Milne-Edwards, 1830
Hyperiid amphipods are characterised by short, sometimes slender, but typically fat or swollen bodies. The head is very deep, rounded and almost globular, with large, often strikingly coloured eyes, occupying the whole of the two sides of the head. The pereion is often deep, rounded laterally and dorsally and somewhat compressed laterally; the pleon is usually slender and the urosome well developed, often elongate. Marked sexual dimorphism occurs: the male has elongate, slender antennae (a1), while in the female both pairs of antennae are very short.
The maxilliped lacks a palp. Gnathopods are poorly developed and differ between the sexes; pereiopods 3 to 7 are typically slender and in all pereiopods the coxa is very small and sometimes absent. Pleopods are well developed, often powerful. Uropods are laminar, biramous and lack spines.
Larval development is epimorphic and usually lacks a postlarval stage. The life cycle is holoplanktonic.
Ecology
The Hyperiidea are exclusively marine, pelagic and live associated with other zooplankton, in particular Salpida, medusae of Scyphozoa, Siphonophora, and Ctenophora. They may be commensal or parasitic.
Distribution in the North Sea
The pelagic Suborder Hyperiidea is known with eight species in the area, mostly occurring on hosts in the Northern North Sea as guests from the adjacent NE Atlantic waters.
[Description after Isaac et al., 1990]
Key
A picture key is not available, hyperiids may be identified with the separate text key in Hyperiidea: key to species or with the same text key that is included in the picture key of the present system at Page 211: Hyperiidea. The following hyperiid species are included:
Suborder Hyperiidea
Family Scinidae
Scina borealis
Family Phronimidae
Phronima sedentaria
Family Hyperiidae
Hyperia galba
Hyperia medusarum
Hyperoche medusarum
Themisto abyssorum
Themisto compressa
Family Tryphanidae
Tryphana malmi