Emerging largely un-noticed from the wet sand at low tide level at Rhossili Bay, Gower Peninsula, this small crab seems to be pushing up at least its own weight in sand.
Rinsed off in some standing water on the shore, you can see a few more details which allows me to suggest it is Pennant’s Swimming Crab, Portumnus latipes (Pennant).
This crab lives on the sand at low tide level and in the sublittoral up to a depth of 150m. It frequently buries itself in the wet sand to a depth of a couple of centimetres – as this individual had done to protect itself when the tide was out.
The crab in the two pictures below didn’t survive its burial in the sand; perhaps trodden on by one of the many surfers who use this stretch of the beach. However, its demise makes it possible to demonstrate the diagnostic features of the species more clearly.
The carapace is about 2 cm long and it is slightly elongate and heart-shaped, reddish with white mottling. Between the eyes there are three blunt ‘teeth’ of which the central one is a bit longer. The front claws of chelipeds are more or less the same size and are usually held under the carapace. The back legs end with a flattened leaf-shaped or spear-shaped segment or pereopod that acts like a paddle to help it swim.
You can find more information about Pennant’s Swimming Crab and other British crabs on the Glaucus web site.
Revision of a post first published 13 May 2009
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