Ornate angelfish

Lore & Background

Genicanthus bellus was first formally described in 1979 by American ichthyologist John Ernest Randall, with the type locality given as outside the barrier reef off District of Paea, Tahiti, at a depth of 60 meters. The specific name bellus means 'beautiful'. The species is known to hybridise only with the blackstriped angelfish (Genicanthus lamarck).

Females and juveniles have a greyish to bluish background with wide black bands and a blue longitudinal stripe on the lower flanks. Males are pale bluish to greyish with horizontal golden stripes along the centre of the flanks and lower back; their caudal fins are unpigmented, often with orange patches, and have filamentous extensions that are bright blue. The lips are also bright blue in males. Females have a black stripe running vertically from the nape through the eye, and additional black stripes with white or pale blue margins. The dorsal fin contains 15 spines and 15–16 soft rays, while the anal fin has 3 spines and 16–17 soft rays.

The species is found at depths between 25 and 100 meters on deep reefs, often in areas swept by strong currents on outer drop-offs. It is sociable, living in schools with harems of 3–7 fish, and its mating system has been described as more like lekking. All angelfish are sequential protogynous hermaphrodites: newly adult fish are female, but dominant females can change sex to male in as short a time as a fortnight in the absence of a male. They feed mainly on plankton, forming shoals in midwater, and also on benthic invertebrates such as polychaetes and bryozoans, as well as algae.

Reader's Guide

The ornate angelfish is very infrequent in the aquarium trade and fetches high prices because it is rarely collected due to the depths at which it lives. It is sometimes more numerous in the trade when collecting effort is increased. There can be high mortality in specimens collected for the trade, but healthy, acclimated fish can be very hardy and resilient in captivity. Its wide but localised distribution in the western Pacific Ocean and eastern Indian Ocean—including records from Tahiti, Guam, Palau, Tonga, the Cook Islands, the Marshall Islands, the Philippines, southern Japan, southern Indonesia, and Australian waters such as the Cocos (Keeling) Islands, Christmas Island, and Holmes Reef in the Coral Sea—suggests that its preference for quite deep water may mean the species is under-recorded. The species' striking colour differences between sexes and its lek-like social structure make it a notable subject for studies of reef fish behaviour and hermaphroditism. Its hybridisation only with Genicanthus lamarck further highlights its distinct evolutionary relationships within the genus.

Did You Know?

• Males have bright blue lips and filamentous caudal fin extensions with orange patches.
• Females and juveniles have a black stripe that runs vertically from the nape through the eye.
• The species is a sequential protogynous hermaphrodite; a dominant female can change sex to male in as little as a fortnight.