Killer shrimp (D. villosus) is a monopod native to the Basin of the Black Sea and the Caspian Sea, with a body length of only 30 mm, known for its rapid growth and amazing fecundity. A recent survey showed that these humble little things are using the Danube and its tributaries to expand and become invasive species that dominate Europe's major rivers. Previously, there were reports that the relevant departments in the United States were worried that killer shrimp spread to the Great Lakes of North America through the ballast water of ships, threatening the local ecological environment like Asian carp.
The killer shrimp adapts to extreme environments of 0-30 °C, low oxygen concentration and 20% salinity, and can be found in lakes, canals and rivers in various substrates. Killer shrimp eat an astonishing amount of food, mainly preying on insect larvae and fish eggs, and strong and powerful upper and lower jaws can easily tear prey into pieces. Native species are nearly extinct due to lack of food, and ecosystems are on the verge of collapse.
A new study found that fear of killer shrimp has spread to rivers throughout Europe, and even if killer shrimp don't attack, their presence is enough to make other species shudder.
Gammarus, a native freshwater shrimp that has survived in Europe for 30 years, is considered a key species in the local ecosystem, playing an important role in chopping up fallen leaves and making them food for other species.
Scientists at the University of Plymouth in the United Kingdom have carefully studied the predatory effects of killer shrimp and found that in addition to consuming biological resources, killer shrimp can also cause a pronounced fear response of hook shrimp.
The researchers put a closed cage containing killer shrimp into a tank where hook shrimp were raised, and found that the hook shrimp that shared the "killer" had a significantly lower efficiency in cutting leaves. Over time, enemies apparently no longer pose any threat, but the efficiency of hooked shrimp cutting leaves has become less efficient. What's even more amazing is that these hook shrimp have never been in contact with killer shrimp before. In other words, the fear of killer shrimp has become a natural reaction to hook shrimp.
Biologist Mark Briffa said the experiment showed that the presence of invasive predators can affect the feeding behavior of native species, causing a huge non-expendable impact on the local ecological environment.
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