Latreille, 1816
Amphipoda are peracarid crustaceans without a carapace (because secondarily lost). The first thoracomere is fused to the head. Body usually laterally compressed, however, dorso-ventral compression also occurs in Amphipoda. There is one pair of maxillipeds and seven pairs of uniramous pereiopods. The first, second and sometimes other pereiopods also, are frequently modified as chelae or subchelae. The coxae of the pereiopods are expanded as lateral side plates (the so-called coxal plates). In the abdomen two regions are distinguished of three segments each and with typical appendages: the anterior pleon with pleopods and the posterior urosome with uropods. The telson is free or fused with the last somite of the urosome; other somites of the urosome are sometimes fused. The gills are located on the thorax. The eyes are compound and sessile, absent in some, and huge in many (but not all) members of the pelagic Suborder Hyperiidea.
Larval development is epimorphic, usually without a postlarval stage.
The Order Amphiopoda includes four suborders, all but one (*) known from the North Sea.
¥ Suborder Gammaridea (predominantly benthic, some species are occasionally planktonic)
¥ Suborder Caprellidea (benthic or clung to other organisms)
¥ Suborder Hyperiidea (marine, pelagic)
¥ Suborder Ingolfiellidea * (marine, interstitial; also cave dwellers)
Ecology
Amphipoda are free-living or parasitic in marine, brackish-water, freshwater and even moist terrestrial habitats. Most of the marine amphipods are found in the benthos; less species have taken a pelagic lifestyle, either free-living or associated with other zooplankton. For various reasons some of the benthic amphipods occur also occasionally, and for short time in the pelagic and could get caught during planktonic sampling.
Distribution in the North Sea
The pelagic Suborder Hyperiidea is known with eight species in the area, mostly occurring in the Northern North Sea as guests from the adjacent NE Atlantic waters. At least some 250 benthic species are known from the North Sea, all belonging to the suborders Caprellidea (11 species) and Gammaridea (about 240 species). Benthic amphipods that occasionally occur in the plankton are not included in the present system at species level; we refer to the remarks that are made in the Introduction about the pelagic occurrence of benthic species (see Zooplankton and micronekton).
If benthic amphipods should be found in North Sea plankton samples and their identification to species is required, the references at the bottom of this page are advised (also to be found in the literature field). Otherwise, the following text keys at this and linked pages can be used to identify to suborders or to families. Note that the large Suborder Gammaridea and the much smaller Suborder Caprellidea are not keyed out with respect to the North Sea species. The hyperiid species, however, can be identified with the separate (text) key Hyperiidea: key to species or with the same key at Page 211: Hyperiidea.
Text key to the suborders of the Amphipoda (Ingolfiellidea excluded).
1a. Metasome and urosome well developed; limbs not reduced ---------------------------------- 2
1b. Metasome and urosome reduced and quite rudimentary, with a few, rudimentary limbs ---------
------------------------------------------------------------------ Suborder Caprellidea
2a. Maxillipedes with 1-4 segmented palp -------------------------------- Suborder Gammaridea
2b. Maxillipedes without a palp ------------------------------------------- Suborder Hyperiidea
References for identification
De Kluijver et al., in prep.
Chevreux and Fage, 1925
Lincoln, 1979
Stephensen, 1935-42
[Description after Brusca and Brusca, 1990]
The following amphipod species are included:
Order Amphipoda
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