Distribution:
Indo-West Pacific.
Habitat:
Coastal and brackish water, over mud bottoms with poor visibility.
Remarks:
Leiognathid Ponyfishes are a family of slimy, bioluminescent fishes with highly compressed bodies and small scales. Of note is the bacterial light organ, a ring of tissue that surrounds the esophagus and contains the symbiotic bacteria Photobacterium leiognathi. Although this organ is located around the esophagus, light is visible on the flanks because of a transparent patch on each side of the body. The shape of this transparent patch varies from species to species, and even varies within species, between the sexes.
Ponyfishes can control the amount of light emitted from their flanks by use of a series of reflective layers and shutters that are part of the light organ. This allows the fish to flash, diffuse or direct light. In fact, these fishes have been observed to synchronize their light flashes when schooling. While the reason for the light organ is unclear, this synchronized behavior suggests it may serve to avoid predators, attract prey, space individuals within the school, or serve as sex-specific signaling.
The body of the Ponyfish is covered in small scales, however the head is usually naked. The upper surface of the head has several bony ridges. The mouth is small and highly protrusible, and teeth are absent on the palate. In fact, the scientific name Leiognathidae comes from the Greek leio meaning "smooth, flat" and gnathos. meaning "jaw." These fish use their "flat jaws" and protrusible mouths to consume their prey, mainly benthic invertebrates.
Ponyfishes are important to artisanal fisheries.
This family contains 3 genera (Gazza, Leiognathus, and Secutor), with about 30 species.
References:
Nelson 2006;
Sparks et al. 2005