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Cherax

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Cherax
Cherax destructor
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: Malacostraca
Order: Decapoda
Suborder: Pleocyemata
Family: Parastacidae
Genus: Cherax
Erichson, 1846
Type species
Astacus preissii
Erichson, 1846

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. Together with Euastacus, it is also the largest crayfish genus in the Southern Hemisphere.

Habitat

Members of the cherax genus can be found in lakes, rivers, and streams across most of Australia and New Guinea.[1]

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.[2] New Guinea is also home to the only known cave-living crayfish in the Southern Hemisphere, C. acherontis.[3]

Introduced

Some species are very colourful and sometimes seen in the freshwater aquarium trade.[4]

Reproduction

[clarification needed]

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.[5]

Yabbies can inhabit shallow creeks during the wet season and burying themselves during droughts

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.[6]

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 they will produce viable offspring.[7] During the fight, both release urine. The female's release of urine triggers a sexual response from the male.[7] The male's release of urine is an aggressive response towards the fight with the female. When the male smells the female's urine, it will stop releasing its own, hoping the female will allow them to copulate.[citation needed]

Once the female allows it, the male will position itself on its back, and deposit its sperm.[8] Unlike other crayfish species, the 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.[9]

Female C. dispar uses honest signalling of strength, meaning the size of their chelae is a good indication to other C. dispar about that individual's strength.[9] Individuals possessing larger chelae engage in more agonistic encounters and are also more likely to win.[9] 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.[9]

Species

Cherax "Blue Moon" which could be C. boesemani or C. holthuisi

The genus contains at least 59 species:[10][11]

References

  1. ^ Munasinghe, D. H. N.; Burridge, C. P. & Austin, C. M. (2004). "The systematics of freshwater crayfish of the genus Cherax Erichson (Decapoda: Parastacidae) in eastern Australia re-examined using nucleotide sequences from 12S rRNA and 16S rRNA genes" (PDF). Invertebrate Systematics. 18 (2): 215–225. doi:10.1071/IS03012 – via ResearchGate.
  2. ^ Polhemus, Dan A.; Englund, Ronald A. & Allen, Gerald R. (2004). Freshwater Biotas of New Guinea and Nearby Islands: Analysis of Endemism (PDF) (Report). Bernice Pauahi Bishop Museum, Conservation International.
  3. ^ a b Patoka, Jiří; Bláha, Martin; Kouba, Antonín (2017). "Cherax acherontis (Decapoda: Parastacidae), the first cave crayfish from the Southern Hemisphere (Papua Province, Indonesia)". Zootaxa. 4363 (1): 137–144. doi:10.11646/zootaxa.4363.1.7. PMID 29245414.
  4. ^ a b Blaszczak-Boxe, Agata (13 May 2015). "Mysterious beautiful blue crayfish is new species from Indonesia". New Scientist. No. 3021. Retrieved 28 May 2015.
  5. ^ "Crayfish". www.dept.psu.edu. Archived from the original on 18 July 2022. Retrieved 27 May 2022.
  6. ^ Aquiloni, L. & Gherardi, F. (2008). "Mutual mate choice in crayfish: Large body size is selected by both sexes, virginity by males only". Journal of Zoology. 274 (2): 171–179. doi:10.1111/j.1469-7998.2007.00370.x. hdl:2158/252681. S2CID 84513148.
  7. ^ a b Berry, Fiona C. & Breithaupt, Thomas (2010). "To signal or not to signal? Chemical communication by urine-borne signals mirrors sexual conflict in crayfish". BMC Biology. 8 (1): 25. doi:10.1186/1741-7007-8-25. PMC 2867775. PMID 20353555.
  8. ^ Barki, Assaf & Karplus, Ilan (1999). "Mating Behavior and a Behavioral Assay for Female Receptivity in the Red-claw Crayfish Cherax quadricarinatus". Journal of Crustacean Biology. 19 (3): 493–497. doi:10.2307/1549258. JSTOR 1549258.
  9. ^ a b c d Bywater, C. L.; Angilletta, M. J. & Wilson, R. S. (2008). "Weapon Size Is a Reliable Indicator of Strength and Social Dominance in Female Slender Crayfish (Cherax dispar)". Functional Ecology. 22 (2): 311–316. doi:10.1111/j.1365-2435.2008.01379.x.
  10. ^ Fetzner, James W. Jr. (11 January 2010). "Genus Cherax Erichson, 1846". Crayfish Taxon Browser. Carnegie Museum of Natural History. Archived from the original on 2 April 2015. Retrieved 24 November 2015.
  11. ^ "Cherax". Integrated Taxonomic Information System.
  12. ^ Patoka, Jiří; Bláha, Martin & Kouba, Antonín (2015). "Cherax (Astaconephrops) gherardii, a new crayfish (Decapoda: Parastacidae) from West Papua, Indonesia". Zootaxa. 3964 (5): 526–536. doi:10.11646/zootaxa.3964.5.2. PMID 26249463.
  13. ^ a b Patoka, Jiří; Bláha, Martin & Kouba, Antonín (2015). "Cherax (Cherax) subterigneus, a new crayfish (Decapoda: Parastacidae) from West Papua, Indonesia". Journal of Crustacean Biology. 35 (6): 830–838. doi:10.1163/1937240x-00002377.
  14. ^ Dockterman, Eliana (25 August 2015). "New species of crayfish named after Edward Snowden". Time. Retrieved 25 August 2015.
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