AT A GLANCE
- Common Name: Orangespine Unicornfish
- Scientific Name: Naso lituratus
- Category: Fish
- Subcategory: Bony Fishes
- Range: Central and western Pacific Ocean, from Japan, Taiwan, and the Philippines east through Micronesia and Melanesia to Hawaii, the Tuamotu Archipelago, and the Great Barrier Reef
- Habitat Type: Lagoon patch reefs, seaward coral reef slopes, surge channels, and shallow reef flats exposed to open ocean swells from 1 to 90 meters depth
- IUCN Red List Status: Least Concern
- Lifespan: 20 to 30 years (exceptionally long-lived for a reef fish)
- Diet: Herbivorous/Algivorous (specialized grazing on coarse brown macroalgae, particularly Sargassum and Dictyota)
- Average Size/Weight: Total length 35 to 45 cm; weight 1 to 2.2 kg
- Key Defining Feature: Slate-grey unicornfish lacking a rostral horn, featuring bright orange ‘lipstick’ lips, a yellow eye streak, and two pairs of brilliant neon-orange knife-like spines on its tail
Overview
The Orangespine Unicornfish (Naso lituratus), affectionately known across Hawaii as ‘Kala’ or the ‘Lipstick Tang,’ is an iconic, exquisitely colored marine herbivore in the surgeonfish family Acanthuridae. Despite belonging to the unicornfish genus Naso, it is one of several species that completely lacks the prominent rostral forehead horn. Instead, it is celebrated for its dazzling cosmetic facial markings, featuring bright orange lips that look like freshly applied lipstick and two pairs of razor-sharp, bright orange defensive peduncle spines that stand out like warning beacons on its tail.
Biology and Physical Characteristics
Naso lituratus has an elongated, oval-shaped, highly compressed body covered in tiny, non-overlapping scales that give its skin a velvety texture. Its body coloration is an elegant, dusky slate-grey to olive-brown with a pale yellowish abdomen. Its facial coloration is spectacular: its pouty mouth is outlined in intense, glowing orange ‘lipstick,’ bordered by a black mask that extends up to its eyes, which are crowned by a vivid lemon-yellow bar across the forehead. Its caudal peduncle features two pairs of large, fixed, forward-curving, razor-sharp bony blades set within bright, fluorescent orange oval patches. In mature males, the outer lobes of the lyre-shaped caudal fin develop long, elegant filament streamers.
Behavior and Ecology
Orangespine Unicornfish are diurnal, nomadic grazers of the coral reef. Moving individually or in small loose schools, they roam across seaward reef flats and surge channels, using their small, sharp teeth to browse on tough, fibrous leafy brown macroalgae such as Sargassum and Dictyota that other herbivorous fishes avoid, preventing macroalgae from overgrowing and suffocating live coral. When threatened by reef sharks, the unicornfish turns sideways and flexes its tail, displaying its sharp orange tail scalpels to deter attackers with painful defensive lacerations.
Conservation and Human Impact
The Orangespine Unicornfish is evaluated as Least Concern by the IUCN Red List. It is abundant across its vast Pacific range and maintains stable wild populations. It is traditionally harvested by Hawaiian and Pacific Island spearfishers as a prized food fish and collected in moderate numbers for public and private marine aquariums.
Interesting Factoid
The Orangespine Unicornfish has natural bright orange ‘lipstick’ around its mouth and two pairs of bright orange daggers on its tail that stay razor-sharp to slice predatory sharks that get too close.