Invasive species
Faxonius limosus
racul dungat
Spiny-cheek Crayfish
Kamberkrebs
écrevisse américaineracul dungatSpiny-cheek CrayfishKamberkrebsécrevisse américaineSlender, medium-sized crayfish; adults range from 6 to 12 cm in total length. The colour varies from olive-brown to dark brownish-black, sometimes bluish, with characteristic reddish-brown bands on the abdominal segments and pleurae. The ventral surface of the claws is lighter, with an orange tip banded with black — visible on the ventral side. A curved spine is present on the inner margin of the carpus. The rostrum is elongated with parallel margins terminated by spines. The apex is long and sharp. There is a single long postorbital ridge terminating anteriorly in a spine. The cephalothorax is smooth with spines only in the cervical region and the sides of the cephalic area. A robust spine is present on the ventral surface of the ischiopodite of the third pair of legs.
Deliberately introduced to Europe in 1890 via an import from North America into a fish pond at Barnówko (Poland), its range has since expanded to cover much of western and central Europe — from France, Great Britain, and Italy to Serbia, Romania, Poland, Belarus, and Lithuania (Souty-Grosset et al. 2006). In Romania the species was first recorded in the Danube (Pârvulescu et al. 2009). Its Romanian range currently overlaps only with that of the Narrow-clawed Crayfish (Astacus leptodactylus). For the distribution map, visit the distribution page.
Claw size is not a reliable indicator of sex in this species. To distinguish the sexes with certainty, examination of the sternal plate and pleopods is required. In males the first two pairs of pleopods are strong and oriented anteriorly (for spermatophore transfer), while in females all pleopods are equal. The shape of the first two male pleopods is an important criterion for distinguishing this species from similar ones: the first pleopod (Pl. I) has a distal lobe almost 2/3 of the total length, while the second pleopod (Pl. II) has an exopodite approximately 4/5 of the endopodite length, the distal lobe of the endopodite being approximately 1/5 of its length and strongly twisted.
Prefers turbid, muddy waters in lowland areas — large rivers, canals, lakes, and fish ponds. In North America it has been recorded even in rocky-bottomed streams with moderate current. In Europe it occupies a broad range of habitats including cold, fast-flowing waters, though it prefers deep, calm waters and is frequently encountered in ponds and lakes. Active both day and night, consuming almost any food; adults frequently eat plant material. Highly resistant to low oxygen concentrations and poor water quality — a major advantage in its invasion process. Can survive several days out of water. Natural predators include otter, muskrat, rat, mink, coypu, fox, badger, and water birds (adults) and fish (juveniles), particularly wels catfish, pike, perch, and sturgeons. It is highly resistant to parasitic diseases, including the oomycete Aphanomyces astaci, against which it possesses antibodies — making it a carrier of crayfish plague lethal to native species. Ectoparasitism without apparent damage is frequent, involving branchiobdellids, chironomids, and ostracods. Bivalve colonies (Dreissena sp.) are often attached to adults.
A major advantage over native crayfish species is the high reproductive capacity of this species. Spiny-cheek Crayfish mate in autumn, spring, and even during winter, when females carry white spermatophores on the sternal plate. The clutch is large, reaching around 400 eggs, and is carried by the female among the pleopods until juveniles become independent — in as little as 6–7 weeks. Age can be estimated from total length: 0+ = 18–30 mm; 1+ = 40–65 mm; 2+ = 65–80 mm; 3+ = 80–95 mm; 4+ = 95–110 mm. Moulting is more frequent in juveniles (up to 4–5 times per year); adults moult once or twice per year, usually in spring–summer. The days immediately following a moult are critical — without the hardened exoskeleton the crayfish is vulnerable to attack by fish or other crayfish. Lost appendages regenerate at the next moult but usually reappear smaller. Sexual maturity is reached after the first year of life, at a total length of approximately 50–65 mm.
