Common name: orangespine unicornfish
Synonyms and Other Names: Synonyms (from Eschmeyer et al. 1998) include: Monoceros ecornis, Prionurus eoume, Prionurus filamentosus, Monoceros garretti, Naseus incornis. Original combination = Acanthurus lituratus.
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Identification: Acanthurids are generally disc-shaped, laterally compressed fishes with one or more spines or keeled bony plates on each side of the caudal peduncle. The dorsal fin is continuous and unnotched. Many species are very colorful.
The orangespine unicornfish has a continuous, unnotched dorsal fin with VI spines and 27-30 soft rays. The anal fin is long, with II spines and 28-30 soft rays. The caudal fin is lunate; adult males develop a long filament from the tip of each lobe. The caudal peduncle bears two forward-directed knife-like plates. These plates are not well-developed in juveniles. The keeled peduncular plates are bright orange. Body color is grey-brown with distinctive black, yellow and white markings (see photo above). The species lacks any anterior protuberance or "horns" along that forehead that are found in some other acanthurids. Summarized from Randall 2001.
Similar species: No Atlantic surgeonfish has an orange spot at the base of the tail. Whitespotted filefish (Cantherhines macrocerus) have orange recurved spines, however, they also have a stout first dorsal spine and orange to brown body color.
Size: to 45 cm (Randall 2001)
Native Range: Throughout the Indo-Pacific from the Red Sea (excepting the Gulf of Oman and Persian Gulf) south to Natal and east to Hawaii and French Polynesia. In the western Pacific from Suruga Bay (Honsu) to the southern Great Barrier Reef (Randall 2001). The Indian Ocean population is recognized as a separate species, Naso elegans (Froese and Pauly 2005).
In Florida, this species has been observed off Boca Raton (in 2000 [Semmens et al 2004, REEF 2008] and in 2001 [REEF 2008]). In April 2018 an individual was spotted and removed from Molasses Reef in the Florida Keys National Marine Sanctuary by REEF personnel. In Georgia, this species was sighted at Gray's Reef National Marine Sanctuary in 2006 (REEF 2008). One fish was sighted for each observation.
Table 1. States with nonindigenous occurrences, the earliest and latest observations in each state, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Naso lituratus are found here.
Table last updated 9/23/2021
† Populations may not be currently present.
Ecology: A shallow-water species, the orangespine unicornfish is found near coral reefs or over rocky bottoms (Allen et al. 2003; Randall 2001). The species feeds on benthic algae, such as Sargassum, Dictyota and Gracilaria (Nelson and Tsutsui 1981; Myers 1999; Randall 2001). In Micronesia, both males and female reach maturity at approximately two years old (females 15 cm (FL), males 18 cm (FL)). Life span is around 14 years (Taylor et al. 2014).
Means of Introduction: Probable aquarium release. This species is one of four tangs that together make up 90% of Hawaii's ornamental fish-export market (Kusumaatmadja et al. 2004).
The species is used a food fish in its native range (Randall 2001), even though it is rarely poisonous (Froese and Pauly 2005).
Status: Reported in Florida and Georgia.
Impact of Introduction: The impacts of this species are currently unknown, as no studies have been done to determine how it has affected ecosystems in the invaded range. The absence of data does not equate to lack of effects. It does, however, mean that research is required to evaluate effects before conclusions can be made.
References: (click for full references)
Allen, G., R. Steene, P. Humann and N. Deloach. 2003. Reef Fish Identification. Tropical Pacific. New World Publications, Inc., Jacksonville, Florida and Odyssey Publications, El Cajon, California.
Eschmeyer, W. N., C. J. Ferraris, Jr., M. D. Hoang and D. J. Long. 1998. A Catalogue of the Species of Fishes. Preliminary Version 2, November 1996. California Academy of Sciences. Available online at: https://www.calacademy.org/scientists/projects/eschmeyers-catalog-of-fishes
Froese, R. and D. Pauly. Editors. 2005. FishBase. World Wide Web electronic publication. www.fishbase.org, version (09/2004).
Kusumaatmadja, R., J. Parks, S. Atkinson and J. Dierking. 2004. Toward MAC certification of Hawaiian Islands collectors: a project update. Live Reef Information Bulletin 12: 26-28.
Myers, R. F. 1999. Micronesian Reef Fishes. A Field Guide for Divers and Aquarists. Coral Graphics, Davie Florida.
Nelson, S.G. and R.N. Tsutsui. 1981. Browsing by herbivorous reef-fishes on the agarophyte Gracilaria edulis (Rhodophyta) at Guam, Mariana Islands. Fourth International Coral Reef Symposium, Manila (Philippines), 18-22 May, 1981.
Randall, J.E. 2001. Acanthuridae. Surgeonfishes (tangs, unicornfishes). pp 3653-3683 In: Carpenter, K. E. and V. Niem (Eds.) FAO species identification guide for fishery purposes. The living marine resources of the Western Central Pacific. Vo. 6. Bony fishes part 4 (Labridae to Latimeriidae), estuarine crocodiles. FAO, Rome.
Reef. 2008. Reef Environmental Education Foundation. Exotic species sighting program and volunteer database. World wide web electronic publication. www.reef.org, date of download March 10, 2008).
Taylor, B.M., K.L. Rhodes, A. Marshell and J.L. McIlwain. 2014. Age-based demographic and reproductive assessment of orangespine Naso lituratus and bluespine Naso unicornis unicornfishes. Journal of Fish Biology 85:901-916.
Revision Date: 2/17/2020
Peer Review Date: 6/15/2009
Schofield, P.J., 2021, Naso lituratus (Forster in Bloch and Schneider, 1801): U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, https://nas.er.usgs.gov/queries/FactSheet.aspx?SpeciesID=2553, Revision Date: 2/17/2020, Peer Review Date: 6/15/2009, Access Date: 9/23/2021
This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.