Common name: Pony Fishes, Ponyfishes, Silverbellies, Slipmouths



Small silvery compressed fishes with highly protrusible mouths. 

All species are bioluminescent, with a colony of Photobacterium, bioluminescent bacteria, housed in a ring-like organ around the oesophagus. Males have larger light organs than females, presumably for courtship.

Ponyfishes also have a unique locking mechanism in both their dorsal and anal-fin spines. Most species are less than 20 cm in length.

They are widespread throughout tropical waters of the Indo-West Pacific where they live on soft bottoms in coastal marine and estuarine waters.

Cite this page as:
Dianne J. Bray, Ponyfishes, LEIOGNATHIDAE in Fishes of Australia, accessed 17 Jun 2024,

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Family Taxonomy

The Leiognathidae comprises about 50 species in 11 genera; 19 described species in 7 genera occur in Australian waters.

Family Distribution

Ponyfishes are found over soft bottoms in coastal marine and estuarine environments, often out over the continental shelf to depths of around 150 m. They are nocturnal, swimming in midwater at night, and demersal during the day. Leiognathids are distinctive in having a silvery body which is markedly compressed.

Family Description

Meristic features: Dorsal fin VII-IX, 15-17; Anal fin III, 13-15; Pectoral fin ; Pelvic fin I, 5; Caudal fin ; Vertebae 24 (10+14); Branchiostegal rays 5.

Ponyfishes have a unique locking mechanism on some of their dorsal and anal-fin spines.

Family Size

Maximum length is 28 cm.

Family Reproduction

Many species are strongly sexually dimorphic, whereby the light organ and other associated features are larger in males than in females. This allows them to intensify the light produced during courtship. Males of some species also have transparent patches on the sides, pectoral, buccal, or gular regions that concentrates light on their bodies.


Dianne J. Bray


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