Achilles Tang

The Achilles Tang (Acanthurus achilles) is a surgeonfish in the family Acanthuridae, named for the vivid orange marking near its tail reminiscent of the mythological Achilles' heel. It is native to the tropical Pacific, most abundant around Hawaii, French Polynesia, and other central Pacific island groups. The species is not considered threatened and is a popular subject for underwater photography due to its bold coloration. Like other surgeonfish, it possesses a sharp, blade-like spine on either side of the tail base used defensively. It is closely related to other black-bodied surgeonfish but is distinguished by its unique orange tail patch.

Distinguishing features include:

• Deep, oval, laterally compressed body
• Overall glossy black coloration
• Large orange-red teardrop-shaped patch surrounding the tail base
• Matching orange band along the trailing edge of the caudal fin
• Sharp white scalpel spine on the caudal peduncle
• Adult size typically 18-24 cm The combination of solid black body and orange tail marking is unique among Pacific surgeonfish, making misidentification unlikely, though it can superficially resemble the Whitecheek Surgeonfish at a distance.

Achilles Tangs favor shallow, high-energy reef environments with strong surge and wave action, typically in depths from the surface down to about 6 m, occasionally to 15 m. They are most common along exposed outer reef slopes and reef crests in the central and western Pacific, with particular abundance around the Hawaiian Islands and French Polynesia. They prefer clear, well-oxygenated tropical water where turbulent surf promotes algal growth on rock and coral surfaces. Their tolerance for rough surf conditions sets them apart from many reef fish that avoid such turbulent zones.

Achilles Tangs are diurnal algae grazers, using specialized teeth to scrape filamentous algae from rocky and coral surfaces in the turbulent shallows they favor. They can be territorial, particularly males defending feeding areas, but are also seen foraging in loose aggregations or mixed-species groups with other surgeonfish, which may reduce individual aggression from resident fish. When threatened, they can rapidly flick their tail to bring the sharp caudal spine to bear as a defensive weapon. Spawning follows a broadcast pattern typical of surgeonfish, with pairs or groups releasing eggs and sperm into open water during dusk periods, after which larvae disperse in the plankton before settling on reef habitat.