pagurus

Pagurus is a genus of marine decapod crustaceans in the family Paguridae, commonly called hermit crabs. Species in the genus inhabit a range of benthic environments and are characterized by a soft, elongate abdomen that is rolled under the thorax to fit inside a gastropod shell, which provides protection as they lack a hard dorsal carapace covering the abdomen. They retain the chelae (claws) of the front body segments, with some species showing asymmetrical claws.

They are obligate shell-dwellers, acquiring and abandoning shells as they grow. They actively select shells that fit their size, and may compete with conspecifics or other hermit crabs for suitable shelter. When not in shells, they live in crevices, under rocks, or among stones in intertidal to subtidal zones.

They have a wide, often cosmopolitan distribution in temperate and tropical seas, from shallow shores to continental shelves. They are typically scavengers and omnivores, feeding on dead organic material, algae, and small invertebrates. Reproduction involves females carrying eggs under the abdomen until hatching; larvae are free-swimming and pass through zoea/nauplius-like stages before settling as juvenile crabs.

The genus contains numerous species; estimates commonly place the number at around 50–60. Notable species include Pagurus bernhardus, the common European hermit crab, and Pagurus longicarpus, the long-clawed hermit crab of the western Atlantic.