Family OPISTOGNATHIDAE


Common name: Jawfishes, Grinners, Harlequins, Missing Links, Monkeyfish, Pugs, Smiler

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Summary:
Jawfishes (family Opistognathidae) are slender marine fishes with large bulbous heads, large upper jaws, huge mouths and prominent eyes. They have a single long-based dorsal fin, the two outermost pelvic-fin rays are unbranched and thickened, and they usually lack head scales. They are obligate burrow-dwellers, with each individual using its large mouth to excavate and maintain its burrow. Jawfishes are oral egg-brooders, and males incubate the developing eggs inside their large mouths.

Cite this page as:
Dianne J. Bray, Jawfishes, OPISTOGNATHIDAE in Fishes of Australia, accessed 29 May 2017, http://fishesofaustralia.net.au/Home/family/236

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Family Taxonomy

The family Opistognathidae comprises three genera with more than 80 described species. Eighteen described species in two genera are known from Australian waters, and many species are endemic. Jawfishes often live in habitats that are difficult to sample, and new species continue to be found.

Family Distribution

The family is widespread on the continental shelf in tropical and subtropical seas of the Atlantic, Indian and Pacific Oceans. Although most species inhabit burrows in shallow sandy and rubble areas near coral reefs, some live in bays, while others occur in deeper waters to a depth of 375 metres.

Jawfishes use their large mouths to excavate extensive vertical burrows in sandy, rubble or muddy substrates. Some species live in crevices, and others share their burrows with commensal invertebrates. Rarely venturing far, they either prop at the burrow entrance with only their head showing, or hover nearby. They are often seen spitting sand and rubble from their mouths as they extend and maintain their burrows. If threatened they immediately dart tail first into the burrow for protection. Jawfishes are active during daylight hours, and reportedly cover the burrow entrance with a pebble or coral rubble at night.

Family Description

Dorsal fin IX-XII, 10-22; Anal fin II-III, 10-20; Pelvic fin I, 5: Branchiostegal rays 6. 
Body moderately long, slender, compressed; head large, anterior profile strongly convex, eye large, near dorsal surface of head. Mouth large, horizontal, terminal; upper jaw large, protractile, extending well beyond eye; teeth small, present on jaws and vomer, absent from palatines; gill rakers well-developed. Body scales small, cycloid, usually absent from head; lateral line runs high on body to beneath middle of dorsal fin. Dorsal fin long-based, continuous, slightly notched in some; anal fin long-based, low; caudal fin rounded or lanceolate.

Family Size

Although the largest species grows to about 50 cm in length, most are less than 12 cm in length.

Family Feeding

Jawfishes feed on bottom-dwelling and planktonic invertebrates.

Family Reproduction

The sexes are separate, and fertilisation is external. Males perform elaborate courtship displays and some species form monogamous pairs. Females lay their eggs inside the burrow of the male, and following fertilisation, the male broods the eggs inside his mouth until they hatch. Eggs and larvae of several species have been described.

Family Commercial

Although of no interest to fisheries, some species are taken as bycatch in commercial trawls. Several jawfishes are also collected for sale in the aquarium industry.

Family Remarks

Some species have sexually dimorphic jaws, with males having a longer maxilla, and therefore larger mouths than females.

Author

Dianne J. Bray

References


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