Caprella mutica Schurin, 1935
Caprellid, "Ghost" or "Skeleton" shrimps, so called for their skeletal appearance. Amphipod crustaceans, easily distinguished by the elongate stick-like body form and reduction of the abdominal appendages. Head is generally fused with pereonite 1. Pereopods on first 2 segments (pereonites) are most flexible and called gnathopods; gnathopods 2 being the largest, used in defense, feeding and substrate attachment. In many species pereopods 3 and 4 may also be reduced or absent. Gills on pereonites 3 + 4, rarely on pereonite 2. Pereopods 5 - 7 much smaller than 1 + 2, used for clinging to the substratum. In females, brood plates (öostegites) develop on pereonites 3 + 4. Much remains to be learnt about their biology, ecology and in many cases changing distributions.
Length: 6-49mm. Head rounded. Most extreme body projections described here (fully developed adult male): Cephalon and pereonite 1 smooth (although with dense long setae, which also extend over gnathopod 2); pereonite 2 with 1-3 pairs dorsal spines and 2 pairs lateral spines (base of gnathopods 2 and posterior); pereonite 3 with 7 pairs dorsal spines and 3-7 spines near attachment of gills; pereonite 4 with 8 pairs dorsal spines and 3-7 spines near attachment of gills, 1 pair lateral spines at both anterior and posterior margin; pereonite 5 with 5 pairs dorsal spines, 1 pair antero-lateral spines; pereonites 6 and 7 with 2 pairs of spines dorsally (median and posterior). Antenna 1 longer than ½ body length. Antenna 2 less than ½ length of antenna 1; peduncle with two ventral rows of setae. Gnathopod 1 short, with setation on posterior margin; propodus with 2 grasping spines, grasping margin of dactylus and propodus serrate. Gnathopod 2 long, densely covered in setae; propodus palm with large projection proximo-medial and a distal triangular projection ; dactylus heavy and scimitar-shaped; basis having an antero-lateral projection distally. Gills oval to elliptical. Pereopods 5 - 7 propodus with 2 grasping spines. Females differ in presence of 1 pair spines on cephalon and posterior of pereonite 1 (not always present)
Introduced throughout the northern hemisphere and to New Zealand in the southern hemisphere. Very abundant during summer months. Distinguished from C. acanthogaster: pereonite 2+3 covered in fine setae in mature male, gnathopod 2 poison spine less developed, gills are shorter.
National Museum of Natural History, Washington DC: (NMNH); University of Alaska, Fairbanks
Ecology and Distribution
Native to Sea of Japan (Russia and Japan); introduced widely in northern hemisphere and New Zealand in the southern hemisphere.
In fouling communities on floats and pilings, on many substrates (hydroids, bryozoans, ascidians etc.)
- Caprella macho Platvoet et al., 1995 (synonym)
- Caprella acanthogaster humboldtiensis Martin, 1977 (synonym)