Ctenochaetus

Lore & Background

The genus Ctenochaetus was first proposed in 1884 by American biologist Theodore Gill, with Acanthurus strigosus as its type species. That species had originally been described in 1828 by Edward Turner Bennett from the Sandwich Islands. The name Ctenochaetus is a compound of cteno, meaning “comb,” and chaetus, meaning “bristle,” almost certainly alluding to the bristle- or comb-like teeth of these fishes.

Ctenochaetus surgeonfishes are closely related to those in the genus Acanthurus and are very similar to them, but they differ in jaw structure, possessing numerous brush- or bristle-like flexible teeth. Their dorsal fin is supported by 8 spines and between 24 and 31 soft rays, while the anal fin has 3 spines and between 22 and 28 soft rays. These fish vary in length from a maximum published standard length of 15 cm in C. strigosus to a maximum published total length of 27 cm in C. marginatus.

There is taxonomic dispute regarding the genus: it has been proposed that Ctenochaetus and Acanthurus should be merged, as otherwise Acanthurus is paraphyletic. Ctenochaetus species all nest within Acanthurus, while A. nubilus and A. pyroferus are further nested within Ctenochaetus. The 5th edition of Fishes of the World, however, recognizes both genera as valid and classifies them as the two genera in the tribe Acanthurini.

Reader's Guide

Ctenochaetus holds a notable place in the taxonomy of surgeonfishes due to ongoing debate about its relationship with the genus Acanthurus. The proposal to merge the two genera stems from evidence that Ctenochaetus species nest within Acanthurus, while two Acanthurus species nest within Ctenochaetus, indicating paraphyly. Despite this, the 5th edition of Fishes of the World maintains both as valid genera within the tribe Acanthurini. The genus is distinguished by its unique dentition—numerous small, flexible, bristle-like teeth—which sets it apart from typical Acanthurus surgeonfishes.

These fishes are widely distributed across the Indo-Pacific, from the eastern coast of Africa and the Red Sea to the tropical Indian Ocean and Pacific Ocean as far east as Hawaii. Their maximum sizes range from about 15 cm to 27 cm depending on species. The nine recognized species contribute to the diversity of the family Acanthuridae, and the genus remains a subject of taxonomic interest.