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Naso annulatus (Quoy &. Gaimard, 1825)
Ring-tailed Unicorn-fish; Ring-tailed Unicornfish; Ringtailed Unicornfish; Short-horned Unicorn-fish; White-margin Unicorn; Whitemargin Unicornfish; Priodon annulatus Quoy and Gaimard, 1825; White-margin unicornfish

Life   Vertebrata   Fish   Acanthuridae   Naso

Naso annulatus
© Copyright John Rangall, 2006 · 0
Naso annulatus

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Main identification features
  • horn very long
  • blue-grey
  • tail fin black + pale membranes and edges
  • tail base: 2 keels
Body elongate, oval; snout pointed, slopes at about 60°; adult with long, tapering horn before eye that can extend 1 head length forward (a bump on forehead of juveniles); teeth small, conical, with tips slightly depressed, smooth or with slight denticulations; 2 pairs of cutting keels on plates on narrow tail base; pelvics I, 3; tail edge straight, a series of small scallops on rear margin, long filaments from top and bottom in males (straight in juveniles); dorsal VI, 28-29; anal II, 27-28; pectoral 17-19 rays.

Uniform olive to brown; can switch on pale blue color; tail with wide rays blackish, membranes between rays, narrow margin, and filaments white. Juveniles with thin white dorsal and anal margins, a white saddle on the caudal peduncle, tail dark with white margin.

Size: 100 cm.

Habitat: juveniles and subadults benthic on reefs and rocky shores, adults in open water near exposed reef fronts.

Depth: 0-122 m; subadults usually 5-15 m, adults usually 10-30 m.

An Indo-Pacific species recorded as a vagrant from Cocos and Clipperton Atoll.

Abundance: Common.
Cites: Not listed.
Climate Zone: Equatorial (Costa Rica to Ecuador + Galapagos, Clipperton, Cocos, Malpelo).
Depth Range Max: 122 m.
Depth Range Min: 0 m.
Diet: pelagic fish larvae; zooplankton; benthic microalgae.
Eastern Pacific Range: Northern limit=11; Southern limit=6; Western limit=-110; Eastern limit=-87; Latitudinal range=5; Longitudinal range=23.
Egg Type: Pelagic; Pelagic larva.
Feeding Group: Omnivore; Planktivore.
FishBase Habitat: Reef Associated.
Global Endemism: All Pacific (West + Central + East); Indo-Pacific only (Indian + Pacific Oceans); TEP non-endemic; "Transpacific" (East + Central &/or West Pacific); All species.
Habitat: Corals; Reef associated (reef + edges-water column & soft bottom); Rocks; Reef (rock &/or coral); Reef only.
Inshore Offshore: Inshore; Inshore Only.
IUCN Red List: Not evaluated / Listed.
Length Max: 100 cm.
Regional Endemism: Island (s) only; Island (s); Tropical Eastern Pacific (TEP) non-endemic; Eastern Pacific non-endemic; All species.
Residency: Vagrant.
Salinity: Marine; Marine Only.
Water Column Position: Bottom; Mid Water; Near Bottom; Bottom + water column;

Scientific source:

Links to other sites

  • Allen , G.R. and Robertson, D.R., 1997., An Annotated Checklist of the fishes of Clipperton Atoll, Tropical Eastern Pacific., Revista de Biologia Tropical, 45:813-843.
  • Osburn , R. C. and Nichols, J. T., 1916., Shore Fishes Collected by the 'Albatross' Expedition in Lower California with Descriptions of New Species., Bull. Amer. Mus. Nat. Hist., 35:139-181.
  • Quoy , J. R. C. and Gaimard, J. P., 1824., Description des Poissons. Chapter IX. In: Freycinet, L. de, Voyage autour du Monde...exécuté sur les corvettes de L. M. "L'Uranie" et "La Physicienne," pendant les années 1817, 1818, 1819 et 1820. Paris., Voyage Uranie, Zool., :1-328.
  • Robertson , D.R. and Allen, G.A., 1996., Zoogeography of the shorefish fauna of Clipperton Atoll., Coral Reefs, 15:121-131.
  • Smith , M. M. and Heemstra, P., 1986., Smith's Sea Fishes. Johannesburg: Macmillan South Africa. 1047 pp., Macmillan South Africa:1047pp.


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