Martens, 1868) Cherax quinquecarinatus (Gray, 1845) Cherax rhynchotus Riek, 1951 Cherax robustus Riek, 1951 Cherax rotundus Clark, 1941 Cherax setosus (Riek, 1951) Cherax snowden Lukhaup, Panteleit & Schrimpf, 2015 syn. Cherax subterigneus Cherax solus Holthuis, 1949 Cherax tenuimanus (Smith, 1912) Cherax urospinosus Riek, 1969 Cherax wagenknechtae /Lukhaup, Eprilurahman 2022 Cherax wasselli Riek, 1969 Cherax woworae Patoka, Akmal, Bláha & Kouba, 2023 Cherax pulverulentus Patoka, Akmal, Bláha, & Kouba, 2025

References