Orangespine Unicornfish

The Orangespine Unicornfish, sometimes called the Lipstick Tang, is a strikingly marked member of the genus Naso within the family Acanthuridae. Unlike many other unicornfishes, adults lack a prominent forehead horn, but they are easily recognized by a bold black facial mask, yellow dorsal stripe, and vivid orange spines at the base of the tail. It is distributed across the Indo-Pacific, from the Andaman Sea and Christmas Island to Hawaii and the Pitcairn Islands, typically inhabiting shallow coral reefs. The species is a popular subject for underwater photography due to its bright coloration and is commonly kept in the marine aquarium trade. It is not currently considered threatened.

Distinguishing features of the Orangespine Unicornfish include:

• Oval body in grey to olive-brown
• Bold black mask running through the eye
• Bright yellow stripe along the top of the back near the dorsal fin
• Orange-yellow lips
• Two vivid orange, knife-like fixed spines on each side of the caudal peduncle

Adults reach about 46 cm and, unlike the Bluespine Unicornfish, do not develop a forehead horn. The bright orange tail-base spines combined with the black eye mask make this one of the most readily identifiable unicornfishes on Indo-Pacific reefs.

Orangespine Unicornfish inhabit shallow coral reefs, reef flats, and outer reef slopes across the tropical Indo-Pacific, from the eastern Indian Ocean to Hawaii and French Polynesia, generally at depths of 1-90 m though most common in shallower water. They favor areas with mixed coral and rocky substrate supporting brown macroalgae growth, their primary food source. Juveniles often settle in sheltered shallow reef flats before adults move to slightly more exposed reef edges. The species is commonly encountered by divers and snorkelers on shallow fringing and lagoon reefs throughout its broad Indo-Pacific range.

This unicornfish feeds mainly on brown macroalgae, browsing fronds from reef and rock surfaces during daylight hours. It is often seen alone, in pairs, or in small loose groups, though larger aggregations can form around abundant algal growth or for spawning. The bright orange caudal spines serve as an effective defensive weapon, used in slashing strikes against rivals or predators when the fish flexes its tail sideways. Territorial disputes with other unicornfish or surgeonfish can occur over algae-rich feeding areas. Spawning follows the broadcast pattern typical of the family, with eggs and sperm released into open water and larvae developing pelagically before settling onto reef habitat.