Yunnanilus mentibarbatus, Chen & Du & Liang, 2025

Yunnanilus mentibarbatus sp. nov.

Type materials.

Holotype. • KIZ 2024010565 View Materials , female, 68.3 mm standard length (SL), Jiuxiang Village , Yiliang County, Kunming City, Yunnan Province, P. R. China; a stream within the Nanpanjiang River basin; 24.8849°N, 103.1672°E; M. Q. Duan collected in December 2024 GoogleMaps .

Paratypes. • Five specimens. KIZ 2024010566 –570 View Materials , female, 40.3–54.2 mm SL; same as holotype GoogleMaps .

Other materials.

• DLN 20240615 –620, 35.5–48.9 mm SL, preserved in 99 % ethanol for molecular analysis, same as type specimens GoogleMaps .

Etymology.

The specific name mentibarbatus is derived from the Latin words mentum (chin) and barbatus (bearded or barbels), in reference to the unique short barbel on the mentum in female (Fig. 1 D View Figure 1 ). Gender: Masculine. We suggest the Chinese vernacular name “ 颏须云南鳅 ” and the English vernacular name “ mentum barbel Yunnan loach. ”

Diagnosis.

Comparative data between Yunnanilus mentibarbatus sp. nov. and all known species within the genus Yunnanilus are provided in Table 2 View Table 2 . The new species can be distinguished from congeneric species of Yunnanilus by the unique character, a pair of short barbels on the mentum in female. In addition, the new species can be further distinguished from other species of Yunnanilus by the following characters: whole body covered by scales; lateral line incomplete, with 16–21 pores; processus dentiformis present (Fig. 1 C View Figure 1 ); eye diameter shorter than interorbital width; 10–11 branched pectoral-fin rays; six branched pelvic-fin rays; six branched anal-fin rays; 16 branched caudal-fin rays; 11 inner gill rakers on first gill arch.

Description.

All morphometric and meristic data are given in Table 3 View Table 3 . Body covered by dense scale; deepest body depth 15.6–20.5 % of SL located anterior to dorsal fin origin, decreasing from dorsal-fin origin to caudal-fin base (Fig. 2 View Figure 2 ). Head length greater than its depth, head length 23.7–26.5 % of SL. Snout slightly blunt, shorter than postorbital length of head. Processus dentiformis present. Mouth inferior, middle of lower lip with notch, both lips have tangible wrinkles. Eyes normal, eye diameter 16.3–23.2 % of head length ( HL), smaller than interorbital width. Anterior and posterior nostrils separated by a short distance, posterior nostril closer to anterior margin of eye than to tip of snout, base of anterior nostril tube-shaped, without barbel-like tip, anterior nostril length 8.1–12.1 % of eye diameter.

Possessing a pair of short barbels on the mentum in female. Three pairs of barbels, two rostral pairs and one maxillary pair; inner rostral barbel length 25.1–33.6 % of HL; outer rostral barbel length 29.9–38.8 % of HL, reaching posterior nostril; maxillary barbel length 31.8–41.7 % of HL, reaching posterior margin of opercula.

Dorsal fin with four unbranched and eight branched rays; dorsal-fin origin anterior to pelvic-fin origin; pectoral fin with one unbranched and 10–11 branched rays, inserted immediately anterior to vertical through posterior point of operculum; pelvic fin with one unbranched and six branched rays, tips of pelvic fin not reaching anus; anal fin with three unbranched and six branched rays, length between tip of anal fin and anus origin 52.7–95.1 % of eye diameter; caudal fin emarginate, with 16 branched rays. Lateral line incomplete, with 16–21 pores, reaching tip of pectoral fin and anterior to dorsal fin origin; 11 inner gill rakers on first gill arch (in three specimens). Cephalic lateral system with 11–13 + 4 – 5 infraorbital canal pores, 7–8 supraorbital canal pores, 6 supratemporal canal pores, and 11 preoperculomandibular canal pores.

Stomach U-shaped (Fig. 1 A View Figure 1 ), intestine long and straight. Swim bladder divided into two chambers and connected by a slender tube, tube length about 1 / 2 of posterior chamber length; anterior chamber covered by dumbbell-shaped bony capsule, posterior chamber developed (Fig. 1 B View Figure 1 ).

Coloration.

In life, females have a light golden yellow head and trunk (Fig. 2 D View Figure 2 ). Ventral head and abdomen surface without color pattern, 19–24 large brown blotches irregularly distributed on dorsal and lateral body, connected or unconnected to longitudinal black stripe on lateral line. Two irregular spots on caudal fin base, gills, and below margin of eyes with shimmering gold color. Fin membrane hyaline. In formalin-fixed specimens, body is faded and off-white with dark gray spots on the body surface (Fig. 2 A View Figure 2 ).

Distribution and habitat.

Yunnanilus mentibarbatus sp. nov. is currently known only from a stream of the Nanpanjiang River in Jiuxiang Village, Yiliang County, Kunming City, Yunnan Province, China (Fig. 3 A View Figure 3 ). The species inhabits deep pools in caves and streams outside caves at depths ranging from 0.5 to 3 meters (Fig. 3 A View Figure 3 ). New species distribution spans both within the cave and the adjacent surface streams outside the cave. The stream’s flow is slow, and there are water plants in the stream outside the cave. Females are in reproductive season, gonadal stage 2–3, with small spawns in the abdominal cavity. Absence of fleshy projections at the genitalia of females, the fact that only females are harvested, and associated decrease in the number of males during the reproductive season. Other species present in the streamlet include Pseudorasbora parva , Rhinogobius giurinus , Rhodeus ocellatus , and Schistura fasciolata .

Genetic comparisons.

The BI and ML trees exhibit similar topologies, with the numbers above the branch representing Bayesian posterior probabilities from BI and bootstrap support values from ML, respectively. Within Yunnanilus , the species are broadly divided into two clades: Eonemachilus and Y. yangi He et al. 2024 , form one clade, while the new species clusters with other analyzed Yunnanilus species in a separate clade. In addition, Yunnanilus mentibarbatus sp. nov. forms a sister group to Y. jiuchiensis Du, Hou, Chen & Yang, 2018 (Fig. 4 View Figure 4 ). The uncorrected p - distances of the COI and Cyt b genes between Yunnanilus mentibarbatus sp. nov. and the other seven species ranged from 8.40 % to 11.71 %. The maximum and minimum uncorrected p - distances were found between Y. mentibarbatus sp. nov. and Y. yangi (11.71 %) and between Y. analis Yang, 1990 , and Y. pleurotaenia Regan, 1904 (0.41 %), respectively (Table 4 View Table 4 ).

Comparative materials

All specimens for comparison are as follows:

Y. analis : KIZ 1960000625 –26, 2 ex., 37.7–50.2 mm SL, Xingyun Lake, Yuxi City, Yunnan, China.

Y. beipanjiangensis : 91007016, holotype, 47.6 mm SL, 91007017, paratypes, 1 ex., 46.1 mm SL, 91007001–09, 9 ex., 40.5–73.2 mm SL, Luoshuidong, Xintun, Zhanyi District, Yunnan, China.

Y. chui : KIZ 1989001596 , paratypes, 1 ex., 36.1 mm SL, Fuxian Lake, Yuxi, Yunnan, China.

Y. discoloris : KIZ 1983000938 –42, 5 ex., 24.0– 32.9 mm SL, Bailongtan, Chenggong District, Kunming, Yunnan, China.

Y. longibulla : KIZ 1981002383 , holotype, 40.9 mm SL, KIZ 1981002384 –86, KIZ 1981002388 –93, paratypes, 9 ex., 28.5–40.9 mm SL, Yongsheng, Lijiang, Yunnan Province, China.

Y. jiuchiensis : KIZ 2018000002 , holotype, 35.3 mm SL, KIZ 2018000001 , KIZ 2018000003 –09, paratypes, 8 ex., 29.5–37.4 mm SL, Jiuchi County, Pengzhou City, Sichuan Province, China.

Y. macrogaster : KIZ 1980004273 , holotype, 70.1 mm SL, KIZ 1980004274 , paratypes, 1 ex., 70.0 mm SL, Luoping County, Yunnan, China.

Y. macrolepis : 9509001, 9509003, 9506997, paratypes, 3 ex., 63.1–83.8 mm SL, Luoping County, Yunnan, China.

Y. nanpanjiangensis : 9191108, 9191113–14, 191122, 191129, 191134, paratypes, 6 ex., 50.5–67.3 mm SL, Luoping County, Yunnan, China.

Y. paludosus : KIZ 1980001277 –81, paratypes, 5 ex., 56.7–74.3 mm SL, Luoping County, Yunnan, China.

Y. parvus : KIZ 1984001244 , KIZ 1984001246 , KIZ 1984001248 , KIZ 1984001251 –53, paratypes, 7 ex., 25.0– 33.5 mm SL, Nanjian, Kaiyuan City, Yunnan, China.

Y. pleurotaenia : KIZ 2000400050 , KIZ 2000400053 –54, KIZ 2000400061 , KIZ 2000400063 , KIZ 2000400069 , KIZ 2000400071 –72, KIZ 2000400074 , 9 ex., 41.8–63.3 mm SL, Qinglongtan, Dabanqiao, Kunming City, Yunnan Province, China. KIZ 2007003946 , 1 ex., 54.9 mm SL, Baiyukou, Dianchi Lake, Kunming City, Yunnan Province, China.

Y. polylepis : KIZ 2023000009 , holotype, 43.7 mm SL, KIZ 2023000010 –14, KIZ 2023000039 –40, paratypes, 7 ex., 31.9–37.1 mm SL, Qixitan Park, Panxi Town, Huaning County, Yuxi City, Yunnan, China.

Y. spanisbripes : KIZ 199504007 , KIZ 199309023 , KIZ 19920703001 –7, KIZ 200306011 , 10 ex., 51.2–71.9 mm SL, Niulanjiang, Deze Township, Zhanyi District, Qujing, Yunnan, China.

Y. triangulus : KIZ 2018002410 , holotype, 51.8 mm SL, KIZ 2018002404 –09, 2411, paratypes, 7 ex., 37.1–54.6 mm SL, Dalongtan Spring, Wangma Village, Huaning County, Yuxi City, Yunnan, China.

Other characteristic information about Y. chuanheensis , Y. elakatis , Y. forkicaudalis , Y. macrositanus , Y. sichuanensis , and Y. yangi was obtained from their original descriptions.