Length: 3.5-15mm. Head with large, triangular, anteriorly directed projection anterior to eye. Dorsal surface smooth. Antenna 2 longer than peduncle of antenna 1. Gnathopod 1 propodus with 2 proximal grasping spines, grasping margin of dactylus and propodus serrate. Gnathopod 2 attached anterior to median of pereonite 2; propodus palm setose, with proximal projection, concave palm with distal elevated rectangular projection; grasping margin of dactylus serrate. Gills circular, oval or elliptical. Pereopods 5 - 7 propodus palm slightly concave with proximal grasping spines.
Cosmopolitan: England; France; Spain; China; Western Australia; New Zealand; South Africa; Gulf of Mexico; N + S America; Caribbean; Hawaii
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.
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.
Generalist. Found on red and brown algae, hydroids, sponges, bryozoa; intertidal exposed areas and infralittoral areas of high hydrodynamics.
McCain 1975 notes that Monterey Bay "may be the northern limit of C. penantis and the southern of C. natalensis" (but the latter was subsequently reported from deeper water off southern-California by Watling [1995]). C. penantis differs from C. natalensis in ratio of length of pereonite segments, palm of gnathopod 2 propodus and in abdomen of males and females. C. penantis tends to be stouter than C. natalensis. Laubitz (1972) provides a guide to the differences between C. natalensis and C. penantis.
National Museum of Natural History, Washington DC: (NMNH) 1105501*; (NMNH) 104136* (labeled Caprella geometrica); (NMNH) 21664; Cold Springs, Long Island; Acc 34616 (labeled Caprella geometrica)
