15 Feb 2025: Shrimps at Bishop's Pond

Not actually in the pond, but under logs, these are not the familiar seawater shrimps, or even the freshwater “shrimp” (Gammarus). Like the Gammarus and the sandhoppers (Talitrus) found in heaps of rotting seaweed on beaches, these are amphipod crustaceans. The ones we found today might be Arcitalitrus dorrieni, the Landhopper, Woodhopper or Lawn Shrimp, or perhaps Cryptorchestia garbinii. You can see a photo and more information at https://bmig.org.uk/species/arcitalitrus-dorrieni.

We'll need to catch one to inspect it more closely, but as soon as they are uncovered, the little blighters immediately leap about all over the place, like large demented fleas. Also under the logs, but less surprising, are woodlice, which are isopod crustaceans. Isopods are flattened from top to bottom, whereas amphipods are flattened from side to side, and therefore tend to fall over on to their sides. Both need to live in damp places, if not actually in water like most other crustaceans, because they need to keep their gills moist in order to breathe.