Mystacoleucus ectypus

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

ectypus: from the Latin ectypus, meaning 'in relief', in allusion to the presence of a small hump with the procurrent spine anterior to the dorsal-fin.

Known from the middle Mekong basin in Laos and Thailand, and may be endemic to the Khorat Plateau. Records exist from the Mun and Songkhram watersheds in northeastern Thailand, and a number of Mekong tributaries in laos, including the Nam Mang and Nam Kou drainages.

Type locality is 'Nam Mang downstream of Ban Thabok, between 18°22'25"N, 103°13'30"E, and about 1 kilometer upstream, Vientiane Province, Laos'.

A pelagic species displaying a preference for flowing lowland river channels and swiftly-flowing tributary streams and small-to-medium sized rivers with substrates of rock and gravel.

This species can be distinguished from congeners by the following combination of characters: body depth measures 34.5-38.7 % (fits 2.6-2.9 times) SL; 33-37 + 2-4 lateral line scales; 7½-8/1/5-6½ scales in transverse row anterior to pelvic-fin origin, 3½-4/1/3½ scales in transverse row on caudal peduncle; 16-17 circumpeduncular scales; 9-10½ branched anal-fin rays; presence of a triangular distal blotch at tip of dorsal fin; no black distal margins on dorsal or caudal fins; no black crescent-shaped markings on body scales; barbels absent or very rudimentary.

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.