Description: A medium-sized swimming crab with a dark brown carapace reaching up to 30 mm. Some fine ridges on the carapace, and occasionally it also has bristly hairs at the back. No teeth between the eyes, but there are hairs/bristles. Five teeth either side of carapace that vary in size: the fourth being the smallest (sometimes almost not visible), the third and fifth pointed. Pincers are relatively smooth and equal in size. Legs usually lighter in colour than the body with a very fine ridge running down the legs.

Habitat: Gravel and sand are the usual habitat, down to a depth of 70 m. Reported to be found occasionally on Zostera marina (seagrass) beds. Rarely found on lower shore.

Distribution: Found around most coasts of Britain and Ireland.

Similar Species: Could be confused with other Polybius sp. but this species has no teeth between the eyes.

Key Identification Features:

• Smooth region between the eyes (no teeth), but with bristles.
• Five teeth either side of carapace, of unequal size.
• Fourth teeth very small, can be almost obsolete.
• Third and fifth teeth pointed.

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

iNaturalist: Polybius navigator at iNaturalist World Species Observations database.

WoRMS: Polybius navigator at World Register of Marine Species. Accepted name: Polybius navigator (Herbst, 1794). AphiaID: 1752525.

Classification: Biota; Animalia; Arthropoda; Crustacea; Multicrustacea; Malacostraca; Eumalacostraca; Eucarida; Decapoda; Pleocyemata; Brachyura; Eubrachyura; Heterotremata; Portunoidea; Polybiidae; Polybius