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Research Article
Description of a new troglobitic Sinocyclocheilus (Pisces, Cyprinidae) species from the upper Yangtze River Basin in Guizhou, South China
expand article infoWei-Han Shao‡, Guang-Yuan Cheng§, Xiao-Long Lu|, Jia-Jun Zhou#, Zhi-Xuan Zeng¤
‡ Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, China
§ Guiyang Bureau of Ecology and Environment, Guiyang, China
| Guiyang Qianren Ecological Conservation Center, Guiyang, China
¶ Zhejiang Forest Resource Monitoring Center, Hangzhou, China
# Zhejiang Forestry Survey Planning and Design Company Limited, Hangzhou, China
¤ Huazhong University of Science and Technology, Wuhan, China

Corresponding author: Jia-Jun Zhou ( cnwaters@foxmail.com )

Corresponding author: Zhi-Xuan Zeng ( 985801524@qq.com )

Academic editor: Nicolas Hubert
© 2024 Wei-Han Shao, Guang-Yuan Cheng, Xiao-Long Lu, Jia-Jun Zhou, Zhi-Xuan Zeng.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation: Shao W-H, Cheng G-Y, Lu X-L, Zhou J-J, Zeng Z-X (2024) Description of a new troglobitic Sinocyclocheilus (Pisces, Cyprinidae) species from the upper Yangtze River Basin in Guizhou, South China. Zoosystematics and Evolution 100(2): 515-529. https://doi.org/10.3897/zse.100.119520
ZooBank: urn:lsid:zoobank.org:pub:5B410772-DA79-437F-8ABB-A047B4FDC604
Open Access

Abstract

Sinocyclocheilus guiyang, a new troglobitic species from a subterranean tributary of the upper Yangtze Basin in Guiyang City, Guizhou Province, China is described in the present study. The new species is distinguishable from its congeneric species by a combination of the following characters: tip of maxillary barbel reaching to posterior edge of orbit; forehead horn absent; eye absent (or highly reduced) and tip of pectoral fins not significantly extending beyond the base of the pelvic fin. Molecular evidence, based on the mitochondrial cytochrome b (cytb) gene, further supports the validity of the species and also reveals its close relationship with S. cyphotergous, S. multipunctatus, S. punctatus and S. sanxiaensis. In addition, the new species faces a high risk of extinction, underscoring the urgency for habitat protection measures within its limited range.

Key Words

cavefish, conservation, morphology, phylogenetic analysis, Yangtze River

Introduction

Sinocyclocheilus Fang, 1936 (golden-line barbel), endemic to south China, is one of the most diversified genera in the family Cyprinidae, consisting of more than seventy species (Jiang et al. 2019; Mao et al. 2022; Xu et al. 2023; Luo et al. 2024). Highly-developed subterranean river systems in this region are a major contributor to its remarkable diversity because Sinocyclocheilus is restricted to subterranean river systems and adjacent regions (Ma et al. 2019). To date, sixty-six Sinocyclocheilus species are endemic to the Pearl River Basin, with only six species (S. grahami Regan, 1904, S. wumengshanensis Li, Mao & Lu, 2003, S. huizeensis Cheng, Pan, Chen, Li, Ma & Yang, 2015, S. wui Li & Li, 2013, S. sanxiaensis Jiang, Li, Yang & Chang, 2019 and S. multipunctatus Pellegrin, 1931) occurring in the Yangtze River Basin (Eschmeyer et al. 2024). In addition, three of them (S. grahami, S. wumengshanensis and S. huizeensis) are restricted to Yunnan Province which belongs to the Jinshajiang River (a section of the mainstream of upper Yangtze River) System. Only one species, S. multipunctatus, is found in the Wujiang River System, a major southern tributary of the upper Yangtze River in Guizhou Province.

However, similar to the Pearl River Basin, the Wujiang River System also exhibits extensive and well-developed karst landforms (Che and Yu 1985), which has provided good conditions for the formation of subterranean river systems and the subsequent evolution of troglobitic fishes. This can be seen in the high diversity of the hypogean Triplophysa which has five described species within this river system (Liu et al. 2022). Moreover, a recent breakthrough study reported S. sanxiaensis from the Three Gorges Reservoir which belongs to the mainstream of the upper Yangtze River Basin in west Hubei Province. Molecular phylogenetic analysis has grouped S. sanxiaensis with S. cyphotergous Dai, 1988, S. multipunctatus and S. punctatus Lan & Yang, 2017 (Jiang et al. 2019). The S. cyphotergous – S. multipunctatus group, herein defined for the abovementioned four species, is characterised by a typically convex dorsal profile, short barbels and high head depth. For a long time, members of this species group were only mainly known from Hongshui River (a section of the mainstream of the Pearl River) System and Liujiang River (north tributary of the Pearl River) System, with only S. multipunctatus spanning from Hongshui River to Wujiang River (Wu 1989; Zhao and Zhang 2009). The description of S. sanxiaensis greatly expanded the distribution boundary of this species group, providing insights into the potentially underestimated diversity of Sinocyclocheilus in the Wujiang River System, situated between the Three Gorges Reservoir and the Hongshui River.

Various morphological features that are adapted to subterranean environments have been found in troglobitic species of Sinocyclocheilus including degenerated eyes, reduced (or lost) pigmentation, degenerated scales, elongated fins and horn-like structures (e.g. humpback and horn) (Zhao and Zhang 2009; Ma et al. 2019). In addition, possession of extended barbels in Sinocyclocheilus species is common as the long barbels better detect water flow and aid foraging in subterranean water systems which are marked by permanent darkness and food scarcity (Ma et al. 2019). Fewer than one third (twenty-one) of Sinocyclocheilus species have short maxillary barbels that do not extend to the posterior edge of the preoperculum (Zhao and Zhang 2009; Lan et al. 2013; Xu et al. 2023) and more than half possess horn-like structures (e.g. S. anatirostris Lin & Luo, 1986, S. aquihornes Li & Yang, 2007, S. cyphotergous, S. rhinocerous Li & Tao, 1994 and S. longicornus Luo, Xu, Wu, Zhou & Zhou, 2023). Amongst the currently recognised species of Sinocyclocheilus, only two, S. jinxiensis Zheng, Xiu & Yang, 2013 and S. sanxiaensis, possess a combination of short maxillary barbels, degenerated eyes, reduced pigmentation and lack of horn-like structures. These combined characters are unique within Sinocyclocheilus and represent exceptional cases for evolutionary studies.

The authors conducted a fish field survey in a subterranean stream within the Wujiang River System in central Guizhou Province, south China. This survey yielded seven specimens characterised by short maxillary barbels, no horn-like structures and absent or highly reduced eyes, traits shared with S. jinxiensis and S. sanxiaensis. Careful morphological examination revealed that they are, in fact, not conspecific with any other known species of Sinocyclocheilus and, thus, represent an unnamed species. Genetic analyses further revealed that these specimens formed a distinct cluster within the S. cyphotergous – S. multipunctatus group. The purpose of the present paper is to provide a formal description of this unnamed species, based on multiple lines of evidence including morphological and molecular datasets.

Material and methods

Specimen sampling and preservation

The treatment of experimental animals in this study was consistent with the Chinese animal welfare laws (GB/T 35892–2018). Specimens were collected from central-south Guizhou and north Guangxi from 2019 to 2023. After anaesthesia, specimens were fixed in 10% formaldehyde and then preserved in 75% ethanol for morphological comparison. The right pelvic fin of some specimens was dissected and fixed in 95% ethanol for DNA extraction. Specimens newly collected for this study have been deposited in the Institute of Hydrobiology, Chinese Academy of Sciences (IHB), Guangxi University (GXU) and Zhejiang Forest Resource Monitoring Center (ZJFR). Other comparative materials have been stored in Kunming Institute of Zoology, Chinese Academy of Sciences (KIZ).

Morphological analyses

Measurements were taken point-to-point on the left side of the specimens with a Vernier caliper to a precision of 0.1 mm. All measurements, counts and terminologies follow Zhao et al. (2006), with the following exceptions: maxillary barbel in the present study refers to the barbel rooted at the corner of the mouth and rostral barbel refers to the barbel rooted at the rostrum. The major morphometrics are shown in Fig. 1. All morphometric measurements have been transferred to percentage of standard length (SL) and recorded to the closest 0.1%. The caudal peduncle depth (CPD) to caudal peduncle length (CPL) ratios are calculated and recorded to the closest 0.01. For osteological observation, specimens were scanned by micro-computed tomography (micro-CT) (Siemens Somatom Definition X-ray machine). The 3D renderings of the osteological structure of the whole specimen and pharyngeal dentition were created and visualised in VG Studio Max 2.1 (He et al. 2013). Total vertebrae were counted from the first free vertebra to the last half-centrum.

Figure 1. 

Major morphometrics demonstrated on original drawing of Sinocyclocheilus guiyang. standard length (1), head length (2), eye diameter (3), snout length (4), pre-nostril length (5), head depth (6), body depth (7), caudal peduncle depth (8), upper jaw length (a–c), lower jaw length (b–c), pre-pectoral length (a–d), pre-dorsal length (a–f), pre-pelvic length (a–h), pre-anal length (a–m), pectoral-fin base length (d–e), pectoral-fin length (d–g), dorsal-fin length (f–j), dorsal-fin base length (f–l), pelvic-fin base length (h–i), pelvic-fin length (h–k), anal-fin base length (m–n), anal-fin length (m–o), caudal peduncle length (n–p).

Morphometric measurements were subject to principal component analysis (PCA) to explore the relative contributions of specific variables to morphological variations. PCA was conducted on the Statistical Package for the Social Sciences (SPSS) 19.0 (IBM, Armonk, NY, USA). Prior to PCA, all included measurements were normalised by log transformation. Linear regression analysis for origin data of each character was also computed on SPSS 19.0.

DNA extraction, PCR and sequencing

Genomic DNA was extracted from 95% ethanol-fixed fin tissue using the modified salt-extraction method described by Tang et al. (2008). Fragments containing the mitochondrial cytochrome b (cytb) gene were amplified by polymerase chain reaction (PCR) with the primer pairs (L14724 and H15915) (Zhao et al. 2006) in a 30 μl reaction system: 3 μl 10 × PCR buffer, 30–50 ng DNA template, 1 μl primers (each 10 μM), 1.5 μl dNTPs (each 2.5 mM), 2.5 U Taq DNA polymerase and ddH2O added to reach the final volume. PCR procedures also follow Tang et al. (2008). The PCR products were purified and sequenced in both directions with the corresponding primers by a commercial sequencing company. All newly-generated sequences have been submitted to GenBank.

Molecular data analyses

Phylogenetic analysis was performed, based on nine newly-obtained cytb sequences and an additional 47 sequences downloaded from NCBI GenBank, including 49 Sinocyclocheilus species and a single species Cyprinus carpio Linnaeus, 1758 as outgroup (Table 1). The sequences were revised manually and then aligned using ClustalW in MEGA7.0 (Kumar et al. 2016). Both Maximum Likelihood (ML) and Bayesian Inference (BI) methods were utilised to reconstruct the phylogenetic relationship. The optimal nucleotide substitution model was selected in ModelFinder (Kalyaanamoorthy et al. 2017) according to Akaike Information Criterion. Maximum Likelihood analysis was run in IQ-TREE 1.6.8 (Nguyen et al. 2015), with the selected TIM3+F+I+G4 model and 1,000 non-parametric bootstrap replicates. Bayesian Inference was performed in MrBayes 3.2.6 (Ronquist et al. 2012) under the selected GTR+F+I+G4 model, using the MCMC method (four chains simultaneously run for 20,000,000 generations) to calculate posterior probability, with tree sampling frequency set to 1 per 1000 cycles and the initial 25% of the sampled data discarded as burn-in. The convergence of BI analysis was reached when the average standard deviation of split frequencies was less than 0.01. Uncorrected pairwise genetic distances (p-distance), based on cytb, were computed in MEGA 7.0.

Table 1.
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GenBank accession numbers for molecular phylogenetic analysis. n/a, not available.

Taxon Voucher specimen Locality Accession No. Source
Sinocyclocheilus sanxiaensis KIZ 2019000001 Hubei, Yangtze River MN106258 NCBI
Sinocyclocheilus grahami XH0701 Yunnan, Yangtze River AY854694 NCBI
Sinocyclocheilus wumengshanensis YNUSM20160817008 Yunnan, Yangtze River MG021442 NCBI
Sinocyclocheilus guiyang 01 IHB 202012250001 Guizhou, Yangtze River OR141734 This study
Sinocyclocheilus guiyang 02 IHB 202012250002 Guizhou, Yangtze River OR141735 This study
Sinocyclocheilus guiyang 03 IHB 202207260001 Guizhou, Yangtze River OR141736 This study
Sinocyclocheilus multipunctatus 01 IHB 202302080001 Guizhou, Yangtze River OR141737 This study
Sinocyclocheilus multipunctatus 02 n/a Guizhou, Pearl River MG026730 NCBI
Sinocyclocheilus cyphotergous 01 IHB 202302080002 Guizhou, Pearl River OR141738 This study
Sinocyclocheilus cyphotergous 02 IHB 202207280010 Guizhou, Pearl River OR141739 This study
Sinocyclocheilus punctatus 01 ZJFR 2311001 Guangxi, Pearl River PP112594 This study
Sinocyclocheilus punctatus 02 ZJFR 2311004 Guizhou, Pearl River PP112595 This study
Sinocyclocheilus punctatus 03 ZJFR 2312002 Guangxi, Pearl River PP112596 This study
Sinocyclocheilus punctatus 04 GZNU 20150811002 Guizhou, Pearl River MK610341 NCBI
Sinocyclocheilus longibarbus XH2901 Guizhou, Pearl River AY854714 NCBI
Sinocyclocheilus longicornus GZNU 20210503016 Guizhou, Pearl River MZ634123 NCBI
Sinocyclocheilus zhenfengensis GZNU 20150112021 Guizhou, Pearl River MK610342 NCBI
Sinocyclocheilus bicornutus XH8301 Guizhou, Pearl River AY854730 NCBI
Sinocyclocheilus angularis GZNU 202001332 Guizhou, Pearl River MW362289 NCBI
Sinocyclocheilus xingyiensis GZNU SLS202008180 Guizhou, Pearl River ON573221 NCBI
Sinocyclocheilus guanyangensis n/a Guangxi, Pearl River OQ718399 NCBI
Sinocyclocheilus lateristriatus XH1601 Yunnan, Pearl River AY854707 NCBI
Sinocyclocheilus malacopterus XH0901 Yunnan, Pearl River AY854697 NCBI
Sinocyclocheilus angustiporus XH1203 Yunnan, Pearl River AY854702 NCBI
Sinocyclocheilus hyalinus XH4701 Yunnan, Pearl River AY854721 NCBI
Sinocyclocheilus rhinocerous XH3901 Yunnan, Pearl River AY854720 NCBI
Sinocyclocheilus tingi YNUST 201406180002 Yunnan, Pearl River MG323567 NCBI
Sinocyclocheilus guishanensis XH5401 Yunnan, Pearl River AY854722 NCBI
Sinocyclocheilus maculatus n/a Yunnan, Pearl River MF325010 NCBI
Sinocyclocheilus maitianheensis XH2301 Yunnan, Pearl River AY854710 NCBI
Sinocyclocheilus anophthalmus XH3002 Yunnan, Pearl River AY854716 NCBI
Sinocyclocheilus qiubeiensis n/a Yunnan, Pearl River MF324998 NCBI
Sinocyclocheilus qujingensis XH3801 Yunnan, Pearl River AY854719 NCBI
Sinocyclocheilus purpureus IHB 2006637 Yunnan, Pearl River EU366194 NCBI
Sinocyclocheilus lunanensis XH0302 Yunnan, Pearl River AY854686 NCBI
Sinocyclocheilus huaningensis XH3701 Yunnan, Pearl River AY854718 NCBI
Sinocyclocheilus oxycephalus XH0201 Yunnan, Pearl River AY854685 NCBI
Sinocyclocheilus yangzongensis XH6102 Yunnan, Pearl River AY854726 NCBI
Sinocyclocheilus macrocephalus XH0110 Yunnan, Pearl River AY854684 NCBI
Sinocyclocheilus yishanensis n/a Guangxi, Pearl River MK387704 NCBI
Sinocyclocheilus macrophthalmus XH8401 Guangxi, Pearl River AY854733 NCBI
Sinocyclocheilus xunlensis IHB 04050268 Guangxi, Pearl River EU366187 NCBI
Sinocyclocheilus lingyunensis XH0502 Guangxi, Pearl River AY854691 NCBI
Sinocyclocheilus donglanensis ASIZB 94746 Guangxi, Pearl River AB196440 NCBI
Sinocyclocheilus ronganensis n/a Guangxi, Pearl River KX778473 NCBI
Sinocyclocheilus macrolepis XH8201 Guangxi, Pearl River AY854729 NCBI
Sinocyclocheilus anatirostris XH1901 Guangxi, Pearl River AY854708 NCBI
Sinocyclocheilus anshuiensis n/a Guangxi, Pearl River KR069120 NCBI
Sinocyclocheilus microphthalmus XH0402 Guangxi, Pearl River AY854687 NCBI
Sinocyclocheilus tianeensis XH3403 Guangxi, Pearl River AY854717 NCBI
Sinocyclocheilus furcodorsalis XH2202 Guangxi, Pearl River AY854709 NCBI
Sinocyclocheilus altishoulderus XH5801 Guangxi, Pearl River AY854724 NCBI
Sinocyclocheilus jiuxuensis XH8501 Guangxi, Pearl River AY854736 NCBI
Sinocyclocheilus jii XH8101 Guangxi, Pearl River AY854727 NCBI
Sinocyclocheilus yimenensis IHB 2006645 Yunnan, Red River EU366192 NCBI
Cyprinus carpio (outgroup) n/a n/a MK088487 NCBI

Results

Sinocyclocheilus guiyang sp. nov.

https://zoobank.org/67337E27-2D91-4C21-B557-AA36ECABDAA1
Fig. 2, Table 2

Type materal

Holotype. IHB 202012250001, 124.0 mm SL; China: Guizhou Province: Guiyang City: Qingzhen County: a subterranean stream tributary of the Wujiang System in the upper Yangtze River Basin, 26°50'26"N, 106°16'37"E, 1250 m elevation; Jia-Jun Zhou, Dec 2020.

Paratypes. IHB 201911140001, 1 specimen, 57.5 mm SL; Zhi-Xuan Zeng, Nov 2019; other data same as holotype. IHB 202012250002, 1 specimen, 86.4 mm SL; collected with holotype. IHB 202207260001, GXU 202207260002–04, 4 specimens, 124.3–174.1 mm SL; Jia-Jun Zhou, Jul 2022; other data same as holotype.

Diagnosis

Sinocyclocheilus guiyang is distinguishable from all other congeners by a combination of the following characters: tip of maxillary barbel not reaching to posterior edge of preoperculum, horn-like structure in forehead absent, eye absent or highly reduced, pectoral fin not significantly extending beyond base of pelvic fin. The major diagnostic characters for S. guiyang and related species are summarised in Table 3.

Description

Morphometric measurements of type specimens have been transferred to percentage of standard length (SL), as summarised in Table 2. Body laterally compressed; maximum body depth positioned at insertion of dorsal-fin. Dorsal profile convex from snout tip to dorsal-fin base end and slightly concave after dorsal-fin base. Ventral profile of pre-anal part slightly convex and slightly concave after anal-fin origin.

Table 2.
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Morphometric characters of Sinocyclocheilus guiyang.

Character Holotype Holotype + Paratypes (n = 7)
Range Mean SD
Standard length (mm) 124.0 57.5–144.1
In Percentage of SL (%)
Body depth 29.8 26.7–33.1 29.4 2.1
Predorsal length 55.4 53.6–59.6 55.9 2.1
Dorsal-fin base length 16.8 15.3–16.8 15.8 0.8
Dorsal-fin length 18.8 17.6–24.5 20.2 2.2
Pre-anal length 71.4 70.8–75.7 73.2 1.8
Anal-fin base length 9.8 7.5–10.2 9.2 1.0
Anal-fin length 16.6 16.0–18.3 17.1 0.9
Prepectoral length 31.3 30.7–35.7 32.5 1.6
Pectoral-fin base length 4.4 4.0–4.6 4.3 0.2
Pectoral-fin length 21.3 20.8–22.2 21.5 0.5
Prepelvic length 50.6 50.6–55.3 52.9 1.6
Pelvic-fin base length 5.7 4.5–5.7 5.2 0.4
Pelvic-fin length 16.5 15.4–19.8 17.3 1.4
Caudal peduncle length (CPL) 19.5 16.5–20.7 18.5 1.5
Caudal peduncle depth (CPD) 11.8 10.0–13.2 11.2 1.2
Head length 31.5 30.2–34.1 32.2 1.4
Head depth 19.0 16.8–21.0 19.14 1.3
Head width 16.0 10.4–17.6 15.3 2.4
Snout length 10.9 9.9–11.0 10.5 0.5
Eye diameter 3.5 3.5–5.9 4.6 1.2
Interorbital width 10.4 8.3–10.5 9.7 0.8
Prenostril length 5.7 4.5–6.0 5.6 0.5
Width between posterior nostrils 7.2 5.8–7.4 6.6 0.6
Upper jaw length 10.2 10.1–10.3 10.2 0.1
Lower jaw length 9.4 8.9–9.5 9.2 0.2
Mouth width 8.3 6.8–8.3 7.5 0.6
Rostral barbel length 5.2 4.9–7.1 6.2 0.9
Maxillary barbel length 5.9 5.8–8.3 7.1 0.9
CPD to CPL ratio 0.60 0.55–0.67 0.61 0.04
Table 3.
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Major diagnostic characters for Sinocyclocheilus guiyang and its close congeners. n/a, not available.

Characters S. guiyang S. multipunctatus S. punctatus S. sanxiaensis S. jinxiensis S. jiuxuensis S. mashanensis S. brevibarbatus S. yangzongensis
Eye Absent or highly reduced Normal Normal Absent Absent Normal Normal Normal Normal
Tip of maxillary barbel Reaching to posterior edge of orbit Reaching to posterior edge of preoperculum Reaching to anterior edge of orbit Not reaching to anterior edge of orbit Reaching to posterior edge of orbit Reaching or extending to posterior edge of orbit Extending to anterior edge of orbit Not reaching to anterior edge of orbit Extending to anterior edge of orbit
Pectoral-fin extending to pelvic-fin insertion Yes No Yes Yes Yes Yes Yes Yes No
Gill rakers 10 n/a 7–8 7 13–14 8–10 7–9 8–9 8–11
Lateral-line scales 45–47 53–60 48–60 41 38–41 42–51 47–50 49–51 71–81
Degenerated body scales above and below lateral line Yes Yes Yes Yes No Yes Yes Yes Yes
Black blotches on body Absent Present Present Absent Absent Absent Absent Absent Present

Head slightly compressed, conical in lateral view. Eyes absent (5) or highly reduced and partially covered with skin (2). Eye orbits located in dorsal anterior part of head, filled with soft tissue. Nostrils located at midway between snout tip and anterior margin of orbit; anterior nostril with rim forming an oblique tube, posteriorly thickening and elongating; posterior nostril open and elliptical. Snout blunt in dorsal view and slightly pointed in lateral view. Mouth subterminal and arched; with two pairs of barbels; rostral pair positioned anterior to anterior nostril, extending to the insertion of anterior margin of orbit, being 6.2% (4.9–7.1%) of SL; maxillary pair positioned at corners of mouth, extending to the posterior margin of orbit, being 7.1% (5.8–8.3%) of SL. Gill opening large; opercular membranes not connected at isthmus. Joints of dentary-angulars not close at isthmus. Ten outer rakers (1) on first gill arch. Pharyngeal teeth pattern 1,3,4–4,3,0 (1); tooth tip pointed and compressed. Vertebrae 36 (2) (Fig. 2C).

Figure 2. 

Sinocyclocheilus guiyang, IHB 202012250001, holotype, 124.0 mm SL; China: Guizhou Province: Guiyang City: Qingzhen County: Yangtze River Basin. A. Lateral view; B. Lateral, dorsal and ventral view of head; C. Micro-CT graph and reconstructed pharyngeal dentition; D. Live photo. Scale bar: 1 cm.

Dorsal fin with 3 unbranched and 8 (5) or 9 (2) branched rays, with last one divided at base; dorsal-fin length being 20.2% (17.6–24.5%) SL; origin closer to snout tip than to caudal-fin base; distal margin slightly concave, last unbranched ray strong, with serration on posterior edge; last unbranched ray split to base. Pectoral fin with 1 unbranched and 14 (6) or 15 (1) branched rays; tip extending to pelvic-fin insertion; pectoral-fin length being 21.5% (20.8–22.2%) of SL. Pelvic fin with 1 unbranched and 7 branched rays; inserted slightly posterior to dorsal-fin origin; tip not reaching to anus. Anal fin with 3 unbranched and 5 branched rays, last one divided at base; distal margin slightly concave; origin closer to pelvic-fin insertion than to caudal-fin base. Caudal fin deeply forked, with 17 (6) or 18 (1) branched rays; upper and lower lobes pointed.

Body covered with small scales, partially embedded subcutaneously; scales on lateral line slighter larger than other. Lateral line complete and horizontal, with 45 (4), 46 (2) or 47 (1) perforated scales. Scale rows above lateral line 20 (1), 21 (3), 22 (2) or 24 (1); below 13 (2) or 14 (5). Circumpeduncular scales 32 (1), 33 (1), 34 (2), 35 (2) or 36 (1).

All original morphometric measurements and meristic counts are available in Suppl. material 1.

Colouration

In freshly collected individuals (Figs 2D, 3), head and body generally pinkish, with or without pigments dorsally. A pair of dark stripes present on dorsal-posterior part of head, extending to dorsal mid-point of nape; a gold stripe extending along dorsal mid-line from nape to dorsal-fin origin. All fins transparent.

Figure 3. 

Intraspecific morphological variations of Sinocyclocheilus guiyang. A. Individual with no eyes; B. Individual with highly reduced eyes, partially covered with skin; C. Individual with dorsal pigment; D. Individual without pigment. Note that individuals of both colouration types share the presence of dark stripes on the dorsal-posterior part of the head and a gold stripe along the mid-line from the nape to the dorsal-fin origin.

In preserved specimens (Fig. 2A, B), body and head slightly yellowish, with or without pigments dorsally. Abovementioned dark stripes and gold stripe faded. All fins transparent.

Distribution and habitat

This species is presently only known from a subterranean stream flowing into the Wujiang River in the upper Yangtze River Basin in Qingzhen County, Guiyang City, Guizhou Province, China (Fig. 4). The species inhabits pools of subterranean stream with gravel substrate (Fig. 5). Video record of Sinocyclocheilus guiyang in situ is available in Suppl. material 2.

Figure 4. 

Sampling sites of Sinocyclocheilus guiyang and related species in this study.

Figure 5. 

Habitat of Sinocyclocheilus guiyang. A. The pool of a subterranean stream where S. guiyang was collected; B. S. guiyang in situ.

Etymology

The location of the subterranean stream where this new species was first collected: Guiyang City, the capital of Guizhou Province, is directly utilised as a specific epithet. The common name proposed for the new species is ‘贵阳金线鲃’ (Guiyang Golden-line Barbel).

Morphometric comparisons

Principal component analysis for Sinocyclocheilus guiyang, S. punctatus, S. multipunctatus and S. sanxiaensis, based on 29 log-transformed characters, showed that 95.23% of total variance was explained by the first three components, including 87.24% by PC1, 4.79% by PC2 and 3.20% by PC3, respectively. In the PC1 vs. PC3 scatter plot, S. guiyang and S. punctatus form a distinct cluster from the other two congeners on the PC3 axis (Fig. 6A). The characters with major loading on PC3 included maxillary barbel length, rostral barbel length, eye diameter, width between posterior nostrils and pectoral-fin base length (Table 4). Further PCA in S. guiyang and S. punctatus demonstrated that the first three components explained 97.26% of total variance, in which PC1, PC2 and PC3 explained 93.31%, 2.29% and 1.66%, respectively. Sinocyclocheilus guiyang is separated from S. punctatus on the PC2 axis in the PC1 vs. PC2 scatter plot (Fig. 6B). Eye diameter, maxillary barbel length, width between posterior nostrils, rostral barbel length and snout width are major loading characters on PC2 (Table 4). Linear regression analysis also support S. multipunctatus as distinct from S. guiyang and S. punctatus by shorter maxillary (7.2–13.3% SL vs. 5.8–8.3% in S. guiyang, 4.9–9.4% in S. punctatus) and rostral barbel lengths (6.0–10.7% SL vs. 4.9–7.1% in S. guiyang, 4.9–6.7% in S. punctatus) (Fig. 6C, D), whereas S. guiyang further differed from S. punctatus by shorter prenostril length (4.5–6.0% of SL vs. 5.8–7.6%) and higher caudal peduncle depth to caudal peduncle length ratio (0.55–0.67 vs. 0.45–0.56) (Fig. 6E, F).

Figure 6. 

A. Scatter plot of 1st and 3rd principal components for Sinocyclocheilus guiyang, S. punctatus, S. multipunctatus and S. sanxiaensis; B. Scatter plot of 1st and 2nd principal components for S. guiyang and S. punctatus; relationships between C. Rostral barbel length and head length, D. Maxillary barbel length and head length for S. guiyang, S. punctatus and S. multipunctatus; relationships between E. Prenostril length and head length, F. Caudal peduncle depth and caudal peduncle length for S. guiyang and S. punctatus.

Table 4.
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PCA loadings of the first three principal components extracted from 29 morphometric data for Sinocyclocheilus guiyang and related species.

S. guiyang, S. punctatus, S. multipunctatus, S. sanxiaensis S. guiyang, S. punctatus
PC1 PC2 PC3 PC1 PC2 PC3
Standard length 0.991 -0.062 0.028 0.995 0.026 -0.045
Body depth 0.948 -0.034 -0.165 0.966 -0.049 -0.204
Predorsal length 0.991 -0.035 -0.022 0.996 0.008 0.050
Dorsal-fin base length 0.978 -0.090 0.030 0.989 -0.011 -0.027
Dorsal-fin length 0.928 0.027 0.019 0.895 -0.115 0.376
Pre-anal length 0.986 -0.058 0.037 0.995 0.020 -0.015
Anal-fin base length 0.967 -0.107 -0.041 0.974 0.020 -0.104
Anal-fin length 0.962 -0.032 -0.075 0.985 0.073 0.101
Prepectoral length 0.990 -0.029 -0.071 0.992 -0.024 0.074
Pectoral-fin base length 0.712 0.655 0.193 0.963 0.161 -0.080
Pectoral-fin length 0.978 -0.011 -0.043 0.970 -0.092 0.132
Prepelvic length 0.991 -0.040 0.020 0.996 -0.005 -0.008
Pelvic-fin base length 0.732 0.636 0.097 0.954 -0.019 -0.228
Pelvic-fin length 0.976 0.002 -0.134 0.987 0.097 0.056
Caudal peduncle length 0.954 -0.074 0.049 0.958 0.092 -0.170
Caudal peduncle depth 0.957 -0.019 -0.065 0.956 -0.107 -0.230
Head length 0.990 -0.035 -0.072 0.997 0.008 0.034
Head depth 0.991 -0.053 -0.046 0.996 -0.014 0.000
Head width 0.972 -0.080 0.048 0.970 -0.104 0.006
Snout length 0.966 0.183 -0.094 0.983 -0.056 0.029
Eye diameter 0.716 0.389 0.408 0.758 0.632 0.056
Interorbital width 0.982 0.010 -0.086 0.979 -0.147 -0.107
Prenostril length 0.961 0.052 -0.036 0.954 0.150 0.045
Width between posterior nostrils 0.956 0.009 -0.199 0.959 -0.183 -0.170
Upper jaw length 0.962 -0.116 -0.179 0.983 -0.040 0.108
Lower jaw length 0.964 -0.118 -0.156 0.986 -0.008 0.103
Mouth width 0.958 0.031 -0.052 0.954 0.155 -0.003
Rostral barbel length 0.731 -0.440 0.492 0.956 -0.161 0.081
Maxillary barbel length 0.764 -0.300 0.524 0.938 -0.185 0.169

Molecular data analyses

A total of 1134 bps were included in the aligned dataset of cytb gene, with 661 conservative sites, 473 variable sites, 390 parsimony informative sites and 83 singleton sites. The mean frequency of four nucleotides in the sequences of Sinocyclocheilus guiyang is A = 29.7%, G = 14.2%, C = 26.2% and T = 29.9%. The phylogenetic trees, reconstructed by ML and BI methods, are identical in topology (Fig. 7). The monophyletic linage of Sinocyclocheilus guiyang is robustly supported by 100% posterior probabilities and 99% bootstrap supports and is sister to S. punctatus. The lineage of the two species clustered with the lineage comprising sequences of S. multipunctatus, S. cyphotergous and S. sanxiaensis. Additionally, the topology of phylogenetic reconstruction in the present study supports the monophyly of the S. cyphotergous – S. multipunctatus species group. Average genetic distances derived from cytb sequences of Sinocyclocheilus species distributed in Guizhou Province or the Yangtze River Basin are given in Table 5. The intraspecific distance of S. guiyang is 0.1% and the mean distances between the new species and other congeners range from 2.3% (vs. S. punctatus) to 13.8% (vs. S. wumengshanensis).

Figure 7. 

Phylogenetic tree of Sinocyclocheilus species inferred from cytb using Bayesian Inference and Maximum Likelihood methods. Node values show posterior probabilities/bootstrap supports if greater than 50%. Currently known distribution of species of the S. cyphotergous – S. multipunctatus group are shown on map.

Table 5.
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Average uncorrected pairwise genetic distance (p-distance, %) derived from cytb in 15 species of Sinocyclocheilus distributed in Guizhou Province or the Yangtze River Basin. Bold numbers, intraspecific distances; regular numbers, interspecific distances; n/a, not available.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
1. S. guiyang 0.1
2. S. multipunctatus 2.5 0.4
3. S. punctatus 2.3 2.6 0.7
4. S. cyphotergous 2.8 1.1 3.1 0.8
5. S. sanxiaensis 3.2 1.0 2.9 1.6 n/a
6. S. longibarbus 10.9 11.0 11.2 11.2 11.6 n/a
7. S. grahami 11.7 11.6 11.8 11.9 12.2 11.5 n/a
8. S. wumengshanensis 12.3 11.8 12.1 12.1 12.3 11.7 4.2 n/a
9. S. angustiporus 11.4 11.1 11.5 11.3 11.6 10.4 7.7 7.1 n/a
10. S. macrolepis 11.5 11.4 11.9 11.7 12.0 11.1 12.7 12.6 11.5 n/a
11. S. bicornutus 10.8 10.9 11.4 11.1 11.4 10.3 12.2 12.4 11.1 11.3 n/a
12. S. zhenfengensis 10.9 10.8 11.2 10.9 11.3 10.0 12.0 12.4 11.3 11.2 2.9 n/a
13. S. angularis 11.2 11.2 11.1 11.5 11.6 9.6 11.8 12.3 11.2 11.6 2.8 2.4 n/a
14. S. longicornus 11.9 11.9 11.8 11.9 12.4 10.8 12.3 12.5 11.3 11.8 5.8 6.5 5.9 n/a
15. S. xingyiensis 11.1 11.1 11.5 11.3 11.5 10.1 12.6 12.8 11.3 12.0 2.3 2.9 1.9 6.3 n/a

Discussion

The new species is the first described troglobiotic species of genus Sinocyclocheilus in the Wujiang River of upper Yangtze River Basin in Guizhou Province. Three characters are useful for distinguishing Sinocyclocheilus guiyang from all other Sinocyclocheilus species, except S. jinxiensis and S. sanxiaensis (Fig. 8): short maxillary barbel not reaching posterior edge of preoperculum, absence of horn-like structure and degenerated (lost or highly reduced) eye. It is distinct from S. jinxiensis and S. sanxiaensis in having shorter (vs. longer) pectoral fins, just reaching (vs. significantly extending beyond) the base of pelvic fin. It further differs from S. jinxiensis in possessing degenerated body scales (20–24 scale rows above lateral line vs. 8–9), and from S. sanxiaensis in having shorter (vs. longer) snout (length 9.9–11.0% of SL vs. 16.4%) and longer (vs. shorter) maxillary barbel, reaching to posterior edge of orbit, length 5.8–8.3% of SL (vs. not reaching to anterior edge of orbit, 4.2%).

Figure 8. 

Lateral view of A. Sinocyclocheilus multipunctatus, IHB 202302080001, 110.3 mm SL; China: Yangtze River Basin; B. S. punctatus, ZJFR 2311004, 110.1 mm SL; China: Pearl River Basin; C. S. guiyang, IHB 202012250001, holotype, 124.0 mm SL; China: Yangtze River Basin; D. S. sanxiaensis, KIZ 2019000001, holotype, 164.1 mm SL; China: Yangtze River Basin; E. S. cyphotergous, IHB 202207280011, 71.3 mm SL; China: Pearl River Basin; F. S. jinxiensis, GXU 23070020, 85.8mm SL; China: Pearl River Basin. Scale bar: 1 cm.

Although Sinocyclocheilus guiyang displays a high degree of eye degeneration, there is intraspecific variations in the eyes, ranging from absence of eye to highly reduced eyes partially covered by skin (Fig. 3A, B). Similar variations have been recorded in observations of its congeners. The eyes of S. cyphotergous have been described as ‘very small’ in its re-description (Huang et al. 2017) and it is the same case with some of our newly-collected specimens (Fig. 8E); however, some specimens are presented as eyeless (See Suppl. material 3). Sinocyclocheilus bicornutus Wang & Liao, 1997, a cave-dwelling species, also demonstrated polymorphism in eye mode (Wen et al. 2023). Variations in such regressive characters in troglobitic fishes are common, indicating that eye degeneration might not be a totally reliable character in morphology species delineation of Sinocyclocheilus. Accordingly, it is of vital importance to also compare the morphology of this new species with other congeneric species possessing a short maxillary barbel, no horn-like structure and normal eyes, including S. jiuxuensis Li & Lan, 2003, S. brevibarbatus Zhao, Lan & Zhang, 2009, S. mashanensis Wu, Liao & Li, 2010, S. yangzongensis Chu & Chen, 1977, S. multipunctatus and S. punctatus. Amongst these species, S. multipunctatus and S. punctatus showed close phylogenetic relationships with S. guiyang, which all belong to the S. cyphotergous – S. multipunctatus group. Sinocyclocheilus guiyang can be further differentiated from S. jiuxuensis, S. brevibarbatus and S. mashanensis by the following characters: pectoral fin just reaching pelvic fin insertion (vs. pectoral fin highly developed, significantly reaching beyond pelvic fin insertion), pelvic-fin origin posterior to dorsal-fin origin (vs. anterior to dorsal-fin origin) (Zhao and Zhang 2009). In addition, S. guiyang further differs from S. yangzongensis in having a deeper body (depth 26.7–33.1% SL vs. 21.3–28.5%), longer dorsal fin base (length 15.3–16.8% SL vs. 8.0–12.6%) and less lateral line scales (45–47 vs. 71–79) (Zhao and Zhang 2009).

Sinocyclocheilus guiyang is undoubtedly a member of the S. cyphotergous – S. multipunctatus species group, as evidenced by both morphology and phylogenetic results in this study. The monophyly of the S. cyphotergous – S. multipunctatus group has also been confirmed in previous works (Wen et al. 2022; Jiang et al. 2023; Xu et al. 2023). Excluding S. sanxiaensis, which has been mentioned above, S. guiyang differs from S. cyphotergous by the absence of a humpback, from S. multipunctatus in having developed pectoral fins extending (vs. not extending) to pelvic-fin insertion and fewer lateral line scales (45–47 vs. 53–60), from S. punctatus in having longer maxillary barbels reaching to posterior edge of orbit (vs. reaching to anterior edge of orbit). The principal component analysis of measurement characters also confirms the morphological distinctness of S. guiyang from other members of the S. cyphotergous – S. multipunctatus group lacking horn-like structures (Fig. 6A).

As sister to one another, the pairwise distance between Sinocyclocheilus guiyang and S. punctatus is 2.3%, exceeding the 2% mitochondrial DNA threshold which is often indicative of valid species in most groups (Avies and Walker 1999) and coincides with distances used for currently described species in Sinocyclocheilus. The genetic distances between sibling species being comparatively low might be a trait common across the genus Sinocyclocheilus, which has undergone recent divergence in extreme subterranean environments (Mao et al. 2022). In addition, S. guiyang and S. punctatus display allopatric distribution patterns as S. punctatus is confined in the Longjiang River (a tributary of Liujiang River in the Pearl River Basin), while S. guiyang only occurs in Wujiang River that belongs to the upper Yangtze River Basin. The species validity of S. guiyang can be confirmed under an integrative framework combining numerous lines of evidence, comprised of morphological distinctness, molecular phylogeny and geographical range. Moreover, samples of S. multipunctatus formed a paraphyletic entity in the phylogenetic tree. It is evident that geographic divergence has occurred as the Yangtze River population showed close affinities to S. sanxiaensis, while the Pearl River population is located at the base of the paraphyly (Fig. 7), implying the existence of cryptic species diversity within S. multipunctatus that warrants taxonomic revision in the future.

The fish diversity in the Yangtze River Basin of Guiyang City, the most urbanised area of Guizhou, has long been underestimated (Zeng and Liu 2020). The increasing discoveries of narrowly distributed species in this area have raised concerns for the conservation of these species (Liu et al. 2022; Zeng et al. 2022). Human disturbance to the habitat and climate change have exacerbated the risk of extinction of cave species (Shu et al. 2013; Mouser et al. 2022). Recent years have witnessed a dramatic increase in land use, fishing pressure, cave tourism and invasion of a large amount of Procambarus clarkii Girard, 1852 in the type locality of Sinocyclocheilus guiyang (See Suppl. material 4), as well as frequent onset of droughts. Moreover, the estimated population size of the new species is extremely small, as only 25 individuals in total were recorded during our surveys and has suffered a population decline in the recent 2 years (Table 6). S. guiyang will be automatically assigned to the list of 2nd Class of the national protected animals after its description as the whole Sinocyclocheilus species are within this list since 2021. Construction of a small conservation area with limited human disturbance in the existing habitats of this new species under extreme threat should be considered in priority.

Table 6.
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Number of individuals of Sinocyclocheilus guiyang in type locality recorded each year during the survey.

Year 2019 2020 2021 2022 2023 2024
Number 5 7 5 6 1 1

Material examined

Sinocyclocheilus cyphotergous: IHB 202207280006–12, 7 specimens, 54.2–82.0 mm SL; a tiankeng of the Mengjiang River System in the Pearl River Basin at Pingtang County, Qiannan Prefecture, Guizhou Province, China. IHB 202302080002–03, 2 specimens, 71.5–84.6 mm SL; a subterranean tributary of the Mengjiang River System in the Pearl River Basin at Luodian County, Qiannan Prefecture, Guizhou Province, China.

Sinocyclocheilus multipunctatus: IHB 2014040001, 1 specimen, 96.4 mm SL; a vauclusian spring of the Mengjiang River System in the Pearl River Basin at Huaxi District, Guiyang City, Guizhou Province, China. IHB 2019070001, IHB 202302080001, 2 specimens, 87.6–110.3 mm SL; a vauclusian spring of the Wujiang River System in the Yangtze River Basin at Wudang District, Guiyang City, Guizhou Province, China. IHB 202307067001–02, 2 specimens, 83.6–88.0 mm SL; Bawang River of the Mengjiang River System in the Pearl River Basin at Huishui County, Qiannan Prefecture, Guizhou Province, China. ZJFR 2306003–05, ZJFR 2312003, 4 specimens, 110.3–137.7 mm SL; a vauclusian spring of the Wujiang River System in the Yangtze River Basin at Xixiu District, Anshun City, Guizhou Province, China.

Sinocyclocheilus punctatus: IHB 20210697587, IHB 202311064952, ZJFR 2311004, 3 specimens, 109.4–152.3 mm SL; a subterranean tributary of the Liujiang River System in the Pearl River Basin at Libo County, Qiannan Prefecture, Guizhou Province, China. IHB 20222936A–38A, ZJFR 202311001, ZJFR 202312002, 5, 129.4–226.0 mm SL; a subterranean tributary of the Liujiang River System in the Pearl River Basin at Huanjiang County, Hechi City, Guangxi Province, China.

Sinocyclocheilus sanxiaensis: KIZ 2019000001, holotype, 164.1 mm SL; near the north bank of the Three Gorges Reservoir in the mainstream of Yangtze River at Zigui County, Yichang City, Hubei Province, China.

Sinocyclocheilus jinxiensis: GXU 23070020, 1 specimen, 85.8mm SL; a vauclusian spring of the Yujiang River System in the Pearl River Basin at Jingxi County, Baise City, Guangxi Province, China.

Conflict of interest

The authors declare that they have no conflict of interest.

Funding

This work was partially funded by a grant from the Ecological Monitoring and Restoration in Dongfeng Lake and Liuchong River Basin (No: 2023-1).

Authors’ contributions

Zhi-Xuan Zeng and Jia-Jun Zhou designed the study and revised the manuscript. Guang-Yuan Cheng launched the surveys. Xiao-Long Lu extracted the genomic DNA and performed the molecular analysis. Wei-Han Shao examined the specimens and prepared the manuscript. All authors read and approved the final version of the manuscript.

Acknowledgements

We are grateful to Rui Min (Kunming Natural History Museum of Zoology, KIZ) and Ye-Wei Liu, Cheng-Hai Fu (College of Forestry, Guangxi University) for providing comparative specimens; to Ji-Yong Wang (Guiyang Qianren Ecological Conservation Center) for assistance in the field survey; and to Zheng-Meng Yang for drawing of the new species.

References

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Supplementary materials

Supplementary material 1 

Measurements of the type specimens of Sinocyclocheilus guiyang

Wei-Han Shao, Guang-Yuan Cheng, Xiao-Long Lu, Jia-Jun Zhou, Zhi-Xuan Zeng

Data type: xlsx

This dataset is made available under the Open Database License (http://opendatacommons.org/licenses/odbl/1.0/). The Open Database License (ODbL) is a license agreement intended to allow users to freely share, modify, and use this Dataset while maintaining this same freedom for others, provided that the original source and author(s) are credited.
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Supplementary material 2 

Video of Sinocyclocheilus guiyang in situ

Wei-Han Shao, Guang-Yuan Cheng, Xiao-Long Lu, Jia-Jun Zhou, Zhi-Xuan Zeng

Data type: mp4

This dataset is made available under the Open Database License (http://opendatacommons.org/licenses/odbl/1.0/). The Open Database License (ODbL) is a license agreement intended to allow users to freely share, modify, and use this Dataset while maintaining this same freedom for others, provided that the original source and author(s) are credited.
Download file (18.99 MB)
Supplementary material 3 

Eyeless specimen of Sinocyclocheilus cyphotergous

Wei-Han Shao, Guang-Yuan Cheng, Xiao-Long Lu, Jia-Jun Zhou, Zhi-Xuan Zeng

Data type: tif

Explanation note: IHB 202207280010, 82.0 mm SL; China: Qiannan Prefecture: Pingtang County: Pearl River Basin.

This dataset is made available under the Open Database License (http://opendatacommons.org/licenses/odbl/1.0/). The Open Database License (ODbL) is a license agreement intended to allow users to freely share, modify, and use this Dataset while maintaining this same freedom for others, provided that the original source and author(s) are credited.
Download file (4.80 MB)
Supplementary material 4 

Human disturbance and alien species invasion to the type locality of Sinocyclocheilus guiyang

Wei-Han Shao, Guang-Yuan Cheng, Xiao-Long Lu, Jia-Jun Zhou, Zhi-Xuan Zeng

Data type: tif

This dataset is made available under the Open Database License (http://opendatacommons.org/licenses/odbl/1.0/). The Open Database License (ODbL) is a license agreement intended to allow users to freely share, modify, and use this Dataset while maintaining this same freedom for others, provided that the original source and author(s) are credited.
Download file (9.36 MB)
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