Populations from the upper Pearl River (Nanpan Jiang basin) differ in several morphological characters from those inhabiting Guangdong, Guangxi, and Guizhou Provinces, and Hainan Island. Those from Vietnam also seem to be different (Gan et al., 2009), the implication being that there may be several species currently included under the name M. lineata.

Although it is included in the genus Metzia this grouping remains somewhat unresolved in terms of taxonomy and it may contain more than a single genetic lineage. For example, members share a number of characters with the genera Ischikauia Jordan and Snyder 1900, Hemiculterella Warpachowski 1887, and several species of Anabarilius Cockerell 1923, including a bipartite gas bladder, a non-spinous dorsal-fin ray, and a sharp ventral keel between the pelvic-fin insertion and anus.

This species can be distinguished from congeners inhabiting the Red River basin in Yunnan province, China, by the following combination of characters: no barbels; 46-52 lateral line scales; 16 circumpeduncular scales; pharyngeal teeth in 3 rows, 2.4.5-5.4.2; snout rounded, no secondary rostrum, no longitudinal…

This species is widely-distributed in the Mekong river system in Thailand, Laos, and Vietnam, Salween and Ayeyarwaddy rivers in southern China, Myanmar, and Thailand, plus various smaller basins in Vietnam and China. It has also been recorded from the islands of Hainan and Hong Kong.

Type locality is given as ‘China: sent from Hong Kong’.

A. iridescens and its closest relative A. longipinnis can be distinguished from all other barred species of Acrossocheilus by the following characters: wider (vs. narrower) black vertical bars on the flank in adults, each five to eight (vs. no more than four) scales in width; a horse-shoe shaped (vs. arched) mouth gape; rostral barbel located posteriorly (vs. anteriorly) to a horizontal line through the anteriormost margin of the lower jaw; two postlabial grooves extending anteromedially beyond (vs. away from) a horizontal line through the roots of the rostral barbels.

A. macropterus appears in the ornamental trade on an irregular basis and should only be considered by more experienced aquarists with sufficiently large facilities.

Given its wide geographical distribution there is a possibility that it represents a group of closely-related species, with genetic studies indicating the existence of several distinct clades.

Known from the from the Red River in northern Vietnam and Yunnan province, southern China, plus the Thái Bình, Sông Kỳ Cùng, Mã and Lam rivers in Vietnam and possibly the Nam Xam and Nam Ma drainages in Laos.

Type locality is ‘Market in Hanoi, Vietnam’.

No bubble nest is built and several thousand eggs simply float at the surface with both male and female remaining to defend the eggs and fry.

The eggs hatch after 24-36 hours depending on temperature and the fry are free swimming in a further 24 hours. At this point they resemble 6-7 mm long black tadpoles.

It is important to constantly feed…

This species appears to exist in a number of different forms which exhibit differences in colour pattern, morphology, or both, and it’s currently unclear whether all of them are truly conspecific or not although those in the aquarium trade all appear similar to one another.

We’ve been unable to obtain a copy of the original description so it’s not currently possible to provide a detailed diagnosis either, with most recent studi…

Generally considered to have an enormous natural range extending from Iran to Taiwan and Bali, with records existing from Iran, Iraq, Afghanistan, Pakistan, Nepal, India, Sri Lanka, Bangladesh, Bhutan, China, Myanmar, Thailand, Laos, Cambodia, Vietnam, Malaysia, Indonesia, and Singapore.

However there exists significant evidence to suggest that C. gachua as currently understood represents a complex of similar-looking species, and a taxonomic review of the group is clearly required.