[1][2][3] It and the glasshead barreleye fish are the only vertebrates known to employ a mirror, in addition to a lens, to focus an image in its eyes.
[4][5] This species probably has a worldwide tropical and temperate distribution; in the Atlantic Ocean it is known from Bermuda, the Bahamas, the Greater Antilles, and the Gulf of Mexico, and in the Pacific Ocean it is known from the California Current region and the South China Sea.
[6] The eyes are cylindrical and face upward, with an accessory outgrowth to the side, and are covered with a silvery layer called the "argentea" for camouflage.
[3] The diet of D. longipes consists primarily of copepods and other small crustaceans, though as food is scarce in the deep sea it may take anything it can catch.
The pectoral and pelvic fins form early, as does the stomach on the left side.
However, inside the diverticulum the light is reflected and focused onto the retina by a curved composite mirror derived from the retinal tapetum, composed of many layers of small reflective plates possibly made of guanine crystals, acting as the reflector equivalent of a Fresnel lens.