Marmorkrebs

The marbled crayfish is the only known decapod crustacean that reproduces by parthenogenesis, and all specimens are female as a result. Early attempts to identify this species by morphological characters largely failed because most identification keys for Cambaridae (which it was thought to be based on its general appearance) rely strongly on male characteristics. Subsequent genetic studies confirmed that the marbled crayfish belongs to the genus Procambarus and is most closely related to Procambarus alleni and Procambarus fallax (Scholtz et al., 2003; Braband et al., 2006, Souty-Grosset et al., 2006). Further detailed description of the marbled crayfish is provided by Kawai et al. (2009).

Since this subspecies arose in the pet trade and does not exist anywhere as a wild native population, very little is known about their ideal habitat. However, it may be worthwhile to consider the habitat requirements of its closest relative, Procambarus fallax, which occurs in streams and rivers but seems to prefer lentic or slow-flowing habitats and is typically found in wet prairies, marshes, and sloughs with organic lightweight soils (Hendrix and Loftus, 2000; Martin et al., 2010a). P. fallax also inhabits temporary wetlands, which feature brief dry-downs during which crayfish retreat into burrows (Martin et al., 2010a). P. fallax is considered a tertiary burrowing species, meaning it lives in open water during most of its life and burrows only under high-stress environmental conditions (Dorn and Violin, 2009). Like most crayfish species, P. fallax f. virginalis is an omnivore that feeds on detritus, algae, plants, and invertebrates.

P. fallax f. virginalis is able to tolerate a wide range of environmental conditions, including low oxygenation and temporary exposure to temperatures below 8°C and above 30°C (Seitz et al., 2005; Souty-Grosset et al., 2006; Feria and Faulkes, 2011). There are opposing views as to whether P. fallax f. virginalis is able to invade cold water environments at higher latitudes or altitudes, such as Central or Northern Europe or the Laurentian Great Lakes. While lab results and anecdotal observations suggest that P. fallax f. virginalis is able to tolerate low temperatures (8°C) (Seitz et al., 2005) and is even able to survive direct ice cover (Pfeiffer, 2005; Robbins, 2018), other authors argue that their temperature optimum is considerably higher (18-25°C) than the temperatures in many water bodies at temperate zones, and that they may not have the potential for wide expansion accordingly (Martin et al., 2010a,b). Recent records from Germany indicate that P. fallax f. virginalis is able to form stable, reproducing populations in European temperate zones, but so far this has been documented in lentic habitats only (Chucholl and Pfeiffer, 2010).

The primary pathway for P. fallax f. virginalis introductions is the intentional release of aquarium specimens (Souty-Grosset et al., 2006; Chucholl and Pfeiffer, 2010). Its striking coloration, undemanding nature, and unique reproductive behavior makes this species especially appealing to aquarium hobbyists. However, its parthenogenic traits mean that P. fallax f. virginalis can quickly overpopulate an aquarium. To prevent overcrowding, aquarium hobbyists may try to offload excess stock to other hobbyists -- or to the wild (Souty-Grosset et al., 2006). The fact that P. fallax f. virginalis propagates by parthenogenesis makes the risk of release resulting in a reproducing population considerably greater than for sexually reproducing crayfish species.

The popularity of P. fallax f. virginalis as an aquarium pet increases its probability and risk of establishment in the wild. There is significant concern that its spread in the North American pet trade will almost inevitably result in releases from captivity in the United States (Faulkes, 2010). P. fallax f. virginalis is available through online pet and bait shops and is easily shipped across international and domestic borders (Chucholl, 2010; Peay et al., 2010), and personal contacts between crayfish enthusiasts may lead to even more cross-border acquisitions (Faulkes, 2010).

Summary of species impacts derived from literature review. Click on an icon to find out more...

Environmental	Socioeconomic	Beneficial

Marbled crayfish are reported to tolerate a broad range of environmental conditions, including various pH and oxygen levels, and hobbyists report that they can thrive in unfiltered water “straight from the tap” (Robbins, 2018). Their ability to overwinter in the Great Lakes region is unknown, as they have been reported to survive ice cover in laboratory experiments (Souty-Grosset et al., 2006; Feria and Faulkes, 2011) but do best at temperatures between 18-25°C. As omnivores, this species can utilize a diverse range of food sources, and native predators are unlikely to be able to control their rapidly-reproducing populations. Because of their asexual reproduction and high fecundity, once control measures are stopped, the population is likely to return to its former level (Gherardi et al., 2011).

 Procambarus fallax f. virginalis has the potential for high environmental impact if introduced to the Great Lakes.

This species’ fast growth rate and r-selected life history traits may allow it to outcompete native species (Jones et al., 2009; Chucholl and Pfeiffer, 2010). This species has been documented to carry rickettsiosis, coccidiosis, and Psorospermium sp., and may be a carrier of the crayfish plague (Souty-Grosset et al., 2006). Closely-related species such as P. clarkii degrade wetlands and increase water turbidity, and while this behavior has not been specifically documented in marbled crayfish, high densities of this species may have significant impacts on ecosystem function and integrity (Chucholl, 2010).

Procambarus fallax f. virginalis has the potential for moderate socio-economic impact if introduced to the Great Lakes.

The marbled crayfish is a burrowing species, and have been reported to damage irrigation systems and dams (Souty-Grosset et al., 2006), particularly in rice paddies, where they may also feed on and injure young plants (Jones et al., 2009; Kawai et al., 2009; Heimer, 2010): similar effects may be possible in wild rice paddies around the Great Lakes. Fishermen in Madagascar also report severe negative impacts on their fishing grounds in the presence of marbled crayfish, but currently all evidence is anecdotal (Jones et al., 2009; Heimer, 2010).

Procambarus fallax f. virginalis has the potential for high beneficial impact if introduced to the Great Lakes.

The marbled crayfish remains a popular pet species in Europe and North America (Chucholl, 2010; Faulkes, 2010), and is also used as fishing bait. The marbled crayfish is a useful laboratory model organism for developmental physiology, epigenetics, and toxicology. Its large numbers of genetically identical offspring, rapid reproductive rate, and simple care requirements make it an ideal species for lab research (Vogt, 2008; 2010). Recent publications document its increasing use as model organism and for cancer research (Jirikowski et al., 2010; Rubach et al., 2011).

Note: Check federal, state/provincial, and local regulations for the most up-to-date information.

Biological

No specific data exists on P. fallax f. virginalis control, but native predatory fish may be worth considering. Eels in particular are good candidates to control unwanted crayfish populations and have been shown to be effective in combination with other control methods like intensive trapping (Aquiloni et al., 2010).

Physical

P. fallax is known to be susceptible to drought (Dorn and Trexler, 2007). Provided that P. fallax f. virginalis shares this characteristic, draining habitats for longer periods might reduce confined populations. Mechanical removal through trapping, electrofishing, or other methods can only remove a fraction of the population and requires significant effort to be effective. Once the control measures have ceased, the population will return to its former level (Gherardi et al., 2011).

Chemical

The application of biocides such as pyrethroid insecticides at the very early stages of invasions or in confined habitats may result in complete eradication (Sandodden and Johnsen, 2010). At a larger scale, however, the use of biocides is both expensive and ineffective because of adverse impacts on non-target organisms (Anastacio et al., 1995) and the tendency of crayfish to escape lethal doses by retreating into burrows or by climbing out of the water.