a suborder of branchiopod crustaceans. They have a pair of large second antennae, which consist of two branches and serve as organs of motion. The torso is covered with bivalve chitinous shells. An alternation of sexual and asexual reproduction, parthenogenesis, is characteristic of the Cladocera. They are from 0.25 to 10 mm long. There are about 380 species. They are largely freshwater animals, living in various bodies of water, from small pools to large lakes. Very few live in the seas. Cladocera serve as food for many fish (smelt, vendace, bleaks, some types of white fish, and others). Certain Cladocera (daphnia) are used as artificially raised food for fish farms and aquariums. Cladocera are good indicators of water pollution, since the majority of Cladocera live in almost clean or slightly polluted reservoirs.