Photoblepharon steinitzi
The flashlight fish (Photoblepharon steinitzi) is a species of saltwater anomalopid fish of the order Beryciformes. It is native to the western Indian Ocean and the Red Sea where it is found near coral reefs. It is small at only 11.0 cm (4.3 in) in length, and relatively stout compared to other members of its family. It has a mostly solid black body, with the exception of white discoloration around its pectoral fins and a lateral line of reflective scales. It is most notable for the bioluminescent organs located underneath its eyes, which it uses to find prey, evade predators, and communicate with other members of its species. Like other Beryciformes, its reproduction is oviparous. It has little or no commercial value, and this combined with its timid, nocturnal nature makes population sizes and trends unknown. As such, it is listed as Data Deficient by the International Union for the Conservation of Nature.
| Flashlight fish | |
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Not evaluated (IUCN 3.1) | |
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| Species: | P. steinitzi |
| Binomial name | |
| Photoblepharon steinitzi T. Abe & Haneda, 1973 | |
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Photoblepharon palpebratus steinitzi Abe & Haneda, 1973 | |
Taxonomy and phylogeny
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]
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| Phylogenetic tree of Anomalopidae.[4] |
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]
Description
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]
Distribution and habitat
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]
Biology and ecology
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.
References
- Abe, Tokiharu; Yata Haneda (1973). "Description of a new fish of the genus Photoblepharon (family Anomalopidae), from the Red Sea". Ministry of Agriculture Bulletin. 60: 57–62.
- McCosker, John E.; et al. (1987). "Notes on the Biology, Taxonomy, and Distribution of Flashlight Fishes (Beryciformes: Anomalopidae)". Japanese Journal of Ichthyology. 34: 157–164. doi:10.1007/BF02912410.
- Froese, Rainer and Pauly, Daniel, eds. (2017). "Photoblepharon steinitzi" in FishBase. January 2017 version.
- Johnson, G. David; et al. (1988). "Mechanisms of light organ occlusion in flashlight fishes, family Anomalopidae (Teleostei:Beryciformes), and the evolution of the group". Zoological Journal of the Linnean Society. 94: 65–96. doi:10.1111/j.1096-3642.1988.tb00882.x.
- "Photoblepharon steinitzi". eol.org. Encyclopedia of Life. Retrieved 16 January 2017.
- Morin, James G.; et al. (1975). "Light for All Reasons: Versatility in the Behavioral Repertoire of the Flashlight Fish". Science. 190 (4209): 74–76. doi:10.1126/science.190.4209.74.
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