''Acanthurus nigroris'', the bluelined surgeonfish, is a species of marine ray-finned fish belonging to the family

Acanthuridae Acanthuridae are the family of surgeonfishes, tangs, and unicornfishes. The family includes about 86 extant species of marine fish living in tropical seas, usually around coral reefs. Many of the species are brightly colored and popular in aq ...

, which includes the surgeonfishes, unicornfishes and tangs. This species and '' A. nigros'' have been regarded as

synonymous A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are all ...

with the combined taxon having a wide

Indo-Pacific The Indo-Pacific is a vast biogeographic region of Earth. In a narrow sense, sometimes known as the Indo-West Pacific or Indo-Pacific Asia, it comprises the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the ...

distribution, if treated as a separate valid species it is confined to the United States Pacific islands.

Taxonomy

''Acanthurus nigroris'' was first formally described in 1835 by the French zoologist

Achille Valenciennes Achille Valenciennes (9 August 1794 – 13 April 1865) was a French zoologist. Valenciennes was born in Paris, and studied under Georges Cuvier. His study of parasitic worms in humans made an important contribution to the study of parasitology. ...

with its type locality given as "Hawaiian island". In 1861 the German-born British zoologist Albert Günther described a new species ''Acanthurus nigros'' from the New Hebrides and in 1956

John E. Randall John Ernest "Jack" Randall (May 22, 1924 – April 26, 2020) was an American ichthyologist and a leading authority on coral reef fishes. Randall described over 800 species and authored 11 books and over 900 scientific papers and popular articles. ...

reviewed the genus '' Acanthurus'' and placed Günther's ''A. nigros'' in synonymy with ''A. nigroris'' but in 2011 workers, including Randall, have argued that genetic differences support the validity of ''A. nigros'' as a separate species from ''A. nigroris''. The genus ''Acanthurus'' is one of two genera in the tribe Acanthurini which is one of three tribes in the

subfamily In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end subfamily botanical names with "-oideae", and zoologi ...

Acanthurinae ''Acanthurinae'' is a subfamily of fish belonging to the family Acanthuridae, including 55 species in four genera. Description Among the species of the genera ''Acanthurus'' and ''Zebrasoma'' there are small anatomical differences: the fir ...

which is one of two subfamilies in the family Acanthuridae.

Etymology

''Acanthurus nigroris'' has the subspecific name, ''nigroris'' combining ''niger'', meaning "black", with ''oris'', meaning "mouth" a reference to the black lips Valenciennes described for this fish, these are not apparent in living specimens so may be a result of preservation in alcohol.

Description

''Acanthurus nigroris'' has its dorsal fin supported by 9 spines and between 23 and 26 soft rays while its

anal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...

is supported by 3 spines and 22-24 soft rays. It also has a anterior gill raker count of between 26 and 31. The overall colour of the body is pale to dark brown, with slightly irregular, horizontal, dotted blue lines thinner than the brown spaces between them. There are blue lines on the head below the eye and on the gill cover which run parallel to the snout. There is a black spot with a diameter less than half that of the eye at the posterior of both the dorsal and anal fins. There is frequently a thick whitish bar on the caudal peduncle. The dorsal and anal fins have horizontal reddish brown bands and a slender blue margin. The caudal fin has a thin white rear margin. The maximum

standard length Fish measurement is the measuring of individual fish and various parts of their anatomies. These data are used in many areas of ichthyology, including taxonomy and fisheries biology. Overall length * Standard length (SL) is the length of a fish m ...

is .

Distribution and habitat

''Acanthurus nigroris'' ''sensu stricto'' is found in the central Pacific Ocean where it is jnown only from the

Hawaiian Islands The Hawaiian Islands ( haw, Nā Mokupuni o Hawai‘i) are an archipelago of eight major islands, several atolls, and numerous smaller islets in the North Pacific Ocean, extending some from the island of Hawaii in the south to northernmost Kur ...

and

Johnston Atoll Johnston Atoll is an Unincorporated territories of the United States, unincorporated territory of the United States, currently administered by the United States Fish and Wildlife Service (USFWS). Johnston Atoll is a National Wildlife Refuge and ...

. This species is a generalist, as far as habitat is concerned, being found in schools which vary from a few individuals to hundreds inlagoons, on seaward reefs and in areas of mixed sand, rock and coral rubble. Here they graze on filamentous algae and feed on plankton.

References

{{Taxonbar, from=Q2496538 nigroris Fish of Hawaii Fish described in 1835 Taxa named by Achille Valenciennes