What is "amphipoda"

Amphipoda \Am*phip"o*da\, n. pl. [NL., FR. Gr. ? + ?, ? foot.] (Zo["o]l.) A numerous group of fourteen -- footed Crustacea, inhabiting both fresh and salt water. The body is usually compressed laterally, and the anterior pairs or legs are directed downward and forward, but the posterior legs are usually turned upward and backward. The beach flea is an example. See Tetradecapoda and Arthrostraca.

Amphipoda is an order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. Amphipods range in size from and are mostly detritivores or scavengers. There are more than 9,500 amphipod species so far described. They are mostly marine animals, but are found in almost all aquatic environments. Some 1900 species live in fresh water, and the order also includes terrestrial animals and sandhoppers such as Talitrus saltator.