Naso caesius
A bluish-grey unicornfish found in Indo-Pacific reefs.
Naso caesius, commonly known as the grey unicornfish or silverblotched unicornfish, is a marine ray-finned fish in the family Acanthuridae, which also includes surgeonfishes and tangs. It is found in the Indo-Pacific region.
The species was first scientifically described in 1992 by American ichthyologist John Ernest Randall and marine biologist Lori Jane Bell Colin, based on a specimen from the northern side of the East Channel of Eniwetak Atoll in the Marshall Islands. It belongs to the nominate subgenus of the genus Naso, which is the sole genus in the subfamily Nasinae within Acanthuridae.
Its specific name, *caesius*, is Latin for "bluish grey," referring to the fish's overall coloration.
The dorsal fin has 6 or 7 spines and 27 to 30 soft rays, while the anal fin has 2 spines and 28 to 31 soft rays. The pectoral fin has 16 to 18 rays, with the upper two being unbranched. The caudal peduncle features oval keels with projecting spines that are not sharp. The body is bluish-grey or greyish-brown, and it can display irregular blotches or bars along the sides, which may be lighter or darker than the base color. The maximum recorded standard length is 45.6 cm (18.0 in).
This species is primarily found in the western Central Pacific, including Palau, the Mariana Islands, the northern Marshall Islands, the Hawaiian Islands, the Great Barrier Reef, Osprey Reef, the Chesterfield Islands, New Caledonia, Fiji, Tuvalu, the Society Islands, and the Pitcairn Islands. In Australian waters beyond the Great Barrier Reef, it occurs at Lord Howe Island, reefs in the Coral Sea as far south as the Kurnell Peninsula in New South Wales, and off Western Australia, as well as at Ashmore Reef, Christmas Island, and the Cocos (Keeling) Islands. The grey unicornfish is a benthopelagic species that lives over rock and coral substrates, either alone or in schools, in clear waters of lagoon reefs, reef channels, or seaward reefs at depths of 15 to 50 m (49 to 164 ft), where it feeds on zooplankton.
Quick Facts
- Parent
- Naso (Naso)
- Taxon
- Naso caesius
Facts from the source article.
Lore & Background
Naso caesius was first formally described in 1992 by American ichthyologist John Ernest Randall and marine biologist Lori Jane Bell Colin, with the type locality given as the northern side of the East Channel of Eniwetak Atoll in the Marshall Islands. This species is classified within the nominate subgenus of the genus Naso, which is the only genus in the subfamily Nasinae within the family Acanthuridae. Its specific name caesius is Latin for 'bluish grey', referring to its overall colour.
The grey unicornfish has 6 or 7 spines and between 27 and 30 soft rays supporting the dorsal fin, while the anal fin is supported by 2 spines and between 28 and 31 soft rays. The pectoral fin contains between 16 and 18 fin rays, with the upper two being simple and unbranched. The keels on the caudal peduncle are oval shaped with spines that project outward but are not acute. The overall colour is bluish-grey or greyish-brown, and they can create a series of irregular blotches or bars along the flanks, which may be lighter or darker than the background colour. This fish has a maximum published standard length of 45.6 cm.
Naso caesius is found mainly in the western Central Pacific, including Palau, Mariana Islands, the northern Marshall Islands, Hawaiian Islands, Great Barrier Reef, Osprey Reef, Chesterfield Islands, New Caledonia, Fiji, Tuvalu, Society Islands, and Pitcairn Islands. In Australian waters away from the Great Barrier Reef, it is known from Lord Howe Island and reefs in the Coral Sea as far south as the Kurnell Peninsula in New South Wales, as well as on reefs off Western Australia and at Ashmore Reef and the Indian Ocean islands of Christmas Island and the Cocos (Keeling) Islands. It is a benthopelagic species found over rock and coral substrates, occurring solitarily or in schools in clear waters in lagoon reefs, reef channels, or seaward reefs at depths between 15 and 50 m, where they feed on zooplankton.
Reader's Guide
Naso caesius is notable as a relatively recently described species of unicornfish, first formally identified in 1992. Its description by John Ernest Randall and Lori Jane Bell Colin added to the known diversity of the genus Naso, which is the sole genus in the subfamily Nasinae within the family Acanthuridae. The species' specific name, caesius, meaning 'bluish grey' in Latin, directly describes its overall coloration, which can also include irregular blotches or bars. The grey unicornfish is distinguished by its oval-shaped caudal peduncle keels with non-acute spines, and its dorsal and anal fin ray counts. Its distribution spans a wide area of the Indo-Pacific, from the western Central Pacific to the Indian Ocean, including locations such as the Hawaiian Islands, Great Barrier Reef, and Christmas Island. Ecologically, it is a benthopelagic species that inhabits clear waters over rock and coral substrates at depths of 15 to 50 m, where it feeds on zooplankton and may occur solitarily or in schools. This species contributes to the understanding of reef fish biodiversity and the biogeography of the Indo-Pacific region.
Frequently Asked Questions
What is Naso caesius?
Naso caesius is a bluish-grey reef fish popularly called the grey unicornfish or silverblotched unicornfish. It is a member of the family Acanthuridae, the same family that houses both tangs and surgeonfishes, and it sits squarely within the genus Naso.
Who first described Naso caesius and when?
American ichthyologist John Ernest Randall and marine biologist Lori Jane Bell Colin formally named the species in 1992. Their description was based on a single specimen taken from the northern side of the East Channel at Eniwetak Atoll in the Marshall Islands.
How big does Naso caesius get and what does its dorsal fin look like?
The grey unicornfish tops out at a standard length of roughly 45.6 cm (about 18 inches). Its dorsal fin carries six or seven spines followed by 27 to 30 soft rays.
Where in the wild can you find Naso caesius?
This species is a resident of coral-reef habitats throughout the Indo-Pacific region. Its type locality is the Marshall Islands, specifically the northern side of the East Channel of Eniwetak Atoll.
How does Naso caesius fit into the broader unicornfish taxonomy?
It belongs to the subfamily Nasinae, in which Naso is the sole recognized genus. Within that genus, Naso caesius is placed in the nominate subgenus, setting it apart from other unicornfish lineages.
More in Tangs and Surgeonfish 1-24
Spotted an error? Know more?
Reader corrections go straight into our review queue. Suggest an edit · How this site is sourced