Amphipod

Amphipoda is an order of malacostracan crustaceans characterized by sessile eyes and the absence of a carapace, comprising more than 10,700 species that inhabit nearly all aquatic environments, from freshwater to ocean depths, along with some terrestrial habitats. Most amphipods are marine, though about one-fifth live in freshwater and other non-marine settings, including the family Talitridae's terrestrial landhoppers. They range from less than one millimeter to about 35 centimeters in length and function mainly as detritivores or scavengers within aquatic food webs.