The marbled crayfish or Marmorkrebs, is a parthenogenetic crayfish that was discovered in the pet trade in Germany in the 1990s. Marbled crayfish are closely related to the "slough crayfish", Procambarus fallax, which is widely distributed across Florida. No natural populations of marbled crayfish are known. Information provided by one of the original pet traders as to where the marbled crayfish originated was deemed "totally confusing and unreliable". The informal name Marmorkrebs is German for "marbled crayfish".
Model organism
Marbled crayfish are the only known decapod crustaceans to reproduce only by parthenogenesis. All individuals are female, and the offspring are geneticallyidentical to the parent. Marbled crayfish are triploid animals, 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. Marbled crayfish are thus a model for the rapid generation of species. Because marbled crayfish are genetically identical, easy to care for, and reproduce at high rates, they are a potential model organism, particularly for studying development. A major drawback, however, is the long generation time compared to other research organisms. In 2018 the genome was sequenced, which provides an essential foundation for further research.
Invasive species
Marbled crayfish have caused concern as a potential invasive species 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 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, the number of European countries reporting populations of marbled crayfish is rising. The Madagascar population has grown rapidly, causing concern among local authorities.
Regulation
Marbled crayfish are one of the most widely distributed species of crayfish in the international pet trade 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 in the wild". Marbled crayfish are prohibited in the American states of Idaho, Missouri, Tennessee, and Michigan, and the Canadian province of Saskatchewan.
