Malacosteus niger

Description

Malacosteus niger is a species of fish in the family Stomiidae, the barbeled dragonfishes. It is known by the common names northern stoplight loosejaw, lightless loosejaw, black loosejaw, and black hinged-head. It lives in oceans around the world from tropical to subarctic waters. The postorbital photophore in this species is larger than in M. australis. It also differs in lateral photophore count, as well as in morphological characters. The maximum known length is 25.6 cm (10.1 in). Its specific epithet niger is Latin for "black". M. niger occurs in the mesopelagic zone of all oceans. Contrary to barbeled dragonfishes in general, it is not a vertical migrator. While the morphology of M. niger with huge fangs and an enormous gape is typical for its family and suggests adaptations to piscivory, its diet in fact contains a substantial proportion of zooplankton. It is suggested that its dominant feeding mode is searching for zooplanktonic prey (copepods in particular) using bioluminescence to illuminate a small search area, with infrequent encounters with larger prey items. The likely origin of the pigment necessary for detecting its long wavelength bioluminescence, a chlorophyll derivative, is the copepods themselves.