Length: 8.5-13.6mm. Spination of head and body highly variable: anterior pereonites may be smooth with blunt dorsal spines showing only on pereonites 5 to 7; or there may be dorsal spines on all pereonites and on head; antero-lateral projections on pereonites 3 and 4 always present. Antenna 1 very long, equal to distance from head to pereonite 5 inclusive; flagellum shorter than second peduncle article. Antenna 2 shorter than 2 basal articles of antenna 1, flagellum with short setae. Gnathopod 1 with strongly serrate grasping margin to propodus and dactylus. Gnathopod 2 propodus length more than twice width; palm with proximal grasping spine and accessory spine, median to distal poison spine, distal triangular projection. Basis attached posteriorly on pereonite 2, slender with small antero-lateral ridge. Gills oval. Pereopods 5 to 7 increasing in length, propodus with proximal grasping spines. Female differs from male in being spinier; no lengthening of anterior pereonites; gnathopod 2 arises anteriorly.
California, Oregon, Washington, Alaska
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 bryozoans and sabellid worm tubes.
Range from very spiny to those almost spineless. C. ferrea and C. alaskana are extremely difficult to differentiate as juveniles. As adults, C. alaskana is number more slender and C. ferrea has a rougher body surface, always has head spines and frequently small tubercles laterally on anterior pereonites. Pereonite 5 in C. alaskana is usually longer than 6 plus 7 and shorter in C. ferrea.
