Photoblepharon steinitzi

The first scientific description of the flashlight fish as a distinct phylogenetic group was authored in 1973 by ichthyologists Tokiharu Abe and Yata Haneda. In this paper, it was assigned subspecific status as P. palpebratus steinitzi.[1] Due to morphological differences and the geographic distance between collection of specimens, it was reclassified as its own species in 1987 by John E. McCosker.[2] Its generic name comes from Greek: "photo" meaning "light" and "blepharon" meaning "eyelash."[3]

The flashlight fish is one of the more derived members of Anomalopidae. It shares reflective lateral line scales with P. palpebratum, Kryptophaneron, and Phthanophaneron. These scales are enlarged in Kryptophanaraon and Photoblepharon, indicating that they are a unique synapomorphy of the two. Refinment of the shutter mechanism down the cladogram is further confirmation of its placement of genera.[4]

The flashlight fish has a short, stout, darkly colored body. Its blunt snout and large eyes are characteristic of anomalopids. Its pectoral fins are preceded by a white splotch, and its preopercle may have a light spot of discoloration, though this is not always the case. A small or absent discoloration of the preopercle distinguishes it from P. palpebratum, which has a larger and bolder white spot. A line of reflective scales run the length of its body from the operculum to the caudal fins. The light organs beneath its eyes are white, but emit a blue-green light in the dark. The fish also possesses black lids that can slide up to cover the bioluminescent organs. The maximum recorded length for this species is 11.0 cm (4.3 in) TL.[2][3]

The flashlight fish has a wide range across the western Indian Ocean and the Red Sea. With a latitudinal range between 21°S and 45°N, it has been collected from various islands, including Réunion and Comoros, to as far east as Maldives, as well as north to Somalia, Oman,[3] Israel, and Egypt.[2] Its typical habitat has a water temperature of 26 °C (79 °F) and a salinity of 35 PSU.[5] It is typically found in and around coelacanth caves[3] up to 60 m (200 ft) in depth during the day.[5] At night it large groups can be seen around coral reefs 3–20 m (9.8–65.6 ft) in depth.[3]

The flashlight fish is a nocturnal predator. It hides in caves and rock crevices during the day and emerges at night to feed. It forms large schools of up to a hundred individuals, the combined light from which can illuminate large areas of reef. Its lights help to both attract and reveal hidden prey, usually crustaceans in the water column. In addition to helping the fish search for food, its light organs also allow the flashlight fish to communicate with other members of its species and evade predators. Mated flashlight fish pairs will ward off other flashlight fish encroaching on their territory by shutting off their lights, swimming nearly on top of the offending fish, and then turning the lights on again to scare it away. Flashlight fish's light organs also serve as a means of evasion. When disturbed or threatened, or when swimming over an open area, individuals will use an erratic "blink-and-run" pattern of swimming slowly in one direction with their lights on, shutting off their lights, darting away in an unpredictable direction, and then blinking their lights rapidly on and off.[6] Little else is known about the biology of this fish.

• Data related to Photoblepharon steinitzi at Wikispecies