Black-barred wrasse
A southwestern Pacific wrasse often mistaken for Jansen's wrasse.
The black-barred wrasse (Thalassoma nigrofasciatum) is a ray-finned fish belonging to the wrasse family Labridae, found in the southwestern Pacific Ocean. Adults have a blackish upper body, with the lower half of the head, chest, and belly colored white. A short white to yellow vertical stripe sits above the base of the pectoral fin, and two broader white to yellow stripes run along the flanks; the tail is yellow. In females, the pale areas are mostly white, while in males these areas are more yellow. Males also have a pale pink chin, long thin filaments on the lobes of the tail fin, and pink patches on the lower head and chest. Males can reach a standard length of 20 cm. This species is often mistaken for the similar Jansen's wrasse (Thalassoma janseni).
Its range extends from eastern Papua New Guinea and the Solomon Islands south to the Great Barrier Reef, Lord Howe Island, Norfolk Island, the Kermadec Islands, New Caledonia, and Tonga, with a record also from Niue. The black-barred wrasse inhabits tidal pools and both inner and outer reefs at depths from 0 to 15 meters, living either alone or in small groups.
The species was first described in 2003. It is closely related to Jansen's wrasse, and the two are easily confused. While they share many molecular characteristics, they differ by a single nucleotide in the cytochrome b sequence. Although morphologically nearly identical, they are most likely separate, valid species, and past confusion may have affected previously reported distributions.
Quick Facts
- Scientific name
- Thalassoma nigrofasciatum
- Family
- Labridae
- Maximum standard length
- 20 cm (males)
- Depth range
- 0 to 15 m
Facts from the source article.
Lore & Background
The black-barred wrasse was described in 2003. Adults are blackish above with the ventral half of the head, chest, and belly white. A short white to yellow vertical stripe starts above the pectoral-fin base, and two broad white to yellow stripes run along the flanks, with a yellow tail. In females, the pale areas are largely white, while in males they are more yellow; males also have a pale pink chin, long thin filaments on the lobes of the caudal fin, and pink patches on the ventral parts of the head and chest. Males reach a standard length of 20 cm.
This species occurs in tidal pools and reefs, both inner and outer, from 0 to 15 m depth, and can be found solitarily or in small groups. It is closely related to Jansen's wrasse (Thalassoma janseni), and the two species are morphologically almost identical. They share many molecular characteristics but differ in a single nucleotide of the cytochrome b sequence. Despite this, they are each most probably separate and valid species, and there may have been confusion over identification in previously stated distributions.
Reader's Guide
The black-barred wrasse holds significance as a recently described species that highlights the challenges of distinguishing closely related reef fishes. Its near-identical appearance to Jansen's wrasse, coupled with a single nucleotide difference in the cytochrome b gene, underscores the subtle genetic boundaries that can separate species in the genus Thalassoma. This has implications for understanding biodiversity in the southwestern Pacific, as past distribution records may have conflated the two species. The black-barred wrasse's presence across a range of habitats—from tidal pools to inner and outer reefs—and its solitary or small-group behavior contribute to its ecological role in these environments. Its description in 2003 adds to the growing knowledge of wrasse diversity in the region, and its frequent confusion with Jansen's wrasse serves as a cautionary example for taxonomic work relying solely on morphology.
Frequently Asked Questions
What is the Black-barred wrasse?
It is a ray-finned fish in the wrasse family Labridae, scientifically known as Thalassoma nigrofasciatum, native to the southwestern Pacific Ocean. It is a small, colorful reef species that hobbyists sometimes confuse with Jansen's wrasse.
What does a Black-barred wrasse look like?
Adults display a dark upper body contrasted with a pale lower head, chest, and belly, along with two broad pale stripes running down the flanks and a yellow tail. A short pale stripe also sits just above the pectoral-fin base.
Where does the Black-barred wrasse live?
Its range stretches from eastern Papua New Guinea and the Solomon Islands southward to the Great Barrier Reef, Lord Howe Island, Norfolk Island, the Kermadec Islands, New Caledonia, Tonga, and Niue. It typically occupies shallow reef habitats from the surface down to about 15 m.
More in Wrasses and Gobies, Part 2 1-24
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