A micrograph of an adult male of the cladoceran "Daphnia magna", highlighting the first antenna, a diagnostic character much reduced in females of the same species. Note also the absence of a brood chamber, the short rostrum, and reinforced superior edge of the carapace. This individual measured 1.8 mm in length, and the micrograph was taken with an Olympus BH-2 microscope using bright-field illumination.