Leiognathidae

Leiognathidae, the ponyfishes, slipmouths or slimys / slimies, are a small family of fishes in the order Perciformes.[2] They inhabit marine and brackish waters in the Indian and West Pacific Oceans. They can be used in the preparation of bagoong.

Leiognathidae Temporal range: 56–0 Ma PreЄ Є O S D C P T J K Pg N Eocene to Present[1]
Eubleekeria splendens
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Perciformes
Family:	Leiognathidae T. N. Gill, 1893
Genera[2]
Aurigequula Equulites Eubleekeria Gazza Karalla Leiognathus Nuchequula Photolateralis [3] Photopectoralis Secutor

Ponyfishes are small and laterally compressed in shape, with a bland, silvery colouration. They are distinguished by highly extensible mouths, and the presence of a mechanism for locking the spines in the dorsal and anal fins. They also possess a highly integrated light organ in their throats that houses symbiotic bioluminescent bacteria that project light through the animal's underside.[4][5][6] Typically, the harbored bacterium is only Photobacterium leiognathi, but in the two ponyfish species Photopectoralis panayensis and Photopectoralis bindus, Photobacterium mandapamensis is also present.[7] Two of the most widely studied uses for luminescence in ponyfish are camouflage by ventral counterillumination[8][9] and species-specific sexual dimorphism.[5][6][10][11]

Although ponyfish seem quite ordinary and morphologically similar, their light organ systems are highly variable across species and often between sexes.[10][11]