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Naso lituratus

Orangespine unicornfish

The orangespine unicornfish, known in Italian as pesce unicorno arancione orientale 11, is a Pacific surgeonfish (Acanthuridae) 1 that can reach about 46 cm. 2 It lacks the forehead horn typical of other Naso, but has two orange bony plates, each with a blade, on either side of the base of the tail, and a black dorsal fin. 2 4 It grazes mainly on leafy brown algae, such as Sargassum and Dictyota. 2 6

AcanthuridaeIUCN: Least concern
Naso lituratus

At a glance

Data from the scientific sources listed at the bottom.

Depth in the wild

5–30 m

0 m6 m12 m18 m24 m30 m

Size

up to 46 cm

01020304050

maximum standard length; FAO gives 45 cm total, commonly up to 35 cm

Conservation

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IUCN Red List: least concern (2010). Red List data taken from FishBase and GBIF. 2 10 It does not appear in the CITES lists checked on Species+. 12 In the regional assessment for the Coral Triangle it is listed as Near Threatened (NT). 9 It is caught with nets, traps and spearguns and sold fresh. 4

Where it lives

Red SeaWestern Indian OceanEastern Indian OceanCentral Indo-PacificWestern PacificCentral PacificEastern PacificWestern AtlanticEastern AtlanticMediterranean

From Christmas Island, in the eastern Indian Ocean, across the Pacific: north to Honshu, south to the Great Barrier Reef and New Caledonia, east to Hawaii, French Polynesia and Pitcairn, with a presence also at Clipperton, in the eastern Pacific. 2 It does not live in the western Indian Ocean or the Red Sea: that population is now the separate species Naso elegans. 2 The 2001 FAO guide still treated them as a single species. 4

How to recognise it

Tap a number on the photo: the key explains what to look for.

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  1. 1Orange plates two on each side, at the base of the tail, with the blade pointing forwards in adults 2 4
  2. 2Black dorsal fin a Pacific feature: in Naso elegans it is mostly yellow 4 5
  3. 3Yellow patch above and behind the eye 4 5
  4. 4Orange lips the snout is crossed by a dark band 4 5
  5. 5Tail filaments long and black, they develop in adult males 4

Life in the wild

Where it is found

Areas with coral, rock or rubble, both in lagoons and on the outer side of the reef. 2 Juveniles stay on shallow rocky bottoms. 2 It usually lives between 5 and 30 m; FishBase and Reef Life Survey give an overall range of 0-90 m. 2 5 In Reef Life Survey counts it was observed in the sea between 22.9 and 31.2 °C. 5

What it eats

It grazes on leafy brown algae, mainly Sargassum and Dictyota. 2 4 On a reef in Fiji, in trials with algae placed in the sea, it mainly bit four brown algae (including Sargassum polycystum and Padina boryana) and avoided some green and red algae; chemical extracts of two of these, spread on a favoured alga, were enough to keep it away. 6

Behaviour

The sources describe it as solitary or in small groups, sometimes in large gatherings; juveniles may mix with other surgeonfish of similar size. 2 4 It can turn entirely pale bluish grey, for example at cleaning stations, and during courtship males instantly display a bluish-white area on the nape and narrow pale bars. 2

Reproduction

Separate sexes and external fertilisation; it scatters its eggs in the water and does not care for its young. 3 It probably spawns in pairs, and pair spawning has been observed. 2 3 FishBase also reports spawning aggregations. 3

In the aquarium

From the experience of the BallingMania community.

Community rating
Swimming level
lowmediumhigh
Coral compatibility
lowmediumhigh
Aggression
lowmediumhigh
Care difficulty
lowmediumhigh
Original sheet

A fish from the Indo-Pacific and the Red Sea, where it swims, in pairs or alone, along the deeper waters of coral reefs. In the wild, specimens of about 50 cm in length have been observed, but in the aquarium it does not exceed 25/30. It should be noted that adult specimens have a brighter livery than juveniles. This Acanthurid adapts easily to tanks of about 120 cm in length and 400 litres in volume fitted with rocks colonised by algae, but it can prove aggressive towards specimens of the same species. Adult specimens show some difficulty during acclimatisation, while young ones adapt quickly.

In particular, they may refuse food for as long as about 10/15 days, especially when they are introduced into tanks with greedier fish.

During acclimatisation this fish feeds mainly on fresh algae, such as blanched lettuce and spinach, but it does not refuse adult Artemia, mysis, chironomus and finely chopped mussel flesh. Later on it will willingly accept dried algae (Nori seaweed) and flake and/or granular foods.

photo by: Marco Tironi

Did you know?

Its gut hosts giant bacteria similar to Epulopiscium: in fish collected in Hawaii, some of these bacteria form spores at night, as a normal part of their daily cycle. 7
At Christmas and Cocos Islands, where Indian Ocean and Pacific faunas meet, hybrids with Naso elegans have been found. 8
FishBase lists it as a species poisonous to humans and reports that it is only very rarely toxic. 2

Sources

  1. Froese R., Pauly D. (eds.), via WoRMS (2026). Naso lituratus (Forster, 1801). World Register of Marine Species.
  2. Froese R., Pauly D. (eds.) (2026). Naso lituratus, Orangespine unicornfish. FishBase.
  3. Froese R., Pauly D. (eds.) (2026). Reproduction of Naso lituratus. FishBase.
  4. Randall J.E., in Carpenter K.E., Niem V.H. (eds.) (2001). Acanthuridae. The living marine resources of the Western Central Pacific, vol. 6. FAO.
  5. Reef Life Survey (2026). Naso lituratus, Orange spine unicornfish. Reef Life Survey.
  6. Rasher D.B., Hoey A.S., Hay M.E. (2013). Consumer diversity interacts with prey defenses to drive ecosystem function. Ecology.
  7. Flint J.F., Drzymalski D., Montgomery W.L., Southam G., Angert E.R. (2005). Nocturnal production of endospores in natural populations of Epulopiscium-like surgeonfish symbionts. Journal of Bacteriology.
  8. Hobbs J.P., Frisch A.J., Allen G.R., Van Herwerden L. (2009). Marine hybrid hotspot at Indo-Pacific biogeographic border. Biology Letters.
  9. Comeros-Raynal M.T., Choat J.H., Polidoro B.A., Clements K.D. et al. (2012). The likelihood of extinction of iconic and dominant herbivores and detritivores of coral reefs: the parrotfishes and surgeonfishes. PLoS ONE.
  10. GBIF Secretariat (2026). Naso lituratus, IUCN Red List category. GBIF.
  11. GBIF Secretariat, da Catalogue of Life (2026). Naso lituratus, nomi comuni. GBIF.
  12. UNEP-WCMC, Segretariato CITES (2026). Search for Naso lituratus in the CITES lists. Species+.

Sources checked on 5 November 2026. Community texts and ratings are kept separate from the scientific data.

Download the original sheet (Italian)All species