Description: Usually a pale red or yellow in colour, this spider crab reaches a size of up to 12 mm. The carapace is relatively smooth but it does have a number of hook-shaped bristles on its surface. There is a small u-shaped rostrum between the eyes, which are on prominent eyestalks that have a prominent bump on them. Males have chunkier pincers than the females, and there are bristles on them. The walking legs are slender and have many long hook-shaped bristles on them, and are lighter in colour than the body.

Habitat: Found from 5 m – 70 m, and frequently hiding amongst animal turf (e.g. hydroids, bryozoans and ascidians). Also found under boulders or camouflaged amongst algae.

Distribution: Scattered records around the coasts of Britain and Ireland. Few records from east coast of Britain, and few records from Irish coast.

Similar Species: Could be confused with other spider crabs that are similar in size.

Key Identification Features:

• Red – yellow in colour, usually pale but can vary.
• Relatively smooth carapace covered in hook-shaped bristles as are the pincers and walking legs.
• U-shaped rostrum.
• Prominent eyestalks with a noticeable protrusion.

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

iNaturalist: Achaeus cranchii at iNaturalist World Species Observations database.

WoRMS: Achaeus cranchii at World Register of Marine Species. Accepted name: Achaeus cranchii Leach, 1817. AphiaID: 107313.

Classification: Biota; Animalia; Arthropoda; Crustacea; Multicrustacea; Malacostraca; Eumalacostraca; Eucarida; Decapoda; Pleocyemata; Brachyura; Eubrachyura; Heterotremata; Majoidea; Inachidae; Inachinae; Achaeus