Freshwater Shrimp
Gammarus pulex
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Not an insect and not really a shrimp — but it is what half the burn's food chain runs on.
A small, curved, flattened crustacean, grey-brown and translucent, that swims on its side in short darting bursts. It is not an insect but an amphipod, and not a true shrimp either. Gammarus is abundant under stones and among leaf litter in clean burns, ditches and river margins throughout the Dumfries area, often in enormous numbers.
Behaviour
Freshwater shrimps shred fallen leaves and detritus, and in doing so they are the main engine that converts autumn leaf-fall into food the rest of the stream can use — which makes them one of the most important animals in a burn. They are eaten by trout, bullhead, dippers and water shrews. Pairs are often found swimming clasped together, the male carrying the female for days before she moults.
When to see it
Quick facts
- Family
- Freshwater amphipods (Gammaridae)
- Size
- 11–20 mm
- Status
- Native; abundant, and a keystone of the stream food web
Photo by Nicola Simoncini, CC BY 4.0, via Wikimedia Commons