Marmorkrebs, or marbled crayfish, are parthenogenetic crayfish that were discovered in the pet trade in Germany in the 1990s.^[2] Marmorkrebs are closely related to the "slough crayfish", Procambarus fallax.^[3] Procambarus fallax is widely distributed across Florida,^[4] but there are no known natural populations of Marmorkrebs. Information provided by one of the original pet traders as to where they got Marmorkrebs was deemed "totally confusing and unreliable".^[5]

Model organism

Marmorkrebs are the only known decapod crustaceans to reproduce by parthenogenesis.^[2] All individuals are female, and the offspring are genetically identical to the parent.^[6] Because Marmorkrebs are genetically identical, easy to care for,^[7] and reproduce at high rates, they are a potential model organism, particularly for studying development.^[8] A major drawback, however, is the long generation time (several months) compared to other research organisms.^[9]

Invasive species

Marmorkrebs have caused concern as a potential invasive species^[2] because only a single individual is needed to establish a new population, and they can reproduce at high rates. They have since been introduced into natural ecosystems on three continents. They have been found in the wild in Germany,^[5][10][11] Italy,^[12] The Netherlands,^[13] Madagascar,^[14] and Japan,^[15] probably through release or escape from aquaria.

Although most reports of Marmorkrebs in the wild in Europe have consisted of only single individuals,^[10] an established population has now been documented in Germany,^[11] with reports of a second population in another German locale.^[16]

The Madagascar population is growing rapidly,^[14] causing concern among local authorities.^[17]

Although there are no confirmed cases of Marmorkrebs being found in the wild in North America, they are widely distributed among hobbyists in the North American pet trade.^[18] Due to concerns about the possible damage caused by the introduction of Marmorkrebs, Missouri added them to its prohibited species list.^[19]

References

Procambarus is a genus of crayfish in the family Cambaridae, all native to North and Central America. It includes a number of troglobitic species, and the parthenogenetic Marmorkrebs. Originally described as a subgenus for four species, it now contains 160 species in 16 subgenera.

Biogeography

The majority of the diversity is found in the south-eastern United States, but the genus extends as far south as Belize and Guatemala, and as far east as Cuba.^[2] Subgenus Ortmannicus' is the most widespread, with the range of Procambarus acutus extending as far north as the Great Lakes and New England, as well as south into north-eastern Mexico; the subgenus Girardella also extends from the Great Lakes to Mexico, but is distributed further west than Ortmannicus.^[3] Scapulicambarus and Pennides are widespread in the southeastern United States, where Remoticambarus also lives, further west (Texas and Louisiana) than Leconticambarus which is centred on Florida and neighbouring states. The subgenus Austrocambarus has the most southerly distribution, being found in Cuba and parts of Central America from Mexico to Belize. The other subgenera are more restricted in their distributions, including three endemic to central Mexico, and six endemic to small areas in the United States.^[2][3]

Many species of Procambarus have been introduced to other continents, where they are frequently categorized as invasive species.^[4][5]

Description

Procambarus can be distinguished from other genera of crayfish by the form of the first pleopod in males, which typically has three or more processes at the tip, compared to two or fewer in Orconectes and Cambarus.^[6]

Ecology

A number of Procambarus species are troglobitic, living in caves, particularly in karstic areas. These include both species in subgenus Lonnbergius (Procambarus acherontis and Procambarus morrisi) and the single species in the subgenus Remoticambarus, Procambarus pecki.^[7]

Taxonomy

Procambarus was originally described by Arnold Edward Ortmann in 1905 as a subgenus of a wider genus Cambarus, and originally contained only four species (Procambarus williamsoni, Procambraus diguieti, Procambraus mexicanus and Procambraus cubensis).^[8] The subgenus was elevated in 1942 to the taxonomic rank of genus by Horton H. Hobbs, Jr., who later erected most of the subgenera now recognised within the genus, in his 1972 monograph The subgenera of the crayfish genus Procambarus (Decapoda: Astacidae).^[3]

Subgenera and species

References

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