Stone loaches from the headwaters of the Bulgan River (Mongolian Altai) (Teleostei: Cypriniformes: Nemacheilidae: Barbatula)

摘要

Twosympatric species of loaches, Barbatula cf. altayensis Zhu, 1992and B. karabanowi Prokofiev, 2018, occur in the upper reaches of theriver Bulgan in Mongolia. They represent the only fish taxa found in thestudied part of the river. Significant morphological differences between thesespecies support their apparent belonging to the different phyletic lineages. Barbatulacf. altayensis is characterized by the following combination ofcharacters: nostrils closely set; lips furrowed, upper lip with medialindentation weak to absent, lower lip with medial lobes barely separated,furrowed, lateral lobes absent; scale cover well developed; broad head withmuscular cheeks; 44–45 vertebrae; 89–105 lateral-line pores; pigmentationpattern consisting of transverse bars or isolated well spaced blotches. A setof peculiar features (mouth structure and position of nares, characters ofsexual dimorphism, strong ossification of the otic portion of the cephaliclaterosensory system) supposes an isolated position of B. altayensiswithin the genus. The second species, B. karabanowi,belongs tothe “blunt-snouted” complex of species related to B. toni sensu stricto.Within the other members of this complex it is most similar to B.dsapchynensis from the basin of Zavhan River (Lake Valley, Mongolia) butdiffers from this and other species of Barbatula by the followingcombination of characters: nostrils widely spaced; snout relatively broad,ratio between maximum head width and width of snout at anterior nares equal to1.44–1.57; lips smooth, upper lip with short indentation; lower lip with shortbut well developed lateral lobes and oval mental lobes lacking conicalprotrusions; scale cover reduced; 42–44 vertebrae (usually 43); 75–88lateral-line pores; paired fins with rounded tips; pigmentation pattern usuallywith densely distributed and partially fused irregular spots and streaks. Themorphological proximity between B. karabanowi and B. dsapchynensis mayindicate a possibility of links between the basins of Bulgan and Zavhan in thepast