How to Identify Orangespine Unicornfish

To identify Orangespine Unicornfish (Naso lituratus), look at these key features.

Physical Characteristics

Body shape

compressed

Coloration

The body is typically grey to olive-brown, often with a yellowish wash. The dorsal fin is yellow with a thin blue margin, and the anal fin is brown with a blue margin. The caudal fin is dark, often with a pale posterior margin, and in males, it develops elongated filaments. A prominent yellow or orange band runs from the eye to the snout. The most distinctive feature is the two bright orange, blade-like spines (scalpel-like keels) on each side of the caudal peduncle, outlined in black.

Scale type

ctenoid

Mouth position

terminal

Distinctive features

Two prominent, bright orange, blade-like spines on each side of the caudal peduncle, outlined in black., Yellow dorsal fin with a blue margin., Yellow or orange band extending from the eye to the snout., Absence of a prominent frontal horn in most individuals, though a slight bump may develop in large adults., Males develop elongated filaments on the caudal fin.

Dorsal fin

VI spines, 26-30 soft rays; yellow with a blue margin.

Tail fin

Truncate to slightly emarginate, with elongated filaments in adult males; dark with a pale posterior margin.

Pectoral fin

17-18 rays; translucent to yellowish.

Distinctive fins

Anal fin with II spines and 27-30 soft rays; brown with a blue margin. Pelvic fins I spine, 3 rays.

Identification Tips

1. 1

   Caudal Peduncle Spines

   Look for the two distinct, bright orange, blade-like spines on each side of the tail base, outlined in black. This is the most definitive identifying feature.

2. 2

   Head Markings

   Observe the yellow or orange band that extends from the eye to the snout, contrasting with the darker body coloration.

3. 3

   Dorsal Fin Color

   Note the bright yellow dorsal fin with a thin blue margin.

4. 4

   Absence of Horn

   Unlike many other Naso species, N. lituratus typically lacks a prominent frontal horn, especially when young. Large adults may have a slight bump.

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