Photo credit: Klaus Rudloff/ firstname.lastname@example.org/ Berlin, Germany/http://www.biolib.cz
(Procambarus fallax f. virginalis)
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Species at a Glance
The marbled crayfish, also called the marmorkreb (which is German for “marbled crayfish”), is a parthenogenetic female crayfish thought to be a form of the slough crayfish (Procambarus fallax). Therefore, it has been designated an informal subspecies, although some researchers have proposed a new species designation, Procambarus virginalis. There are no known native populations of this crayfish, and the only known cases of it in the wild are where it has been introduced by humans.
This medium-sized crayfish has a distinct marbled color pattern and a small pincer-like claw called a chelae. Coloration can differ depending on its diet, occasionally showing blues or greens. The total length is up to 13 cm (5 in), but it is more often found less than 10 cm (4 in). The upper side of the carapace is smooth, while the sides are slightly granulated.
The marbled crayfish is closely related to the slough crayfish (Procambarus fallax), which is widely distributed across Florida and has similar coloration and general appearance. Distinguishing these species can be difficult because only female marbled crayfish exist, making it difficult to use identification keys that rely on characteristics of the male gonopods.
Since there are no indigenous populations of the marbled crayfish, its habitat requirements are often assumed from its closest relative, the slough crayfish. This crayfish can occur in streams and rivers, but seems to prefer still or slow-flowing habitats and is typically found in marshes, wet prairies, and sloughs with lightweight organic soils. It also inhabits temporary wetlands where it can retreat into burrows during dry periods.
Spread of the marbled crayfish through the pet trade increases the probability of it being released into natural ecosystems. It is the only known decapod crustacean species to reproduce through parthenogenesis, and therefore, all individuals are female and only one is needed to establish a new population. Because each crayfish is genetically identical, easy to care for, and has high reproductive rates, it is also popular in labs as a model organism for studying development.
The marbled crayfish was discovered in Europe in the 1990's. It has since been introduced to multiple countries on three continents, including Germany, Sweden, Hungary, the Netherlands, Italy, Slovakia, Madagascar, and Japan. While some believe the marbled crayfish originates from the southeastern United States, indigenous populations have never been reported and there are no confirmed introduced populations of this species in the United States.
Note: Distribution data for this species may have changed since the publication of the Mid-Atlantic Field Guide to Aquatic Invasive Species (2016), the source of information for this description.
Because of its high reproductive rate and the need for only one individual to start a population, this species is considered a serious future threat to aquatic biodiversity in regions where it becomes established. It is a voracious feeder and consumes a broad range of aquatic plants and invertebrates, putting it in competition with native aquatic flora and fauna.
Information for this species profile comes from the Mid-Atlantic Field Guide to Aquatic Invasive Species (2016).