views updated

Amphipoda (sandhoppers, beach hoppers, beach fleas, water lice; phylum Arthropoda, subphylum Crustacea, superorder Peracarida) Order of mainly laterally compressed crustaceans, with the cephalothorax devoid of a carapace and the whole head fused to one thoracic segment, or occasionally to two. The first three pleopods are usually many-segmented swimmerets, the posterior ones modified for jumping and comprising a few segments. The gills are borne on the thoracopods. There are 4000 species.