Juvenile Harlequin Filefish (Oxymonacanthus longirostris) captured from the Monte Bello Islands off WA's Pilbara coastline in 2015. (Photo Credit: Sue Morrison)

Harlequin Filefish

Oxymonacanthus longirostris

A charismatic, although infrequently encountered, fish with a striking colour pattern of bright yellow-orange spots on a blue-green background. Fins mostly yellowish except for the blackish pelvic fin rudiment and a black spot on the caudal fin.

Morphology

The shallow body depth, elongated snout and vivid colour pattern (described above) make this species unmistakable. Grows to a maximum size of 12 cm.

Evolution

Only two species are currently known in the genus Oxymonacanthus, which is part of the Family Monacanthidae, a group more commonly known as Leatherjackets or Filefishes. These fishes are so named for their tough, leathery skin which has a sandpaper-like feel due to the presence of a dense covering of tiny spines.

Behaviour

Feeds exclusively on the polyps of Acropora corals, a mode of feeding for which the species has evolved its elongated, tubular snout. Population declines linked to coral bleaching. Lives in monagomous pairs (see reproduction notes below).

Method of reproduction

Sexual; forms exclusive monogamous pairs and spawns amongst dead coral often on algae.

Habitat

Marine

Shallow reefs with Acropora coral growth, between 1-35 m depth.

Distribution

Throughout tropical parts of the Indo-West Pacific region from East Africa to Tonga, including coastal and offshore reefs of north-western Australia and the Great Barrier Reef.

Life Cycle

Oviparous

Taxonomy

Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Tetraodontiformes
Family: Monacanthidae
Genus: Oxymonacanthus
Species: longirostris
Name Published Year: 1801
Scientific Name Authorship: Bloch & Schneider
Commercial Impact: 

Highly prized in the aquarium trade, with large numbers removed from the wild annually.

Conservation Assessment: Vulnerable

Net Conservation Benefits Fund

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Western Australian Museum Collections https://museum.wa.gov.au/online-collections/names/Oxymonacanthus-longirostris
Accessed 30 Aug 2023

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