WHAT ARE AMPHIPODS ?
Amphipod crustaceans are peracarid crustaceans, typically ranging in size from 2 to 50 mm, although a few may be larger. Amphipods are common in aquatic ecosystems throughout many parts of the world, inhabiting marine, brackish, and freshwater environments. A few species also live in terrestrial ecosystems. The order Amphipoda, which contains nearly 7,000 described species, is divided into three and sometimes four suborders: Gammaridea, Caprellidea, Hyperiidea, and Ingolfiellidea. The latter, however, are probably highly specialized gammarideans and therefore do not merit recognition as a suborder.
Gammaridea, with more than 5500 described species, is not only the largest amphipod suborder but also contains all of the freshwater and subterranean taxa. Approximately 21 superfamily groups, 95 families (or family groups) and more than 1000 genera are recognized within this suborder.
Crangonyx barri Zhang & Holsinger (ca. 8.0 mm long), a stygobitic amphipod from Mammoth Cave System, Kentucky, USA (Photograph by Chip Clark)
A BRIEF LOOK AT THE WAY AMPHIPODS ARE
CLASSIFIED:
Phylum Arthropoda
Subphylum Crustacea
Class Malacostraca
Superorder Peracarida
Order Amphipoda
Suborders
Caprellidea
Hyperiidea
Gammaridea (including ingolfiellids)
TAXONOMIC STRUCTURE
Generalized gammaridean amphipod, illustrating
principal morphological features. 1, head (composed of 6 fused segments) (eye
is degenerate or absent in stygobionts); 2, antenna 1; 3, antenna 2; 4, mouth
parts (mostly hidden, including the upper lip, 1 pair of mandibles, lower lip,
2 pairs of maxillae, and 1 pair of maxillipeds; 5, pereonites 1-7; 6, pereopods
1-7 (1st two are modified as gnathopods); 7, pleonites 1-3 (expanded lateral
margins are called pleonal or epimeral plates); 8, pleopods 1-3; 9, urosomites
1-3; 10, uropods 1-3; 11, telson.