Invertebrates
Freshwater Shrimp
Gammarus pulex · also called scud
Lift a stone from a clear stream and a freshwater shrimp may wriggle out, curled like a comma and swimming sideways into the current.
Overview
The freshwater shrimp, Gammarus pulex, is an abundant small crustacean of clean streams, rivers, and lakes across Europe. Its leaf-shredding, mate-carrying, and role as food for fish and birds make it one of the most important invertebrates of freshwater ecosystems.
A shrimp that feeds the stream
By shredding fallen leaves, the freshwater shrimp turns tree litter into food for the rest of the stream, and in turn is eaten by trout and many other animals.
Status
Not Evaluated, but abundant in clean water.
Freshwater Shrimp: common questions
Is the freshwater shrimp a true shrimp?
No, it is an amphipod, a different kind of crustacean, with a curved, sideways-flattened body.
Why does it carry its mate?
The male carries the female beneath him for days before she moults, and then mates with her.
Why is it a sign of clean water?
It is sensitive to pollution, so large numbers in a stream suggest the water is healthy.
Where is the freshwater shrimp found?
It lives in streams, rivers, and lakes with clean, flowing water across Europe.