Gammarus (Camarus)

A group of gammarus (Camarus) under a river pebble.

A predatory caddisfly larva and leeches can also be seen in the picture.

That's how it should be, that would be ideal. Unfortunately, this is no longer the case in many rivers because the stream beds have become completely hardened by fine sediments, among other things, and the gammarus and many other macrozoobenthos no longer have the opportunity to make their home under a river pebble.