Mystacoleucus atridorsalis

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

atridorsalis: from the Latin ater, meaning 'black', and dorsum, meaning 'the back', in reference to the distinctive dark distal marking in the dorsal-fin.

Considered endemic to the lower Mekong River basin in Laos, Thailand, and Cambodia, including major tributaries such as the Xe Bang Fai in Laos, and the Mun and Songkhram watersheds in Thailand.

Records from central and western Thailand are misidentifications and do not represent M. atridorsalis.

Type locality is 'Mekong River at Kemarat, Thailand'.

A pelagic species displaying a preference for flowing, lowland river channels, but moves into flooded forests and other inundated zones during the wet season. It has also been collected in swiftly-flowing forest streams with gravel substrates.

Wild fish are omnivorous generalists, feeding on a range of aquatic invertebrates, organic detritus, and algae.

This species can be distinguished from congeners by the following combination of characters: body depth fits 2.5-2.7 times in SL; 28-31 +2-3 lateral line scales; 14-16 circumpeduncular scale rows; 5-5½ scale rows between the lateral line and dorsal-fin origin; a triangular distal blotch on the dorsal-fin; a few body scales with crescent-shaped black edges; a thin dark margin on the dorsal-fin, posterior to the distal blotch; a dark posterior margin on the caudal-fin; normally a single pair of rudimentary barbels present.

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.