Antenna 2 usually with swimming setae, flagellum 2 bi-articulate; mandibular palp absent; outer lobe of maxilliped larger than, or equal to, inner lobe; gills on pereonites 3 and 4;pereopods 3 and 4 absent, pereopod 5, six-segmented; abdomen of male with one pair of appendages and one pair of lobes, female with one pair of lobes.
It is under debate whether Metacaprella represents a true genus. For this reason, Metacaprella spp. have been included under Caprella. See: Caprella kennerlyi, C. anomala, C. ferrea and C. horrida.
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.
