Species description: This is a large caprellid, with males reaching up to 45 mm in length, females are smaller and grow to around 15 mm. It usually has an overall orange to red colouration, often with spotting. The first segment of the body (after the head) is especially long. The antennae are also long. There are distinct acute projections or spines along the back, although the head and first two segments are smooth. In males the first two body segments and the gnathopods are covered in hairs. Females have a red-spotted brood chamber, noticeable as a pouch on their underside. Pereopods 3 and 4 are absent or poorly developed.

Habitat: In harbours and marinas, on pontoons, mooring ropes etc., and on or near aquaculture sites, or on mussel beds. Can also be found on natural substrata such as algae and hydroids.

Distribution: A non-native species that is now spreading. Recorded from most coasts in Britain and Ireland, very few records from east coast of Britain. Likely to continue to spread.

Similar Species: Could be confused with other caprellids but the red spotted brood chamber, and red colouration in general helps to distinguish (although colour alone cannot be relied upon and other characters should be checked). Males also grow larger than our native caprellids.

Key Identification Features:

• Large caprellid (male 45 mm, female 15 mm).
• Red to orange colouration.
• Second body segment (behind head) especially long.
• Females have a red-spotted brood chamber.
• Spines along back, but absent from head and first two body segments.

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

iNaturalist: Caprella mutica at iNaturalist World Species Observations database.

WoRMS: Caprella mutica at World Register of Marine Species. Accepted name: Caprella mutica Schurin, 1935. AphiaID: 146768.

Classification: Biota; Animalia; Arthropoda; Crustacea; Multicrustacea; Malacostraca; Eumalacostraca; Peracarida; Amphipoda; Senticaudata; Corophiida; Caprellidira; Caprelloidea; Caprellidae; Caprellinae; Caprella