Sinocyclocheilus guiyang, Shao & Cheng & Lu & Zhou & Zeng, 2024

Shao, Wei-Han, Cheng, Guang-Yuan, Lu, Xiao-Long, Zhou, Jia-Jun & Zeng, Zhi-Xuan, 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), pp. 515-529 : 515-529

Sinocyclocheilus guiyang sp. nov.

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.

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. 2 C ).

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 2 D , 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.

In preserved specimens (Fig. 2 A, 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.

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 PC 1, 4.79 % by PC 2 and 3.20 % by PC 3, respectively. In the PC 1 vs. PC 3 scatter plot, S. guiyang and S. punctatus form a distinct cluster from the other two congeners on the PC 3 axis (Fig. 6 A ). The characters with major loading on PC 3 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 PC 1, PC 2 and PC 3 explained 93.31 %, 2.29 % and 1.66 %, respectively. Sinocyclocheilus guiyang is separated from S. punctatus on the PC 2 axis in the PC 1 vs. PC 2 scatter plot (Fig. 6 B ). Eye diameter, maxillary barbel length, width between posterior nostrils, rostral barbel length and snout width are major loading characters on PC 2 (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. 6 C, 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. 6 E, F ).

Molecular data analyses.

A total of 1134 bps were included in the aligned dataset of cyt b 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 cyt b 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 ).

Figures

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.

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.

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.

Figure 6. A. Scatter plot of 1 st and 3 rd principal components for Sinocyclocheilus guiyang, S. punctatus, S. multipunctatus and S. sanxiaensis; B. Scatter plot of 1 st and 2 nd 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.

Figure 7. Phylogenetic tree of Sinocyclocheilus species inferred from cyt b 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.