Description: Largest of the hermit crabs found in Northern Ireland, growing up to 4 cm although often appearing larger due to shell. Body is a red-orange colour, but is often mostly hidden by the shell they occupy and in fact their whole body can withdraw inside if a threat is perceived. They will occupy any suitable empty shell and are adapted to live in them: their soft abdomen is curled to match the internal layout of the shell and bears small hooks with which to attach itself. Both their fourth and fifth pair of rear legs are adapted to support the weight of the shell. The first pair of legs bear claws covered in bumps and spines, with the right claw a lot larger than the left claw. No bristles. Short, pointed rostrum. Occasionally hosts parasitic anemone Calliactis parasitica or the hydroid Hydractinia echinata on the shell.

Habitat: Found on rocky, sandy, and occasionally muddy sediment. Often in rockpools and on the lower shore, and in the sublittoral at depths of up to 140 m.

Distribution: Widespread around Britain and Ireland.

Similar Species: Adults/large individuals are easily distinguished but juveniles and smaller individuals could be confused with several other species of hermit crab present in Northern Ireland.

Key Identification Features:

• Largest of the hermit crabs found in Northern Ireland.
• Claws covered in bumps and spines, with the right claw larger than the left.
• No bristles.

Distribution Map from NBN: Pagurus bernhardus at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Pagurus bernhardus at iNaturalist World Species Observations database.

WoRMS: Pagurus bernhardus at World Register of Marine Species. Accepted name: Pagurus bernhardus (Linnaeus, 1758). AphiaID: 107232.

Classification: Biota; Animalia; Arthropoda; Crustacea; Multicrustacea; Malacostraca; Eumalacostraca; Eucarida; Decapoda; Pleocyemata; Anomura; Paguroidea; Paguridae; Pagurus