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Species of the month

Common Hermit Crab

Pagurus bernhardus

Some facts on this crab:

Carapace length: Up to 4.5 cm.

Body length: Up to 8 cm.

Habitat: Rocky and sandy substrata from mean tide level to 140 m. depth.

Range: European and North American coastal waters.

Diet: Mainly detritus (decomposing organic matter).

First described: By the Swedish naturalist Linnaeus in 1758, who originally named it Cancer bernhardus.

Pagurus bernhardus chooses its home and carries it on the back wherever it goes. The body of this hermit crab lacks a hard, protected carapace. Without a shell it is extremely vulnerable to predators, so it searchs for an empty snail shell (for example whelk or periwinkle) and adopts it for an home. The availability of suitable shells is often limited, which leads to intense competition among the crabs for shells of the proper size and condition. This crab often grows in the shell the sea anemone Calliactis parasitica which helps to protect the crab with its nettling tentacles, and in exchange enjoys the crab's food. Pagurus bernhardus, which is a reddish or brownish crab, walks on its second and third pairs of legs and uses the strongly reduced fourth and fifth pairs to grip the central column of the snail shell and to circulate breathing water. The genus Pagurus contains some 180 species and belongs to the hermit crab family Paguridae, along with 79 other genera.