Description: Family Caprellidae ("skeleton shrimp") are distinctive-looking. Their long, stick-like bodies are composed of a cephalon (head), pereon (thorax), and a tiny abdomen. The vast majority of the body is the pereon. Caprellids have two pairs of antennae, and the first pair is usually the longest (photo). The first two segments (pereonites) of the pereon have large legs (pereopods) called gnathopods (photo). The gnathopods are large, usually subchelate claws, and are used to capture prey and to grasp the substrate as they move around. Pereopods 3 and 4 are usually reduced or absent, but pereonites 3 & 4 (and 2 on some species) have pairs of leaf-like gills. Females also have a marsupium (pouch) on pereonites 3 & 4 in which they carry the eggs or young (photo). Pereonites 5-7 have a set of 3 smaller pereopod pairs at the posterior end of the body that are smaller than the gnathopods and are used to grasp the substrate (photo). The abdomen is tiny and attached to the dorsal end of pereonite 7 (photo). This species (Caprella kennerlyi) has two forward-projecting spines on the back of its cephalon (head) (photo) (photo). The articles of the peduncle of antenna 1 are much longer than wide (photo) (photo), and the flagellum of the first antenna is shorter than the peduncle (see photo above and below). On males, the peduncle of antenna 1 is stout and setose (photo) and the flagellum has less than 20 articles. The mandible of this species has a molar process but does not have a palp. Usually the cephalon is fused to the first segment (pereonite) of the pereon. The merus of gnathopod 2 has a sharp, spiny anteroventral projection or a stout, spinelike seta (photo). The propodus of gnathopod 2 is less than 2/3 as wide as long (photo), and the second pereonite does not have a ventral spine between the two gnathopods (photo). Pereonites 1 and 2 of males are more than twice as long as wide (photo). It has gills only on pereonites 3 and 4 (See photos above and below). Pereonites 3 and 4 also have several pairs of spines and have oostegites on mature females, but not even rudimentary legs on either sex. Pereopods 5-7 (the legs near the back) have a single grasping spine or tooth on their propodus (photo photo). Females have a rough texture, with spines on all segments. Often has pink spots and bands.
How to Distinguish from Similar Species: This is an unusually large skeleton shrimp species. Metacaprella anomala has the flagellum of antenna 1 longer than the peduncle and pereonites 1 and 2 of males are not more than twice as long as wide.
Geographical Range: All along the N American Pacific coast
Depth Range: Intertidal and subtidal
Habitat: Many different substrates and fouling communities (first described from a fouling community on a ship in Port Townsend). Often in Abietenaria hydroid colonies.
History: May be
especially well-camouflaged on Plumularia
lagenifera hydroids. The setae
on the antennae
are apparently used to scrape algae off the body. Filter
and detritus eaters such as this species scrape their body
Carnivorous predator and scavenger species allow algae to grow on them,
presumably to increase their camouflage.
Kozloff, 1987, 1996 (as Metacaprella kennerlyi)
Caine, E.A., 1980. Ecology of two littoral species of caprellids (Crustacea) from Washington, USA. Marine Biology 56: pp 327-335
Jensen, M.P., 1969. The ecology and taxonomy of the Caprellidae (Order: Amphipoda; Suborder: Caprellidea) of the Coos Bay, Oregon, area. Ph.D. dissertation, Department of Entomology, University of Minnesota
Martin, D.M., 1977. A survey of the family
Amphipoda) from selected sites along the northern California
Bulletin of the Southern California Academy of Sciences 76: pp 146-167
General Notes and Observations: Locations, abundances, unusual behaviors:
Authors and Editors
Salish Sea Invertebrates web site provided courtesy of Walla