Marbled crayfish

Marbled crayfish are the only known decapod crustaceans to reproduce only by parthenogenesis.[5] All individuals are female, and the offspring are genetically identical to the parent.[8][9] Marbled crayfish are triploid animals[8][10] with 276 chromosomes,[11] which may be the main reason for their parthenogenetic reproduction. It is hypothesized that marbled crayfish originated from an error in meiosis resulting in a diploid gamete, which was then fertilized and created a viable triploid individual in a single generation.[8][12] Marbled crayfish are thus a model for the rapid generation of species.[8] Unlike other parthenogenetic organisms, the marbled crayfish is a relatively young species.[11]

Because marbled crayfish are genetically identical, easy to care for,[13] and reproduce at high rates, they are a potential model organism, particularly for studying development.[14] A major drawback, however, is the long generation time (several months) compared to other research organisms.[15]

The marbled crayfish genome was sequenced in 2018, which provides an essential foundation for further research.[12]

Marbled crayfish have caused concern as a potential invasive species[5] because only a single individual is needed to establish a new population, and they can reproduce at high rates. Marbled crayfish are also a known carrier of a crayfish plague pathogen, Aphanomyces astaci.[16] Marbled crayfish inhabit freshwater environments, and have not successfully invaded ecosystems with higher salinity levels due to their reduced ability to reproduce and grow. [17] However, it has been proven that they can adjust to increasing saline environments, which may allow for their further expansion.[17]

They have since been introduced into natural ecosystems on four continents. They have been found in the wild in the following countries:

While initial reports of marbled crayfish in the wild in Europe consisted of only single individuals,[24] the number of European countries reporting populations of marbled crayfish is rising.[38]

The Madagascar population has grown rapidly[30][12] and is estimated to be in the millions, with their geographical distribution having increased 100-fold from 2007-2017,[11] causing concern among local authorities.[39]

Marbled crayfish are one of the most widely distributed species of crayfish in the international pet trade[40][41][42] and release from aquariums has likely been the main source of unwanted introductions. Concerns about the potential damage from their introduction have prompted several jurisdictions to regulate ownership of marbled crayfish.

The European Union instituted "a total ban on the possession, trade, transport, production and release of these species [including the marbled crayfish] in the wild" in 2016.[43][44][45][46]

Japan banned most North American crayfish species, including marbled crayfish, in 2020.[47]

Marbled crayfish are prohibited in the American states of Idaho,[48] Missouri,[49] Tennessee,[50][51] and Michigan,[52][53] Maryland,[54] and the Canadian province of Saskatchewan.[55]

Wikimedia Commons has media related to Procambarus fallax forma virginalis and Unidentified Procambarus.

• Marmorkrebs.org
• "Procambarus fallax f. virginalis (Marmorkrebs)". Invasive Species Compendium. CAB International.