Killer Shrimp

Killer shrimp has a typical laterally compressed, arched, and semi-transparent body. The maximum reported body length is 30 mm (Nesemann et al. 1995). The species demonstrates pigmentation polymorphisms, with striped, spotted and uniform morphs. Other prominent morphological features of the species include large and powerful mandibles that make it an effective predator (Mayer et al., 2008). Juvenile individuals resemble adults, but are much smaller in size. Their growth undergoes a number of moultings. Detailed descriptions of D. villosus morphology can be found in Carausu (1943), Eggers and Martens (2001), and Konopacka (2004).

Killer shrimp are a recent invader of Central and Western Europe freshwater ecosystems. Killer shrimp are originally native to the lower reaches of the rivers discharging into the Black and Caspian Seas (Dedju 1967; Nesemann et al. 1995; Vaate et al. 2002). They are widely distributed in the lower reaches of the Danube River system in the region of Eastern Europe/Ukraine (Mordukhai-Boltowskoi 1969; Nesemann et al. 1995). Its original distribution was restricted to the lower Danube by the narrow valley of the Dunakanyar near the confluence of the Danube and Ipoly Rivers (Nesemann et al. 1995).

This species has been nicknamed the “killer shrimp” for its extremely aggressive behaviour towards native invertebrate species. Due to their large body size and well developed mouthparts, killer shrimp are effective predators, which kill or simply bite off much more prey than they can consume (Dick et al., 2002).

In all the European aquatic systems where it has become established, D. villosus has largely replaced both indigenous and exotic amphipod species (Kelleher et al. 1999). In addition, this species readily consumes fish eggs (Casselato et al. 2007) and even attacks fish larvae (Schmidt and Josens, 2004). Due to its predatory activities, D. villosus significantly changes natural food webs of invaded ecosystems and occupies high trophic levels comparable to fish (Van Riel et al. 2006).