Mystacoleucus atridorsalis FOWLER, 1937

Etymology

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.

Classification

Order: Cypriniformes Family: Cyprinidae

Distribution

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’.

Habitat

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.

Maximum Standard Length

At least 80 mm.

Diet

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

NotesTop ↑

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.

References

1. Fowler, H. W., 1937 - Proceedings of the Academy of Natural Sciences of Philadelphia v. 89: 125-264
   Zoological results of the third De Schauensee Siamese Expedition. Part VIII - Fishes obtained in 1936.
2. Kottelat, M., 2013 - Raffles Bulletin of Zoology Supplement 27: 1-663
   The fishes of the inland waters of southeast Asia: a catalogue and core bibiography of the fishes known to occur in freshwaters, mangroves and estuaries.
3. Kottelat, M., 2001 - WHT Publications, Colombo: 1-198
   Fishes of Laos.
4. Kottelat, M., 2000 - Journal of South Asian Natural History 5(1): 37-82
   Diagnoses of a new genus and 64 new species of fishes from Laos (Teleostei: Cyprinidae, Balitoridae, Bagridae, Syngnathidae, Chaudhuriidae and Tetraodontidae).
5. Kottelat, M., 1998 - Ichthyological Exploration of Freshwaters 9(1): 1-128
   Fishes of the Nam Theun and Xe Bangfai basins, Laos, with diagnoses of twenty-two new species (Teleostei: Cyprinidae, Balitoridae, Cobitidae, Coiidae and Odontobutidae).
6. Rainboth, W. J., 1996 - FAO, Rome: 1-265
   FAO species identification field guide for fishery purposes. Fishes of the Cambodian Mekong.