Mediterranean Hermit Crab

• When an empty shell turns up, several hermit crabs may line up by size and hand the shells on in a chain, each moving into the one the previous crab has left.
• It reappeared on the coasts of south-west England in 2016, after almost three decades without records, in a shift linked to the warming of the sea.
• It occupies empty gastropod shells, above all of Littorina striata, Mitra, Nassarius incrassatus and Stramonita haemastoma, and changes them as it grows.
• Its scientific name literally means chain-mailed soldier with red legs.
• In the United Kingdom it has a curious history: it was an occasional visitor to the south coast of Cornwall until it all but vanished after the Torrey Canyon spill in 1967.
• It reappeared there in 2016, almost half a century later, probably from larvae arriving from Brittany or the Channel Islands. A later study found that all the British individuals were very similar in size, a sign of a single colonisation event, and recorded the most northerly egg-bearing female known for the species.

Skeleton type

Invertebrate - articulated calcareous exoskeleton (crustacean)

Habitat and environment

Intertidal pools and shallow rocky bottoms of the Mediterranean and the nearby Atlantic

Sources consulted: Latreille (1818); Marine Life Information Network (MarLIN); Cornwall Wildlife Trust; Marine Biodiversity Records (2020); ScienceDirect (Hughes 1989); Science Advances, How colonial animals evolve; Wikipedia, Zooid