Description: A small pea crab that lives inside bivalves and ascidians. The carapace is smooth and usually has a brown colouration, although sometimes it can have a red hue. The pincers and walking legs are lighter brown. The antennae are very small. The pincers are equal in size and are also smooth. The final section of the walking legs is long (noticeably longer than that of Pinnotheres pisum). In females the carapace is softer, translucent and more square-shaped than that of the male which is hard, opaque and oval in shape. The region between the eyes is curved only very slightly downwards.

Habitat: Reported from lower shore to around 100 m depth, usually found within ascidians (e.g. Ascidia, Ascidiella, Pyura and Microcosmus) and occasionally within bivalves (e.g. Modiolus, Pinna and Ostrea).

Distribution: Rarely recorded around Britain and Ireland. There are no records from Scotland or the east coast of Britain.

Similar Species: Could be confused with Pinnotheres pisum. The final section of the walking legs in Nepinnotheres pinnotheres is much longer, and the region between the eyes is only slightly downturned.

Key Identification Features:

• A small pea crab (M 13 mm; F 8 mm) that lives inside ascidians or occasionally bivalves.
• Brown coloured carapace, occasionally with a red hue. Lighter brown pincers and walking legs.
• Final section of walking legs long (not short and curved, as in P. pisum).
• Region between the eyes only slightly downturned.

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

iNaturalist: Nepinnotheres pinnotheres at iNaturalist World Species Observations database.

WoRMS: Nepinnotheres pinnotheres at World Register of Marine Species. Accepted name: Nepinnotheres pinnotheres (Linnaeus, 1758). AphiaID: 107469.

Classification: Biota; Animalia; Arthropoda; Crustacea; Multicrustacea; Malacostraca; Eumalacostraca; Eucarida; Decapoda; Pleocyemata; Brachyura; Eubrachyura; Thoracotremata; Pinnotheroidea; Pinnotheridae; Pinnotherinae; Nepinnotheres