Stoplight loosejaw
genus of fishes
The stoplight loosejaws are small, deep-sea dragonfishes of the genus Malacosteus, classified either within the subfamily Malacosteinae of the family Stomiidae, or in the separate family Malacosteidae. They are found worldwide, outside of the Arctic and Subantarctic, in the mesopelagic and bathypelagic zones, below a depth of 500 meters (1,600 feet). This genus once contained three nominal species: M. niger (the type), M. choristodactylus, and M. danae, with the validity of the latter two species being challenged by different authors at various times. In 2007, Kenaley examined over 450 stoplight loosejaw specimens and revised the genus to contain two species, M. niger and the new M. australis.
Malacosteus and the related genera Aristostomias, Chirostomias and Pachystomias are the only fishes that produce red bioluminescence. As most of their prey organisms are not capable of perceiving light at those wavelengths, this allows Malacosteus to hunt with an essentially invisible beam of light. Furthermore, Malacosteus is unique amongst animals in using a chlorophyll derivative to perceive red light. The name Malacosteus is derived from the Greek malakos meaning "soft" and osteon meaning "bone". Another common name for these fishes is "rat-trap fish", from the unusual open structure of their jaws.
Species
There are currently two recognized species in this genus:
Malacosteus australis Kenaley, 2007 (Southern stoplight loosejaw)
Malacosteus niger Ayres, 1848 (Stoplight loosejaw)
Distribution and habitat
These fishes have a wide distribution in all oceans: M. niger is found between 66° N and 33° S, except for the Mediterranean Sea, while M. australis is found in the southern transition zone between 25° and 45° S, where it is bound by the Antarctic Circumpolar Current.
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Datasets, specimens, observations and peer-reviewed methods provide the appropriate test for the technical claims summarized here. The source revision retrieved here is dated Mar 23, 2026. The linked authority identifier is Q134546. None of the 0 selected statements returned an explicit reference. The first chronological checks are 2007 and 1848.
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This entry incorporates text from “Stoplight loosejaw” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.