Mystacoleucus chilopterus

Mystacoleucus: from the Ancient Greek μύσταξ (mústaks), meaning 'upper lip, moustache', and the generic name Leuciscina, which is not currently in use.

chilopterus: from the Ancient Greek χείλος (cheílos), meaning 'lip', and πτερόν (pterón), meaning 'fin', in reference to the dark distal margins on the dorsal and caudal fins in this species.

Known from the middle Mekong basin in Laos and Thailand, including the Mun tributary drainage on the Khorat Plateau in northeastern Thailand, plus the Chao Phraya and Mae Klong watersheds in central and western Thailand, respectively. In the Mekong system it may also occur further upriver in Yunnan province, China, while the Khone Falls in Laos appear to represent its downstream limit.

Kottelat (2001) reports that it is also present in the Malay Peninsula, but records seem scarce.

Type locality is 'Thailand: Srisawat [Si Sawat, on Khwae Yai, a branch of Mae Khlong, 94 miles north-northwest of Ratchaburi; Smith, 1945: 26; 14°41'21"N 99°01'39"E]'.

A pelagic species displaying a preference for flowing, lowland river channels and swiftly-flowing forest streams with rock and gravel substrates.

This species can be distinguished from congeners by the following combination of characters: anal-fin with a concave distal margin; 22-24 + 2 lateral line scales; 14 circumpeduncular scale rows; 6-8 predorsal scales; dorsal-fin with black anterior and distal margins; caudal-fin with black margin; a few scales on anterior portion of the body with black, crescent-shaped markings.

All Mystacoleucus species possess a procumbent predorsal spine orientated towards the head, though it can be difficult to spot with the naked eye. This can become entangled in an aquarium net so care must be taken when handling the fish.

The trait is shared by members of Tor, Spinibarbus and Paraspinibarbus although there exists no strong evidence to suggest that these genera form a monophyletic lineage and it is likely that they developed the spine independantly of one another. Mystacoleucus spp. can be further identified by the presence of 6-10 branched anal-fin rays and 24-39 lateral line scales.