Oreonectes qinae (Teleostei, Cypriniformes, Nemacheilidae), a new loach species from Guangxi, China

365 Oreonectes qinae (Teleostei, Cypriniformes, Nemacheilidae), a new loach species from Guangxi, China Zhuo-Ni Chen1,2 , Cai-Huan Mo1,2, Li-Na Du1,2 , Li-Na Zhang3 1 Key Laboratory of Ecology of Rare and Endangered Species and Environmental Protection (Guangxi Normal University), Ministry of Education, Guilin, Guangxi 541004, China 2 Guangxi Key Laboratory of Rare and Endangered Animal Ecology, College of Life Sciences, Guangxi Normal University, Guilin, Guangxi 541004, China 2 Forest Resources and Ecological Environment Monitoring Center of Guangxi Zhuang Autonomous Region, Nanning, Guangxi 530022, China Corresponding authors: Li-Na Du ([email protected]); Li-Na Zhang ([email protected]) Copyright: © Zhuo-Ni Chen et al. This is an open access article distributed under terms of the Creative Commons Attribution License (Attribution 4.0 International – CC BY 4.0). Research Article Abstract A new species of loach, Oreonectes qinae sp. nov., was collected in December 2024 from Guangxi Gutingshan Forest Park, Liuzhou City, Guangxi Zhuang Autonomous Region, China. The new species can be distinguished from all other congeners by a suite of morphological characters, including a dorsal-fin origin posterior to the pelvic-fin origin, a degenerated posterior chamber of the swim bladder, and an incomplete lateral line, with 11–13 lateral-line pores. Phylogenetic analysis based on mitochondrial cytochrome b (Cytb) gene sequences confirmed its separation, with uncorrected p-distances ranging from 1.4% to 8.7% compared to closely related species. The discovery of Oreonectes qinae sp. nov. reflects the hidden diversity within Oreonectes in the complex karst landscapes of Guangxi and emphasizes the need for further investigation and conservation of these cryptic freshwater species. Key words: Cavefish, cryptic species, Cytb, karst, Liujiang River, mitochondrial gene, Oreonectes, subterranean, taxonomy Introduction The genus Oreonectes Günther, 1868 includes a group of loaches predominantly distributed across southwestern China, including Guangxi Zhuang Autonomous Region, Guangdong, and Hong Kong, as well as Quang Ninh Province in northern Vietnam (Zheng 1981; Zhu and Cao 1987; Zhu 1989; Lan et al. 1995; Kottelat 2001; Zhong et al. 2024). Established with Oreonectes platycephalus Günther, 1868 as the type species, the genus is morphologically characterized by a flattened head; anterior and posterior nostrils separated by a distance shorter than the diameter of the posterior nostril; anterior nostril elongated into a barbel-like projection exceeding the nostril tube depth; longitudinal black stripe extending from the upper margin of the gill opening or dorsal fin to the middle of the caudal-fin base; six to seven branched dorsal-fin rays; rounded caudal fin; caudal peduncle elongated and narrow; and having an epural in the caudal skeleton (Günther 1868; Sawada 1982; Zhu and Cao 1987; Du et al. 2008; Prokofiev 2010). Academic editor: Tihomir Stefanov Received: 9 May 2025 Accepted: 8 September 2025 Published: 15 October 2025 ZooBank: https://zoobank. org/49729EA9-FB82-4D5A-A519B06DA5A883C4 Citation: Chen Z-N, Mo C-H, Du L-N, Zhang L-N (2025) Oreonectes qinae (Teleostei, Cypriniformes, Nemacheilidae), a new loach species from Guangxi, China. ZooKeys 1255: 365–377. https://doi.org/10.3897/ zookeys.1255.158447 ZooKeys 1255: 365–377 (2025) DOI: 10.3897/zookeys.1255.158447 366 ZooKeys 1255: 365–377 (2025), DOI: 10.3897/zookeys.1255.158447 Zhuo-Ni Chen et al.: A new species of Oreonectes Rapid tectonic uplift associated with the eastern Tibetan Plateau (Su et al. 2019a; Spicer et al. 2021) has dramatically altered the geomorphology of southwestern China, fragmenting subterranean habitats and generating isolated aquatic systems nested within intricate karst networks (Chen and Yu 1985). These environmental shifts promoted allopatric speciation, while intermittent surface water connectivity permitted episodic gene flow and secondary contact among populations (Luo et al. 2021; Wen et al. 2022). Within this context, Oreonectes species have largely specialized for life in underground rivers and surface streams within the karst region of southwestern China (Huang et al. 2009; Liu et al. 2019). Several taxa, including O. polystigmus Du, Chen & Yang, 2008, O. guananensis Yang, Wei, Lan & Yang, 2011, O. luochengensis Yang, Wu, Wei & Yang, 2011, and O. andongensis Luo, Du, Yang & Luo, 2024, have been collected from cave environments; while others, such as O. platycephalus, O. guilinensis Huang, Yang, Wu & Zhou, 2020, O. damingshanensis Yu, Luo, Lan, Xiao & Zhou, 2023, O. zhangi Zhong, Yang, Mo & Chen, 2024, and O. yuedongensis Luo, Lan, Xiao & Zhou, 2024, mainly inhabit surface freshwater rivers or streams. Although O. platycephalus was once considered widespread in Guangxi and Guangdong, integrative morphological and molecular analyses have revealed the presence of several cryptic species within this assemblage (Lan et al. 2024). Newly delineated species, such as O. damingshanensis (Xijiang River, Guangxi), O. zhangi (Nanliujiang, Guangxi), and O. yuedongensis (Pearl River, Guangdong), highlight significant hidden diversity within the genus (Zhu 1989; Du et al. 2008; Huang et al. 2020; Yu et al. 2023; Lan et al. 2024; Luo et al. 2024; Zhong et al. 2024). This high cryptic species diversity is likely due to the fragmented karst landscapes, combined with the limited dispersal capacities of benthic freshwater fish, promoting geographic isolation and genetic divergence among populations (Luo et al. 2021; Wen et al. 2022; Lan et al. 2024). At present, nine species of Oreonectes are recognized, including O. platycephalus, O. polystigmus, O. guananensis, O. luochengensis, O. guilinensis, O. damingshanensis, O. andongensis, O. zhangi, and O. yuedongensis. In December 2024, 14 specimens were collected from small tributary streams in the Gutingshan Forest Park, Youfeng District, Liuzhou City, Guangxi Zhuang Autonomous Region, China. Based on a combination of morphological and molecular evidence, these specimens were determined to represent a previously unrecognized species of Oreonectes. This study provides a comprehensive morphological description of the new species and comparative analyses with its congeners, contributing to a deeper understanding of the biodiversity and evolutionary history of Oreonectes in the karst ecosystems of southern China. Material and methods All experimental procedures complied with the Implementation Rules of the Fisheries Law of the People’s Republic of China and the Laboratory Animal Guidelines for the Ethical Review of Animal Welfare (GB/T 35892–2018). Fourteen type specimens were deposited in the Kunming Natural History Museum of Zoology, Kunming Institute of Zoology (KIZ), Chinese Academy of Sciences (CAS). Among them, six specimens were preserved in 10% formalin, while eight specimens were preserved in 99% ethanol. For DNA extraction, the right pelvic fin of each individual was removed, preserved in 99% ethanol, and stored in a −20 °C freezer. Morphological data were measured point-to-point with a vernier 367 ZooKeys 1255: 365–377 (2025), DOI: 10.3897/zookeys.1255.158447 Zhuo-Ni Chen et al.: A new species of Oreonectes caliper (accuracy of 0.1 mm), following the measurement protocols outlined by Kottelat (1990). Measurements were recorded from the left side of each specimen and processed using Microsoft Excel. Standard abbreviations include SL (standard length), TL (total length), and HL (lateral head length). Genomic DNA was extracted from ethanol-preserved fin tissues using a DNA extraction kit (Sangon Biotech (Shanghai) Co., Ltd., China). The mitochondrial cytochrome b (Cytb) gene was amplified using the primer pair F14724 (5’-GACTTGAAAAACCACCGTTG-3’) and R15915 (5’-CTCCGATCTCCGGATTACAAGAC-3’) following the protocols of Xiao et al. (2001). Polymerase chain reactions (PCR) were carried out in a 25 µL reaction volume with the following cycling conditions: an initial denaturing step at 98 °C for 3 min, 37 cycles of denaturing at 98 °C for 10 s, annealing at 55 °C for 15 s and extending at 72 °C for 15 s, and a final extension at 72 °C for 5 min. Sequencing of amplified products was performed by Sangon Biotech (Shanghai) Co., Ltd (China). Uncorrected p-distances were calculated using the Kimura2-parameter (K2-P) model and 1000 bootstrap replicates in MEGA v. 7.0 (Kumar et al. 2016), based on the Cytb gene. Two-way sequence reads were assembled and refined using SeqMan in DNAStar, while other sequences were downloaded from GenBank, with sequence alignment performed in MEGA v. 11.0 (Tamura et al. 2021). The newly generated sequences were deposited in GenBank (Accession Nos. PV266529–PV266532). The phylogenetic position of Oreonectes qinae sp. nov. was inferred using Bayesian inference (BI) methods, implemented via the CIPRES Science Gateway (Miller et al. 2010). BI analysis was conducted using MrBayes in XSEDE v. 3.2.7a (Ronquist et al. 2012), employing two runs and four Markov chains starting from a random tree. Chains were run for seven million generations and sampled every 100 generations, with the first 25% of sampled trees discarded as burn-in. The optimal nucleotide substitution model for Cytb was determined under the AICc criterion, using PartitionFinder v. 2.1.1, identified as GTR+I+G. The remaining trees were used to construct a consensus tree and estimate Bayesian posterior probabilities (BPPs). The constructed phylogenetic trees were viewed and edited using FigTree v. 1.4.4 (Rambaut 2009). Results Taxonomy Oreonectes qinae Chen, Mo, Zhang & Du, sp. nov. https://zoobank.org/9FF0EFA1-192D-45F7-A439-7D3E06679A07 Tables 1, 2, Figs 1–4 Type material. Holotype • KIZ2024010559, holotype, 78.6 mm SL, female; China: Guangxi Zhuang Autonomous Region: Gutingshan Forest Park, Youfeng District, Liuzhou City, Liujiang River, 24.32325°N, 109.51695°E; collected by Z.S. Qin and Y. Cai, December 2024. Paratypes • KIZ2024010560–563, four specimens, 46.3–70.5 mm SL, female; KIZ2024010564, 52.1 mm SL, male, data same as holotype. Other materials. • KIZ2024010565–571, eight specimens, 30.2–40.0 mm SL, preserved in 99% ethanol for molecular study, data same as the type specimens. 368 ZooKeys 1255: 365–377 (2025), DOI: 10.3897/zookeys.1255.158447 Zhuo-Ni Chen et al.: A new species of Oreonectes Etymology. The species name, qinae, is in recognition of the contributions of Zi-Shan Qin to the collection of the present specimens and dedicated efforts in fieldwork. We suggest the Chinese vernacular name “覃氏岭鳅”. Diagnosis. This new species can be distinguished from all known species of Oreonectes by a combination of the following characteristics: color pattern present; swim bladder degenerated; black longitudinal stripe from posterior upper pectoral fin to caudal-fin base; dorsal-fin origin posterior to pelvic-fin origin; tip of pelvic fin not reaching anus; caudal fin with irregular black markings; caudal fin rounded; maxillary barbel not reaching posterior margin of Table 1. Morphometric and meristic data of Oreonectes qinae sp. nov. Characters Holotype (female) Paratypes (mean ± SD) Females (N = 11) Males (N = 2) Total length (mm) 97.9 34.9–87.2 (58.2 ± 22.5) 38.7–63.9 (51.3 ± 17.8) Standard length (mm) 77.0 28.1–69.4 (46.3 ± 17.3) 30.9–52.4 (41.7 ± 15.2) Percentage of standard length (%) Deepest body depth 17.5 11.0–16.4 (14.3 ± 1.6) 13.1–13.3 (13.2 ± 0.1) Body width 15.5 7.8–15.8 (11.1 ± 3.0) 7.3–12.1 (9.7 ± 3.4) Head width 17.0 14.6–16.3 (15.5 ± 0.7) 13.6–15.7 (14.7 ± 1.5) Head depth 11.8 10.5–12.3 (11.4 ± 0.5) 10.6–10.8 (10.7 ± 0.1) Head length 23.4 22.6–25.1 (23.9 ± 0.7) 21.8–24.3 (23.0 ± 1.7) Predorsal length 62.7 60.0–63.9 (62.3 ± 1.1) 59.7–61.4 (60.5 ± 1.2) Preventral length 53.4 51.5–56.4 (54.4 ± 1.5) 51.0–51.5 (51.3 ± 0.3) Preanal length 77.9 77.6–80.4 (79.2 ± 1.0) 78.1–81.6 (79.9 ± 2.4) Preanus length 72.9 70.6–74.1 (72.6 ± 1.2) 71.0–71.8 (71.4 ± 0.5) Pectoral-fin length 19.5 17.1–21.0 (19.2 ± 1.1) 18.0–19.7 (18.8 ± 1.2) Distance between pectoral fin and pelvic fin 30.7 27.1–33.8 (30.2 ± 2.1) 27.0–30.9 (28.9 ± 2.7) Pelvic-fin length 17.0 15.5–18.0 (17.1 ± 0.8) 16.9–20.9 (18.9 ± 2.8) Distance between pelvic fin and anal fin 24.4 21.7–26.7 (25.1 ± 1.4) 27.3–29.8 (28.6 ± 1.7) Caudal-peduncle length 13.6 10.7–15.2 (13.1 ± 1.0) 12.2–13.3 (12.7 ± 0.7) Caudal-peduncle depth 12.8 10.1–12.8 (11.2 ± 0.9) 10.9–11.2 (11.0 ± 0.2) Percentage of lateral head length (%) Eye diameter 16.0 13.0–22.5 (18.3 ± 3.2) 17.9–18.7 (18.3 ± 0.5) Interorbital width 45.8 36.7–46.4 (40.3 ± 3.5) 37.8–41.7 (39.8 ± 2.7) Postorbital length 54.3 50.6–55.3 (53.3 ± 1.6) 48.7–49.9 (49.3 ± 0.8) Snout length 30.3 30.1–36.1 (32.5 ± 2.0) 33.7–37.9 (35.8 ± 2.9) Percentage of caudal-peduncle length (%) Caudal-peduncle depth 93.9 76.0–99.4 (86.5 ± 8.6) 84.5–89.1 (86.8 ± 3.2) Counts Dorsal-fin rays 3, 7 3, 7–8 3, 7 Pectoral-fin rays 2, 9 2, 9–10 2, 10 Pelvic-fin rays 2, 6 2, 6–7 2, 7 Anal-fin rays 3, 5 3, 5 3, 5 Branched caudal-fin rays 16 16 16 369 ZooKeys 1255: 365–377 (2025), DOI: 10.3897/zookeys.1255.158447 Zhuo-Ni Chen et al.: A new species of Oreonectes opercula; without dark brown V-shaped marking on dorsal surface of head; 16 branched caudal-fin rays; and 12 inner-gill rakers on first gill arch. Description. The morphometric and meristic data of Oreonectes qinae sp. nov. are provided in Table 1. Body elongated and cylindrical (Fig. 1A), slight elevation of head-dorsal junction, deepest body depth 13.2%–19.8% of SL, deepest body depth anterior to dorsal-fin origin, decreasing depth from dorsal-fin origin to caudal-fin base, dorsal-fin origin closer to the posterior margin of the operculum than to caudal-fin base. Head flattened, head width longer than height, head width 60.9%–72.6% of HL, head height 43.5%–54.5% of HL. Whole body covered by scales, except head and thorax. Dorsum of head and above lateral line dark gray. Lighter color below lateral line and abdomen, without body color spots. Mouth inferior, curved, processus dentiformis absent, jaws completely covered by lips (Fig. 1H), snout length shorter than postorbital length of head, visible wrinkles present on surface of lip, lower lip with V-shaped median notch completely interrupted by longitudinal groove (Fig. 1C). Anterior and posterior nostrils closely adjacent, base of anterior nostril tubular, tip elongated to whisker-like, nostril barbel length 90.4%–140.2% of eye diameter. Three pairs of barbels, well-developed, inner rostral barbel length 30.2%– 39.1% of HL, reaching anterior nostril; outer rostral barbel length 47.3%–57.3% of HL, extending to posterior margin of eye; maxillary barbel length 40.8%– 50.9% of HL, not reaching posterior margin of opercula. Eyes normal, interorbital width greater than eye diameter, eye diameter 13.0%–22.5% of HL. Tip of pelvic fin close to, but not reaching, anus (Fig. 1). Dorsal-fin origin posterior to pelvic-fin origin. Distance between anus and tip of anal fin 0.9–2.0 times eye diameter. Caudal fin rounded. Caudal-peduncle length greater than width, caudal-peduncle depth 76.0%–99.4% of length, adipose crests along both dorsal and ventral sides absent. Three unbranched and seven to eight branched dorsal-fin rays, dorsal-fin rays dark, membrane transparent and scattered with black pigments, two unbranched and nine to 10 branched pectoral-fin rays, two unbranched and six to seven branched pelvic-fin rays, three unbranched and five branched anal-fin rays, 16 branched caudal-fin rays. Inner-gill rakers on first gill arch 12 (2). Cephalic lateral-line system well-developed, 9–10+4 infraorbital pores, 7–8 supraorbital canal pores, six supratemporal canal pores, 9–10 preoperculo-mandibular canal Table 2. Uncorrected p-distances (%) between 10 Oreonectes species based on cytochrome b (Cytb). ID Species 1 2 3 4 5 6 7 8 9 1Oreonectes qinae sp. nov. 2Oreonectes andongensis 5.5 3Oreonectes damingshanensis 1.4 6.8 4Oreonectes guilinensis 6.9 6.9 7.2 5Oreonectes guananensis 8.7 7.0 8.6 8.8 6Oreonectes luochengensis 7.4 6.2 7.5 8.1 3.5 7Oreonectes platycephalus 2.2 3.9 2.0 2.0 5.6 4.9 8Oreonectes polystigmus 5.9 5.3 5.7 7.1 6.1 6.0 3.6 9Oreonectes yuedongensis 5.0 5.2 5.6 4.8 6.8 6.2 2.6 4.9 10 Oreonectes zhangi 4.5 6.8 4.2 7.3 9.0 7.2 3.5 6.3 5.4 370 ZooKeys 1255: 365–377 (2025), DOI: 10.3897/zookeys.1255.158447 Zhuo-Ni Chen et al.: A new species of Oreonectes Figure 1. Oreonectes qinae sp. nov. A–C. Lateral, dorsal, and ventral views of holotype KIZ20240559 (♀); D. Live photo of female, photo by Zhou Jia-Jun; E–G. Lateral, dorsal, and ventral views of paratype KIZ20240564 (♂); H. Ventral view of head of holotype KIZ20240559 (♀) I. Photo of the gill rakers. Figure 2. Morphological characteristics of paratype KIZ20240563 (♂) of Oreonectes qinae sp. nov., stomach and intestine (A); Anterior and posterior chambers (B). 371 ZooKeys 1255: 365–377 (2025), DOI: 10.3897/zookeys.1255.158447 Zhuo-Ni Chen et al.: A new species of Oreonectes pores. Lateral line incomplete, with 11–13 lateral-line pores, last lateral-line pore not reaching tip of pectoral fin. Posterior chamber of swim bladder degenerated, only 1.5 times eye diameter (Fig. 2A). Stomach U-shaped, intestine curved along stomach, leading directly to anus (Fig. 2B). Genetic comparisons. BI analysis based on 1116 bp of Cytb sequences produced consistent topologies. The phylogenetic reconstruction confirmed the validity of the new species, with high nodal support (BPP ≥ 0.95). All Oreonectes species formed a well-supported monophyletic group, phylogenetically resolved as the sister lineage to the clade containing Guinemachilus and Micronemacheilus. Oreonectes qinae sp. nov. formed a highly supported clade with O. damingshanensis and O. zhangi (Fig. 3). Uncorrected p-distances based on Cytb between Oreonectes qinae sp. nov. and the nine other species ranged from 1.4% (O. damingshanensis) to 8.7% (O. guananensis) (Table 2). Sexual dimorphism. Mature males with genital papilla positioned immediately posterior to anus; gonopore opening at tip of fleshy prominence (Fig. 1G); feature absent in females (Fig. 1C). Females generally larger than males, with Figure 3. Bayesian phylogram of Oreonectes based on cytochrome b (Cytb) sequences. Numbers on branches represent BPPs from BI. 0.05 ON116508 ON116516 OQ754110 ON116504 ON116530 PP590242 ON116496 MW729320 AP012142 MN239094 OR188128 ON116518 NC039380 MW532080 MW043720 ON116512 ON116493 ON116495 KT943751 OQ754121 ON116513 ON116507 OQ754117 NC073134 OQ754123 NC073144 OQ754124 ON116517 ON116514 PV266531 DQ105197 NC004696 OQ754118 ON116520 PV266530 MW192447 NC073128 PV266529 OQ754111 PP601248 NC027662 NC073127 NC073129 OR712241 PV266532 OR712240 OQ754116 ON116515 PP601247 MT845213 0.53 0.96 0.93 0.99 0.99 0.99 0.99 0.96 0.96 0.98 Triplophysa tianeensis Triplophysa macrocephala Traccatichthys zispi Traccatichthys pulcher Lefua echigonia Lefua costata Lefua nikkonis Yunnanilus jiuchiensis Yunnanilus pleurotaenia Yunnanilus analis Paranemachilus jinxiensis Paranemachilus genilepis Paranemachilus zhengbaoshani Paranemachilus pingguoensis Troglonectes shuilongensis Troglonectes furcocaudalis Troglonectes macrolepis Troglonectes microphthalmus Karstsinnectes acridorsalis Karstsinnectes parva Karstsinnectes anophthalmus Guinemachilus bailianensis Guinemachilus longibarbatus Micronemacheilus cruciatus Micronemacheilus pulcherrimus Oreonectes guananensis Oreonectes guananensis Oreonectes luochengensis Oreonectes luochengensis Oreonectes andongensis Oreonectes andongensis Oreonectes andongensis Oreonrctes yuedongensis Oreonrctes yuedongensis Oreonectes polystigmus Oreonectes polystigmus Oreonrctes yuedongensis OQ754112 Oreonrctes guilinensis Oreonrctes platycephalus Oreonrctes platycephalus Oreonrctes zhangi Oreonrctes zhangi Oreonrctes zhangi Oreonrctes damingshanensis Oreonrctes qinae Oreonrctes damingshanensis Oreonrctes damingshanensis Oreonrctes qinae Oreonrctes qinae Oreonrctes qinae sp. nov. sp. nov. sp. nov. sp. nov. JF340409 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 0.97 1.00 1.00 Triplophysa panzhouensis Oreonrctes damingshanensis 0.74 372 ZooKeys 1255: 365–377 (2025), DOI: 10.3897/zookeys.1255.158447 Zhuo-Ni Chen et al.: A new species of Oreonectes pelvic-fin length measuring 17.33% of SL in female KIZ2024010559 vs. 16.9% in male KIZ2024010564. Coloration. Dorsum of head and above lateral line dark gray. Lighter color below lateral line and abdomen, without body color spots. In both sexes, distinct black stripe extending from lateral line to caudal-fin base; caudal-fin base black. In life, body dark gray except abdomen pinkish; small black spots covering body except on abdomen; no irregular spots (Fig. 1D). Dorsal fin with black pigments on fin membrane. In formalin-fixed specimens, body color, black spots, and stripe somewhat faded, dark gray above head and lateral line, light color below lateral line, abdomen white (Fig. 1A–C, E–G). Distribution and habitat. Oreonectes qinae sp. nov. is currently only known from Gutingshan Forest Park, Youfeng District, Liuzhou City, Guangxi Zhuang Autonomous Region, China, in the Liujiang River drainage (24.32325°N, 109.51695°E) (Fig. 4A). The species inhabits small streamlets with water depths ranging from 0.5 to 1.5 m, characterized by rocky substrate and abundant macrophyte growth, providing suitable habitat conditions (Fig. 4B). Other aquatic species observed in the same streamlet include the crab Qianguimon splendidum Huang, 2018, and the shrimp Caridina huananensis Liang, 2004; there is no other fish in the habitat. Discussion The distinct phylogenetic placement of Oreonectes qinae sp. nov., supported by an uncorrected p-distance of 1.4% from O. damingshanensis and 4.5% from O. zhangi, combined with clear morphological differentiation, substantiates its recognition as a valid species. Currently, the genus Oreonectes comprises 10 described species, including the newly identified species. Species of Oreonectes are primarily distributed in the Nanliujiang River (O. zhangi) and the Pearl River (O. andongensis, O. damingshanensis, O. guananensis, O. guilinensis, O. luochengensis, O. platycephalus, O. polystigmus, Oreonectes qinae sp. nov., and O. yuedongensis), with records spanning Guangxi, Guangdong, Hong Kong, and Quang Ninh Province in northern Figure 4. Distribution of Oreonectes qinae sp. nov. in Guangxi, China (A); Habitat photo of type locality at time of collection (B). 373 ZooKeys 1255: 365–377 (2025), DOI: 10.3897/zookeys.1255.158447 Zhuo-Ni Chen et al.: A new species of Oreonectes Vietnam (Günther 1868; Kottelat 2001; Du et al. 2008; Yang et al. 2011a; Yang et al. 2011b; Huang et al. 2020; Yu et al. 2023; Luo et al. 2024; Zhong et al. 2024; Lan et al. 2024). Within the genus, O. damingshanensis, O. platycephalus, O. qinae sp. nov., and O. zhangi are characterized by a degenerated swim bladder, while O. andongensis, O. guananensis O. guilinensis, and O. luochengensis are characterized by a well-developed swim bladder. Therefore, O. qinae sp. nov. can be distinguished by its swim bladder morphology from other congeners, except for O. damingshanensis, O. platycephalus, and O. zhangi. However, O. qinae sp. nov. can be readily distinguished from O. damingshanensis (sister species on phylogenetic trees, p-distances 1.4% with new species) by 16 branched caudal-fin rays (vs. 14), 11–13 lateral-line pores, last pore not reaching tip of pectoral fin (vs. 14–15 lateral-line pores, last reaching above tip of pectoral fin), 12 inner-gill rakers on first gill arch (vs. nine), without irregular black spots present on dorsal and lateral surfaces (vs. irregular black spots present on dorsal and lateral surfaces), a short tube connected two chamber of air-bladder (vs. a long and slender tube), and the new species is primarily found in Liuzhou City, Guangxi, belonging to the Liujiang River basin of the Pearl River system (Nanning City, Guangxi, belonging to the Hongshuihe River basin of the Pearl River system), Although the two species share only 1.4% genetic divergence, their pronounced morphological disparity and distinct geographic ranges provide unequivocal evidence for their recognition as separate species. A comparable pattern is observed in Traccatichthys pulcher Nichols & Pope, 1927 and Traccatichthys taeniatus Pellegrin & Chevey, 1936, which exhibit a low genetic distance of 1.58% (Qin et al. 2025). Compared with congeners characterized by a degenerated swim bladder, Oreonectes qinae sp. nov. can be distinguished from O. platycephalus by 16 branched caudal-fin rays (vs. 14–15), black longitudinal stripe from posterior upper pectoral fin to caudal-fin base (vs. short black stripe), and head width 60.9%–72.6% of HL (vs. 79.0%–84.6%); from O. zhangi by the tip of the pelvic fin not reaching anus (vs. surpassing), a black longitudinal stripe from posterior upper pectoral fin to caudal-fin base (vs. short black stripe), 12 inner-gill rakers on first gill arch (vs. nine), head length 21.8%–25.1% of SL (vs. 18.6%– 20.2%), predorsal length 59.7%–63.9% of SL (vs. 56.2%–59.4%), prepelvic length 51.0%–56.4% of SL (vs. 48.1%–50.8%), preanal length 77.6%–81.6% of SL (vs. 67.7%–72.1%), snout length 30.1%–37.9% of HL (vs. 38.2%–48.8%), and postorbital length 48.7%–55.3% of HL (vs. 43.0%–47.9%). All morphological and molecular evidence supported the validity of the new species. The presence of oocytes in the abdominal cavities of female specimens indicated that individuals of Oreonectes qinae sp. nov. were undergoing active reproductive development at the time of collection. Among the known species of Oreonectes, except the four species collected in caves, those collected from surface streams, including O. damingshanensis and O. zhangi in February, O. platycephalus in April, O. guilinensis in May, O. yuedongensis in July, and Oreonectes qinae sp. nov. in December, were either in the reproductive phase or approaching it. The nutritional constraints of karst cave ecosystems, characterized by limited food availability, impose significant challenges for sustaining the metabolic demands associated with reproduction (Chen et al. 1994). Based on the present findings, we propose that species of Oreonectes predominantly inhabit subterranean environments or in comparable