The STOPLIGHT LOOSEJAW is a small, deep-sea dragonfish 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 zone 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 (recorded in New Zealand waters) and the new M. australis.
Malacosteus and the related genera Aristostomias, Chirostomias and Pachystomias are the only fishes that produce RED bioluminescence (hence the 'stoplight' name). Most of their prey organisms are not capable of perceiving light at those wavelengths, allowing 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.
Note the unusual open 'rat-trap' structure of the jaws.
"The sea, once it casts its spell, holds one in its net of wonder forever." - Jacques Cousteau