অর্থ : 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.

অর্থ : Minute freshwater crustacean having a round body enclosed in a transparent shell. Moves about like a flea by means of hairy branched antennae.