Fish
Blacktongue Unicornfish
Naso hexacanthus
A smooth-headed, hornless unicornfish that shoals in midwater over reefs, told by the black tongue it develops as it grows.
- Typical size
- Attains about 75 cm
- Habitat
- Midwater near reefs
The blacktongue unicorn lacks the projecting horn of some relatives, having instead a smoothly convex head profile, and is brown to bluish-grey above shading to yellowish below. Its name comes from the tongue, which turns black in fish of about 25 cm and larger; courting males can flush a large pale-blue patch over the head and forebody.
It attains around 75 to 80 cm and ranges through the Indo-Pacific south to Bazaruto in Mozambique. Often seen in shoals hanging in midwater near reefs, it feeds largely on zooplankton and settles onto the reef to sleep at night.