Naso Tang

The Naso Tang, or orangespine unicornfish, is a large surgeonfish (family Acanthuridae) in the genus Naso, widely distributed across Indo-Pacific coral reefs. Unlike true "unicornfish" species, it lacks a forehead horn but is still grouped with them due to close relation. It is a common, ecologically important herbivore/browser on outer reef slopes and is popular in the marine aquarium trade for its bold coloration. Populations are widespread and stable, and the species plays a significant role in controlling macroalgae growth on reefs.

• Deep, oval, laterally flattened body
• Gray to olive-brown coloring, darkening toward a black caudal peduncle
• Bright orange band along the lips ("lipstick" mark) and orange margin on the dorsal fin
• Yellow, blade-shaped marking near the base of the tail
• Sharp, movable orange scalpel spines on either side of the tail base, used defensively
• Lunate tail; adults reach 35-46 cm

Distinguished from other Naso species by lack of a nasal horn combined with the orange lip and yellow tail-base marking.

Naso Tangs inhabit clear outer reef slopes, channels, and lagoons throughout the Indo-Pacific, from East Africa to the central Pacific and north to southern Japan. They are typically found at depths of 1-90 m in warm tropical water, often near strong currents that carry drifting algae and plankton. Juveniles shelter in shallower reef areas with more cover, while adults range more widely over open reef terrain, often forming loose foraging groups over algae-covered rock and rubble.

This species grazes on leafy brown macroalgae, and as it matures, its diet broadens to include some zooplankton, making it an important control on algal overgrowth on reefs. Naso Tangs are often seen in schools of drab-colored individuals that turn brighter when displaying or interacting, and males can rapidly shift coloration during territorial or courtship encounters. They use their sharp caudal spines defensively against rivals or predators, erecting them when threatened. Spawning typically occurs in group aggregations near reef edges at dusk.