Description: A small swimming crab reaching a carapace length of 20 – 25 mm. Surface of the carapace can be smooth to granular with prominent transverse ridges. Colour can be very varied ranging from yellow-orange to brown carapace, sometimes with central band of white or yellow, and sometimes displaying banded legs. Three broad, rounded frontal lobes, with the middle lobe being the widest. Five teeth either side of the carapace. The first tooth is broad and rounded, the second to fourth are smaller but still rounded, however the fifth is noticeably pointed and more prominent than the others. Pincers are equal in length and quite stout. Fifth pair of legs adapted for swimming, ending in small paddle.

Habitat: Sandy and stony bottoms, from intertidal to 100 m

Distribution: Found all around the coasts of Ireland and Britain.

Similar Species: Could be confused with other Polybius sp.

Key Identification Features:

• Small adult size
• Three rounded frontal lobes, the central one most prominent.
• Five teeth on either side of carapace; first four teeth rounded, with the first the most broad, and the fifth tooth prominent and noticeably pointed.

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

iNaturalist: Polybius pusillus at iNaturalist World Species Observations database.

WoRMS: Polybius pusillus at World Register of Marine Species. Accepted name: Polybius pusillus (Leach, 1816). AphiaID: 151200.

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