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| Yunnanilus triangulus Liu, Lyu, Du & Chen, 2025 |
Abstract
A new species of the genus Yunnanilus, designated Yunnanilus triangulus sp. nov., is described from the Nanpan River in Yunnan Province, southwestern China. Nuptial males of this species are distinguished by the presence of tubercles on the caudal peduncle during the reproductive period, a feature not observed in other members of the genus. The new species is further characterized by the following unique combination of morphological characters: body scaled, smaller eyes than interorbital width, nine inner gill rakers on first gill arch, lateral head length 27.1%–30.9% SL, head width 14.3%–17.2% SL, eye diameter 19.6%–23.8% of lateral head length, and caudal peduncle depth 94.0%–130.6% of its length. Morphological and molecular evidence support the validity of this species, despite its geographic proximity to Y. polylepis. These findings underscore the ecological specialization that exists within the genus Yunnanilus and highlight the urgent need for species-specific conservation strategies, given their restricted distributions and dependence on specific habitats.
Key Words: Caudal peduncle with tubercles, freshwater fish, morphological characters, sexual dimorphism
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| Morphometric characters of Yunnanilus triangulus sp. nov. A–D. Lateral, dorsal, and ventral views, as well as a living photo of male, paratype KIZ2018002405; E–H. Lateral, dorsal, ventral, and living photo of female, holotype KIZ2018002410. Scale bar: 1 cm. |
Yunnanilus triangulus sp. nov.
Diagnosis. The new species can be distinguished from all other members of the genus by the presence of a unique triangular tubercle on the male caudal peduncle. It shares a body covered by scales, except on head and thorax, with Y. chuanheensis, Y. jiuchiensis, Y. longibulla, Y. macrogaster, Y. macrolepis, Y. parvus, Y. pleurotaenia, Y. polylepis, and Y. spanisbripes. However, the new species can be readily differentiated from these congeners by the following combination of characters: eye diameter shorter than interorbital width (vs. longer in Y. jiuchiensis and Y. longibulla), outer gill raker absent (vs. present in Y. macrolepis and Y. spanisbripes), processus dentiformis absent (vs. present in Y. macrogaster, Y. parvus, and Y. pleurotaenia), six branched pelvic-fin rays (vs. seven or eight in Y. chuanheensis), eight branched dorsal-fin rays (vs. nine in Y. polylepis), and specific metric characters.
Etymology. The specific name triangulus is derived from the unique presence of a tubercle on the caudal peduncle in nuptial males, a character not previously recorded in the genus Yunnanilus.
We suggest the Chinese vernacular name “三角云南鳅” and the English vernacular name “triangle Yunnan loach.” Gender: masculine.
Mei Liu, Jian-Bing Lyu, Li-Na Du, Xiao-Yong Chen. 2025. Description of A New loach Species, Yunnanilus triangulus sp. nov. (Cypriniformes, Nemacheilidae), from Yunnan, China. Zoosystematics and Evolution. 101(2): 465-471. DOI: doi.org/10.3897/zse.101.136965
