water flea

(noun) minute free-swimming freshwater copepod having a large median eye and pear-shaped body and long antennae used in swimming; important in some food chains and as intermediate hosts of parasitic worms that affect man e.g. Guinea worms. Synonyms: cyclops, water flea.

(noun) minute freshwater crustacean having a round body enclosed in a transparent shell; moves about like a flea by means of hairy branched antennae. Synonyms: daphnia, water flea.