Achilles Tang

Max length : 24.0 cm TL male/unsexed

Family	Acanthuridae
Description	Surgeonfishes, tangs, unicornfishes
Environment	Marine
Etymology	Greek, akantha = thorn + oura = tail
Genus	6
No. of Species	82
Order	Perciformes
Class	Actinopterygii
Reproductive Guild	Nonguarders
Distribution	Circumtropical, especially around coral reefs; five species in the Atlantic, the remaining in the Pacific and Indian oceans. All have a deep compressed body with the eye high on the head and a long preorbital bone. Single unnotched dorsal fin with 4-9 spines and 19-31 rays; anal fin with 2 (only Naso) or 3 spines and 19-36 rays; pelvic fins with 1 spine and 3 (Naso and Paracanthurus) or 5 rays. Very small ctenoid scales. A small terminal mouth with a single row of close-set teeth. Most surgeon fishes graze on benthic algae and have a long intestine; some feed mainly on zooplankton or detritus. Surgeon fishes are able to slash other fishes with their sharp caudal spines by a rapid side sweep of the tail. Pelagic spawners. Many species have bright colors and are popular aquarium fishes.

Occurs in clear seaward reefs, usually in groups. Benthopelagic. Feeds on filamentous and small fleshy algae. Monogamous. Spine in caudal peduncle may be venomous. Size of metamorphosis from postlarva stage to juvenile is 6 cm. This species sometimes hybridizes with A. nigricans

Dorsal spines (total): 9; Dorsal soft rays (total): 29-33; Anal spines: 3; Anal soft rays: 26 - 29. Dark brown, nearly black in color. Erectile spine (sharp and forward-pointing) on each side of caudal peduncle which folds down into a groove. Mouth small, snout noticeably extended. Light blue ring around chin and presence of spot of same color on gill cover at angle of gill opening. Dorsal fin with soft part having longer base than spinous part. Juveniles lack the large orange spot on caudal area.

Summary of Distribution: Western Pacific: oceanic islands of Oceania to the Hawaiian and Pitcairn islands. Also known from Wake, Marcus, and Mariana islands. Eastern Central Pacific: southern tip of Baja California, Mexico and other offshore islands.
Note: Distribution range colors indicate degree of suitability of habitat which can be interpreted as probabilities of occurrence (fishbase.org)