Length: 5-22mm. Head and body smooth dorsally except pereonite 5 may have paired spines; laterally large anteriorly pointing spines at the bases of gnathopod 2, antero-lateral spines on pereonites 3 and 4; pereonite 5 distinctly sculptured anteriorly, giving the appearance of large lateral spines. Distinct lateral spine between insertions of gnathopod 2. Antenna 1 as long as cephalon plus pereonite 2; antenna 2 shorter than the two basal articles of antenna 1. Gnathopod 1 with barely serrate grasping margin to propodus and dactylus. Gnathopod 2 attached posterior to median of pereonite 2; basis with antero-lateral ridge ending in a spine-like process; propodus with proximal grasping spine, distal ‘tooth’, groove and triangular projection. Gills large, oval. Pereopods 5 - 7 increasing in length; propodus with proximal grasping spines, palm slightly concave and bearing a few spines. Female differs in antenna 2 equal in length to peduncle of antenna 1; gnathopod 2 attached anteriorly on pereonite 2 and having a longer basis.
World-wide (may be species complex)
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.
Most common in intertidal + shallow waters on seaweeds, hydroids, gorgonians, bryozoans, and ascidians, artificial structures: wharf pilings, aquaculture structures and marina floats. Found down to 3000 m (Schellenberg 1926).
Variations described within range, but thus far no taxonomic decision has been reached on these. Parts of distribution likely due to ship associated introductions
National Museum of Natural History, Washington DC: (NMNH) 113619* (C. aequilibra); (NMNH) 39409; Near Port Royal , South Carolina; (NMNH) 258977
Caprella equilibra is a species of skeleton shrimp in the family Caprellidae. It lives among other organisms on the seabed and occurs in both shallow and deep water in many parts of the world.
The skeleton prawn is not closely related to other amphipods. A cephalothorax results from the head's partial fusion with the first and second thoracic segments. The body is slender, cylindrical, elongate and unflattened. The first and second thoracic segments bear maxillipeds and gnathopods (feeding appendages) respectively, the third bears gnathopods, and the sixth, seventh and eighth bear well-developed periopods (walking legs). The remaining thoracic segments and the small abdominal segments bear vestigial appendages. The tips of some of the appendages have grasping hooks to cling onto the substrate.[2] The male Caprella equilibra is about 22 mm (0.9 in) long while the female is about half that size.[3]
C. equilibra has a cosmopolitan distribution. The type locality is the United States, where it is present on both coasts, and the range includes Argentina, Australia, Japan, Madagascar, Malaysia, New Zealand, the Philippines, South Africa, West Africa, Western Europe and Venezuela. Its depth range is from the surface down to about 3,000 m (10,000 ft). Its typical habitats include living concealed among seagrasses, sponges, green and red algae, hydroids, octocorals, bryozoans and colonial tunicates.[3]
This species lives on the seabed, moving much like a looping caterpillar: gripping with its front limbs, bending its body and drawing in its rear limbs, then releasing its front limbs and extending its body.[2] It is mainly a detritivore but has a more varied diet than some other caprellids, ingesting some of the hydroids to which it clings and even feeding on the plankton collected by the polyps.[4]
Caprella equilibra is a species of skeleton shrimp in the family Caprellidae. It lives among other organisms on the seabed and occurs in both shallow and deep water in many parts of the world.
