NASO ANNULATUS - (QUOY & GAIMARD, 1825)
Picture courtesy of: Yves Thévenet
Nason à bordures blanches, Short-horned unicorn-fish, Ringtailed unicornfish, White margin unicornfish, White-margin unicorn, Whitemargin unicornfish, Witrand-eenhoringvis, Hvidkantet næsehornsfisk, Weißband-Nashornfisch, Rufia anelar, Hime-tenguhagi, ヒメテングハギ, 环纹鼻鱼, 剥皮仔, 環紋鼻魚, Cá một sừng sọc, أبو قرن, تک شاخ ماهی سفید,
Synonymes
Acanthurus incipiens (Jenkins, 1903)
Naso herrei (Smith, 1966)
Naseus marginatus (Valenciennes, 1835)
Priodon annularis (Valenciennes, 1835)
Priodon annulatus (Quoy & Gaimard, 1825)
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Description
Dorsal spines (total): 5; Dorsal soft rays (total): 28-29; Anal spines: 2; Anal soft rays: 27-28; Pectoral fins rays: 17-19; Pelvic fins rays I, 3; Body depth about 2.2 in SL of subadults to about 2.8 in SL in large adults. The body of the Ringtail Unicornfish tapers to a narrow caudal peduncle. There are two scutes on the caudal peduncle, each bearing a strong keel. When fish are about 20 cm in length a long horn develops from a bump anterior to the eye. The horn of mature fish can be as long as the head. The species is brown to grey or blackish. Juveniles often have a white ring around the caudal peduncle. The caudal fin margin and membranes of adults are white. subadults with black caudal rays, narrow margins and white caudal filaments; pectoral fins with white distal margins. Max length: 100.0 cm TL. Depth range: 1 - 60 m, usually: 25 - 60 m.
Etymology
Naso: from Latin, nasus = nose.
annulatus: from Latin, annulus = ring.
Original description: Priodon annulatus Quoy & Gaimard, 1825 - Type locality: Timor Island, southern Malay Archipelago, Timor Sea, eastern Indian Ocean.
Distribution
Red Sea, Indo-Pacific: East Africa, Oman, Madagascar, Seychelles and Mascarenes east to Hawaiian Islands, Marquesas Islands and Gambier Islands, north to southern Japan, south to Western Australia, Queensland (Australia), New Caledonia, Lord Howe Island, Norfolk Island, and Tonga; Clipperton Island.
Biology
Juveniles occur in clear, shallow lagoon reefs at depths as little as 1 m; adults rarely seen in less than 25 m, encountered off outer reef drop-offs in small schools. Benthopelagic. Feeds on large zooplankton during the day and shelter within the reef during the night; also benthic algae. Spawn in pairs. Reports of ciguatera poisoning.
Similar species
Naso brachycentron (Valenciennes, 1835) - Reported from New Caledonia. Distinctive humped back; horn only in adult males. A few scattered small dark-edged pale spots on postorbital head and body above pectoral fins. No white margin posteriorly on caudal fin.
Naso brevirostris (Cuvier, 1929) - Reported from New Caledonia - Link to the species (here). Adults bluish grey to olivaceous brown in color, commonly pale anteriorly and on cheek and throat.