Marbled Crayfish

The marbled crayfish is the only known parthenogenetic (asexually reproducing) decapod crustacean. All individuals are female and lay eggs without fertilization; the offspring are genetic copies of the mother. It was first noticed in the aquarium trade in Germany in the 1990s and was described as a separate species in 2017. It is named after the dark marbled pattern on its brown-olive body.

Legal and ethical warning: The marbled crayfish is on the European Union's list of invasive alien species; keeping, breeding, selling and transporting it are banned in the EU. Individuals that escaped or were released from aquariums have established large invasive populations in many lakes in Europe and in Madagascar. Check the current regulations for its legal status in Türkiye. Never release it into the wild. If you have some, find out the legal status before giving them to anyone else and limit their reproduction.

It has no natural habitat; the species arose in the aquarium. Where it has got into the wild, it spreads rapidly through a wide range of fresh waters, including lakes, canals, rice paddies and swamps.

• Volume: 60 liters or more for a single individual.
• Hiding places: Sturdy caves; it hides after molting.
• Lid: A lid without gaps is essential; even a single escaped individual can found a new population on its own.
• Water: 20–25°C, moderately hard to hard, alkaline water; it tolerates a wide range of parameters.
• Waste water: Never pour aquarium water, bottom mulm or filter sponges into a stream or lake; eggs and young can spread this way.

Omnivorous and greedy. It is given crayfish tablets, granules, blanched vegetables, dried leaves and occasionally animal protein (bloodworms, shrimp).

Somewhat less aggressive than other crayfish, but it still catches bottom-dwelling and slow fish, shrimp and snails; it cuts and eats plants.

Good companions: It should be kept alone.

Avoid: Fish, shrimp, snails, live plants and other crayfish.

A single individual can produce hundreds of young within a few months; that is why a "colony" forms on its own and uncontrollably. In a crowded aquarium individuals eat each other and water quality deteriorates rapidly. Keeping reproduction under control is the most important care issue with this species.

No male is needed. Every mature female carries hundreds of unfertilized eggs under her tail every few months. There is no larval stage; the young hatch as fully formed little crayfish and soon breed themselves.

• Failed molts: Calcium deficiency or sudden changes in parameters.
• Crayfish plague: Like crayfish of North American origin, it can carry this disease; it is deadly to native crayfish.
• Overcrowding: Rising ammonia and cannibalism.

There are no males; all individuals are female.