Metacaprella anomala (Mayer 1903)

Length: 5.5-17 mm. Head with one pair anteriorly pointing spines, pereonites 1 to 4 smooth dorsally except for an unpaired spine posteriorly on 4, pereonite 5 has three pairs of spines, 6 and 7 two pairs each; lateral spines may be present over the bases of the second gnathopods, antero lateral spines on pereonites 3 and 4, and over gills. Antenna 1 longer than cephalon plus pereonites 2, 3 and 4. Antenna 2 equals peduncle of antenna 1; flagellum has long swimming setae. Gnathopod 1 propodus and dactylus with serrate grasping margin. Gnathopod 2 propodus palm with proximal grasping spine and accessory spine, distal poison spine and more distal triangular projection; dactylus evenly tapered; basis attached posterior to the middle of pereonite 2, and with antero-lateral ridge. Gills oval. Pereopods 5, 6 and 7 with proximal grasping spines on propodus. Female differs in showing no elongation of pereonite 1; some spines present on anterior body segments.

Japan, California, Washington, Alaska. Probably amphi-Pacific

It is under debate whether Metacaprella represents a true genus. For this reason, Metacaprella spp. have been included under Caprella. See: Caprella anomala

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.

Intertidal on hydroids; sub littoral to 100 m. 6.3 to 14.8°C.

Easily distinguished from Caprella kennerlyi (previously grouped together as Metacaprella) by antenna 1. Distinguished from Caprella ferrea and Caprella alaskana by head spines rather than tubercles and long flagellum of antenna 1.