Stone Loaches, Nemacheilidae, are freshwater Cypriniform Fish found throughout Eurasia, with one genus occurring in Ethiopia. They favour fast moving stretches of small streams, but are occasionally found in larger rivers, and even caves. The group currently contains about valid 790 species in 53 genera, with new species being described on a regular basis, particularly from Southeast Asia. The genus Nemacheilus currently includes 36 species from the Chao Phraya, Mae Khlong,
and Mekong river drainages, the Malay Peninsula, and the islands of Sumatra, Java and
Borneo. Members of this genus tend to be found in streams and rivers with slow to moderate flows and sand, gravel, or pebble bottoms.
In a paper published in the Raffles Bulletin of Zoology on 20 February 2023, Maurice Kottelat of the Lee KongChian Natural History Museum at the National University of Singapore, describes a new species of Nemacheilus from central Laos.
The new species is named Nemacheilus pullus, where 'pullus' is intended to mean dark yellow to blackish. The species is described from populations living in the Nam Ngiep and Nam
Xan watersheds of the the Mekong drainage in central Laos, which were previously assigned to the species Nemacheilus platiceps.
Nemacheilus pullus, Laos: Mekong drainage: Nam Ngiep watershed; (a) CMK 27518, paratype, male, 37.7 mm; (b) MHNG
2787.091, holotype, male, 41.5 mm; (c) CMK 27518, paratype, female, 64.1 mm. Note that in b the specimen is slightly tilted
laterally and the eye appears more distant from the dorsal profile than in reality. Kottelat (2023).
Nemacheilus pullus shares with Nemacheilus platiceps an incomplete lateral line, whereas in almost all other members of the genus the lateral line is complete. However Nemacheilus pullus lacks the clear flank bars of Nemacheilus platiceps, instead being a plain yellowish grey in colour (juveniles, and some adult females, do have faint bars, but these are much less clear than in Nemacheilus platiceps).
Nemacheilus platiceps; (a) CMK 21392, 27.8 mm; Laos: Mekong drainage: Xe Kong watershed; (b)–(d) CMK 7927, Vietnam:
Dong Nai drainage, 36.2 mm, (b) reversed) 40.8 mm, 54.4 mm, (d) reversed; and (e) NRM 15095, holotype, 40.1 mm; Vietnam
Dong Nai drainage (reversed). Kottelat (2023).
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