‘Killer shrimp’ in German waters: This is what a small animal does

Big shrimp, also known as “killer shrimp”, have been common in German rivers as well as in Lake Constance for years.

© Felix Kästle / dpa

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The ‘large flea crustacean’ lives as an invasive species in German rivers and Lake Constance. It is also known as “killer shrimp”. Maybe a mistake?

No, we did not come up with this name for this type of crabs – “large amphibians” (Dikerogammarus villosus) are already known in English-speaking countries under the name “shrimp killer”. Although the size of the predatory amphipod is usually only two centimeters, it is a sly old dog. “Killer shrimp” is not native to Germany, but has been found in German rivers for nearly 30 years.

It lives as a ‘newozoa’, i.e. as an invasive species, in almost all German water systems and can cause serious damage. “Large flea crustaceans” can now be found not only in German rivers, but also as far as Lake Constance.

Invasive species in German rivers: ‘killer shrimp’ causes terror – wrong?

As reported by the German Union for the Conservation of Nature (NABU), the “large flea crustaceans”, the “killer shrimp”, migrated through the main Danube Canal to the Rhine in the 1990s and from there spread explosively throughout Europe. But why is “killer shrimp” so dangerous? Or does the reputation of giant amphibians possibly mistakenly precede it?

By itself, the larger amphibians are harmless to humans. But like most invasive species in Germany, “killer shrimp” poses a threat to native fauna, but in a different way than lobster plague. According to NABU, experiments have noted that “under laboratory conditions, this type of predator behaves significantly more than the freshwater shrimp, which are its original relatives. It is also known that other types of invertebrates became rare or even disappeared during the migration of the giant amphipods” .

‘Killer shrimp’: a threat to native amphipods – but not as a predator

Researchers at the University of Koblenz-Landau have already discovered that the feeding habits of giant amphibians vary across water bodies, depending on conditions. According to the first findings, the Elbe “killer shrimp” is not a “real” predator, as reported by NABU.

The consequences for the immigrant “do not appear to be nearly as severe, at least in the Elbe, as previously assumed. Direct damage to native species by dumb shrimp cannot be demonstrated.” NABU asserts: “This does not necessarily mean that the large shrimp is not a problem for our waters. Because: As another research team discovered, ‘killer shrimp’ indirectly but significantly led to the mass extinction of the original amphipods.

Invasive species in Germany: Killer Team – ‘Killer Shrimp’ and the Black Mouth Goby

A 2016 study by the Technical University of Munich found that amphibians do not overeat many of their relatives, such as, among other things. ghost I mentioned at the time. But: “Killer Shrimp” occupy the burrows and lairs of small local crabs and take them out of their lairs. Without shelter, native amphibians are more quickly caught by predators.

In German rivers there is a dangerous duet to the original amphipods – the “killer shrimp”, which, in fact, is not one, is part of the deadly team. to me ghost Another “neoson” is part of the problem – the “black-mouthed goby” (Neogobius melanostomus). The introduced brackish and freshwater fish may also prefer to eat the indigenous amphibian (Gammarus pulex). “Killer shrimp” pushes native amphibians out of their hiding places – black mouthed gobies take advantage of this during their invasion and it’s easy for them to capture and eat native amphibians without hiding.

By the way, there are not only invasive species in Germany that pose a threat to our native animals. The Asian tiger mosquito, for example, is also a problem for humans – it is considered the “most dangerous animal in the world” and is prevalent in Baden-Württemberg. The orb spider is also dangerous to humans – even a bite from this invasive spider can even lead to death.

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