Zoosyst. Evol. 100 (2) 2024, 583-595 | DOI 10.3897/zse.100.120676 yee BERLIN Tachysurus wuyueensis (Teleostei, Bagridae), a new species of catfish from the Qiantang-Jiang basin, southeast China Jia-Jun Zhou', Le-Yang Yuan*, Wei-Han Shao? 1 Zhejiang Forest Resource Monitoring Center, Hangzhou, China 2 Zhejiang Museum of National History, Hangzhou, China 3 Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, China https://zoobank. org/3 DIOFE75-FC05-4A93-A03A-17C77BD60999 Corresponding author: Wei-Han Shao (shaoweihanl1008@163.com) Academic editor: Nicolas Hubert # Received 10 February 2024 Accepted 28 March 2024 Published 17 May 2024 Abstract Tachysurus wuyueensis, new species, is described from the Qiantang-Jiang Basin, situated in Suichang County, Zhejiang Province and Xiuning County, Anhui Province, southeast China. The coastal basin drains into the East China Sea. The new species belongs to the T. pratti-T: truncatus group within the genus 7achysurus defined by having a smooth anterior margin of the pectoral-fin spine, short max- illary barbels not extending beyond the base of the pectoral-fin spine, short dorsal spine not exceeding two thirds of head length and an emarginated caudal fin. This new species is distinct from all other species of this group, 7achysurus pratti (Gunther, 1892), 7: truncatus (Regan 1913), 7 gracilis (Li, Chen & Chan, 2005) and 7. brachyrhabdion (Cheng, Ishihara & Zhang, 2008), in having a shorter prepelvic body (length 40.0-46.4% of SL vs. 45.8-54.8%). It further differs from 7’ pratti, T. truncatus and T: gracilis in having more vertebrae (45-47 vs. 37-44) and more anal fin rays (21—25 vs. 14-20), from 7° brachyrhabdion in having a more slender body (depth 10.1—13.5% of HL vs. 13.1-17.6%). Molecular phylogeny, based on the mitochondrial cytochrome b (cyt. 6) gene confirms the validity of 77 wuyueensis and the 7? pratti-T. truncatus group. Furthermore, this study addresses the diagnostic traits distinguishing the 7° pratti-T. truncatus group from the 7! tenuis-T. crassilabris group which have historically been treated as a single species group due to morphological similarities. Key Words Caudal fin shape, new taxon, stream-dewelling species, taxonomy Introduction The genus Jachysurus Lacépeéde 1803 is a group of East Asian endemic catfish that 1s widely distributed throughout most of the East Asian continent (Ku et al. 2007; Watanabe 2010; Shao and Zhang 2023). It is also one of the most diversified catfish genus in China con- taining more than thirty species with strong differenti- ation in ecological niches (Shao et al. 2021; Shao and Zhang 2023). South China, which is characterised by high mountains, deep valleys and abundant precipita- tion (Lopez-Pujol et al. 2011; Wang et al. 2018; Sun et al. 2021), harbours numerous Jachysurus species re- stricted to montane streams with fast-flowing high-ox- ygen waters and predominance of rocky substrate, for example, Zachysurus ondon (Shaw 1930), T: adiposa- lis (Oshima 1919), T. albomarginatus (Rendahl 1928), T. trilineatus (Zheng 1979) and T- tenuis (Gunther 1873). Unlike its congeners, species of Zachysurus always pos- sess elongated bodies and rounded, truncated or slightly emarginated (round-tailed) caudal fins regarded herein as key adaptions for the torrent environments (Gosline 1997; Krishnadas et al. 2018). Moreover, the absence of diagnosable characters and ambiguous descriptions have obscured the species boundaries of these species (Ferraris 2007; Shao et al. 2021). For instance, T. albo- marginatus has long been synonymised under 7! tenuis (Zheng & Dai, 1999) until Cheng et al. (2021) resur- rected the former species, based on morphometric and osteological analyses. Copyright Jia-Jun, Z. et al. 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. 584 Jia-Jun, Z. et al.: A new Tachysurus species from the Qiantang-Jiang basin, China In addition, rheophilic (fast-water) fishes are always confined to a narrow distribution which limits their dis- persal ability and contributes to their habitat fragmen- tation (Lima et al. 2017). Previous works have high- lighted the underestimated diversity of Tachysurus, v.gr., T; albomarginatus that may be an assemblage of five species (Cheng et al. 2021; Shao et al. 2021). A similar scenario occurs in 7. adiposalis, originally de- scribed by Oshima (1919) on a single specimen of 170 mm SL (standard length) collected from the Tamusui River in Taiwan. 7: adiposalis has been treated as wide- spread species, with a distribution including Tatwan and river basins from the southern region of Chinese mainland, such as the mid-lower Yangtze, Pearl Riv- er and Qiantang River (= Qiantang-Jiang in Chinese) (Zheng and Dai 1999). The key characters useful in dif- ferentiating Zachysurus species are absent or obscured in the original description of 7. adiposalis, which re- sulted in the taxonomic confusion. Recent studies have suggested that specimens from the Xi-Jiang (the Pearl River Basin) and the Yuan-Jiang (the middle Yangtze River Basin) belonging to 7 adiposalis s.1. were de- termined as Jachysurus gracilis (Li, Chen & Chan, 2005) and Tachysurus brachyrhabdion (Cheng, Ishi- hara & Zhang, 2008). However, the taxonomic status of specimens from the Qiantang-Jiang which were also recognised as Zachysurus adiposalis has not been men- tioned in previous studies and it potentially represents an undescribed species. A fish field survey conducted by the authors 1n the Qiantang-Jiang Basin of Zhejiang and Anhui Provinces yielded 14 specimens initially identified as T. adiposis. Careful morphological examination revealed that these were, in fact, not conspecific with any other known spe- cies of Zachysurus and represent a new species. The purpose of the present paper is to provide a formal de- scription of this unnamed species, based on multiple lines of evidence containing morphological and phylo- genetic datasets. Materials and methods Fourteen specimens of the new species were caught during two field surveys conducted, respectively, in September 2020 and May 2023 into the Qiantang-Ji- ang flowing into the East China Sea. Amongst them, six specimens were fixed in 10% formalin after removal of right-side pelvic-fin clips. These fin clips were stored in 95% ethyl alcohol and utilised for molecular analy- sis. The remaining caught specimens were directly pre- served in 10% formalin preservative for morphological examination. Their voucher specimens are deposited in the Museum of Aquatic Organisms of the Institute of Hydrobiology (IHB), Chinese Academy of Sciences, Wuhan. Eight species, including 7 gracilis, T. trun- catus, T. pratti, T- brachyrhabdion, T. crassilabris, zse.pensoft.net T. albomarginatus, T: adiposalis and T. tenuis, were morphologically examined in this study, which came from the following collections: Museum of Aquatic Or- ganisms of Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan (IHB), the Natural History Muse- um, London (BMNH) and French Museum of Natural History, Paris (FMNH). Measurements were taken point to point with digital calipers linked to a data recording computer and data were recorded to the nearest 0.1 mm and made on the left side of each individual whenever possible, following the methods for Cheng et al. (2008). The head length and measurements of other parts of the body are estimated as percentages of the standard length (SL). Subunits of head are provided as percentages of the head length (HL). The number of rays from the dorsal- and anal fins were count- ed using the method by Watanabe (1995). Other fin rays were counted under a binocular dissecting microscope utilising transmitted light. Vertebral count was taken from X-ray photographs, with the anterior five vertebrae, namely the Weberian complex, not counted. Morphometric measurements were subject to principal component analysis (PCA) in order to examine external morphological differentiation and determine the relative contributions of specific variables to morphological dif- ferences in the target species. PCA was run with SPSS 16 (SPSS, Chicago, IL, USA). Prior to the analysis, all morphometric measurements, except standard length, were normalised following the method of Reist (1985) to eliminate the influence of allometry of body parts and sample size. Phylogenetic analysis was performed on cyt. b and the sequences uploaded to NCBI GenBank (Table 1). The thirty-eight cyt. b gene sequences, here amplified from twenty-five species of Zachysurus, were used for molecular phylogenetic analysis. Zachysurus trilineatus was used as the outgroup which is the basal lineage of Tachysurus genus (Ku et al. 2007). The sequences were revised manually and then aligned using ClustalW in MEGA7 (Kumar et al. 2016). Both Maximum Likeli- hood (ML) and Bayesian Inference (BI) methods were utilised to reconstruct the phylogenetic relationships. The optimal nucleotide substitution model was selected by ModelFinder (Kalyaanamoorthy et al. 2017) according to the Akaike Information Criterion. Maximum Likelihood analysis was run by IQ-tree (Nguyen et al. 2015), with the selected TIM3+F+I+G4 model and 1,000 non-para- metric bootstrap replicates. Bayesian Inference was per- formed in MrBayes (Ronquist et al. 2012) under the se- lected GITR+F+I+G4 model. Two independent runs were carried out with four Monte Carlo Markov chains (three hot chains and one cold chain) for 20 million generations to calculate posterior probability. Trees were sampled ev- ery 1000 generations. The initial 25% of sampled trees were discarded as burn-in. Convergence of the runs was assessed by the average standard deviation of split fre- quencies (< 0.01). Zoosyst. Evol. 100 (2) 2024, 583-595 Table 1. GenBank accession numbers for molecular phylogenetic analysis. 585 Taxon Locality Ingroup (1) Tachysurus albomarginatus Zhejiang, China (2) Tachysurus analis Jiangxi, China (3) Tachysurus argentivittatus Jiangxi, China (4) Tachysurus brachyrhabdion 1 Guizhou, China Tachysurus brachyrhabdion 2 Guizhou, China Tachysurus brachyrhabdion 3 Hunan, China (5) Tachysurus crassilabris Hunan, China (6) Tachysurus dumerili Jiangsu, China (7) Tachysurus gracilis] Guangxi, China (8) Tachysurus gracilis 2 Hunan, China (9) Tachysurus intermedius Hainan, China (10) Tachysurus kyphus Guangxi,China (11) Tachysurus lani Guangxi, China (12) Tachysurus longispinalis Vietnam (13) Tachysurus nitidus Hunan, China (14) Tachysurus ondon Zhejiang, China (15) Tachysurus pratti 1 Sichuan, China Tachysurus pratti 2 Yunan, China (16) Tachysurus similis Fujian, China (17) Tachysurus sinensis Hubei, China (18) Tachysurus tenuis Zhejiang, China (19) Tachysurus truncatus 1 Sichuan, China Tachysurus truncatus 2 Shaanxi, China (20) Tachysurus ussuriensis Heilongjiang, China (21) — Tachysurus vachelli Hubei, China (22) Tachysurus virgatus Hainan, China (23) Tachysurus wuyueensis (SUIC55690) Zhejiang, China Tachysurus wuyueensis (SUIC55691) Tachysurus wuyueensis (SUIC55692) Tachysurus wuyueensis (XIUN65294) Anhui, China Tachysurus wuyueensis (XIUN65295) Tachysurus wuyueensis (XIUN65296) (24) — Tachysurus zhangfei Hunan, China Outgroup (25) — Tachysurus trilineatus Guangdong, China The genetic distances, based on cyt. B, were computed in MEGA 7 using the Kimura-2-parameter (K2P) model (Kimura 1980). Results Phylogenetic analysis A total of 1092 bps were included in the aligned dataset of the cyt. b gene, with 668 conservative sites, 492 variable sites, 375 Parsim-informative sites and 117 singleton sites. The mean frequency of the four nucleotides in the sequenc- es of Zachysurus wuyueensis are A = 29.1%, G = 15.6%, C = 27.7% and T = 28.5%. The phylogenetic trees recon- structed by ML and BI methods are identical in topology (Fig. 1). A monophyly formed by samples of Zachysurus wuyueensis was recovered with 100% posterior probabili- ties (pp) and 1.00 bs in ML and BI trees, respectively and be- longed to a clade containing 7° gracilis, T? brachyrhabdion, T. truncatus and T: pratti. Tachysurus wuyueensis 1s sister to a species pair consisting of 7° gracilis and T. brachyrhabdion Distribution Accession number Qiantang-Jiang PP266663 Gan-Jiang of lower Yangtze River PP266668 Gan-Jiang of lower Yangtze River PP266678 Yuan-Jiang of middle Yangtze River PP266650 PP266651 PP266652 Xiang-Jiang of middle Yangtze River PP266665 Lower Yangtze River PP266661 Xiang-Jiang of middle Yangtze River PP266654 Lijiang River of Pearl River PP266655 Nandu-Jiang PP266676 Fangcheng- Jiang PP266671 GuiJiang of the Pearl River PP266662 Red River PP266672 Xiang-Jiang of middle Yangtze River PP266660 Ou-Jiang PP266677 Jinsha-Jiang of upper Yangtze River PP266656 PP266657 Min-Jiang PP266664 Middle Yangtze River PP266674 PP266666 Upper Yangtze River PP266658 Han-Jiang of middle Yangtze River PP266659 Heilong-Jiang PP266669 Middle Yangtze River PP266670 Jiajihe River PP266673 Qiantang-Jiang PP266644 PP266645 PP266646 PP266647 PP266648 PP266649 Yuan-Jiang of middle Yangtze River PP266667 Dong-Jiang of Pearl River PP266679 and the above all are sister to another species pair: 7° trun- catus and T: pratti. Herein, these five species are designated as belonging to the 7’ truncatus-T. pratti group given their affinities in both morphology and molecular phylogeny. The estimated K2P genetic distances of the cyt. b gene between 7 wuyueensis and congenerics range from 6.9% to 12.6% (Table 2). The distances between 7’ wuyueensis and members of the 7: pratti-T! truncatus group are in a range of 6.9-8.3%. The paired species, 7 truncatus and T. pratti, endemic to the upper Yangtze River Basin have a 1.4% ge- netic distance, while another paired species, 7’ brachyrhab- dion and T: gracilis, displays a 4.1% distance. The range of intraspecific genetic distances within 7’ wuyueensis is 0.1%. Table 2. K2P distances (%) for species within the Zachysurus pratti-Tachysurus truncatus group, based on the cyt. b gene. 1 2 3 4 1. T. wuyueensis sp. nov. 2. T. pratti 7.1 3. T. truncatus 6.9 1.4 4. T. gracilis 8.3 9.1 8.6 5. T. brachydhrbdion LD 8.3 8.0 4.1 zse.pensoft.net 586 Jia-Jun, Z. et al.: A new Tachysurus species from the Qiantang-Jiang basin, China 88/1 71/0.86 74 /* 100/1 100/0. 81 88/0.99 99/1 76/0.81 — 72/0.83 91/0.88 100/1 94/ * 77/0.98 100/0.89 100/1 T. trilineatus 0.03 SUIC55690 XIUNING65296 SUIC55692 T. wuyueensis species nova XIUNING65295 100/1 XIUNING65294 SUIC55691 T. brachyrhabdion 1 T. brachyrhabdion 2 96/* 27 T. pratti-T. truncatus 100/1 T. brachyrhabdion 3 group 4100/1 4 7- gracilis 1 T. gracilis 2 T. pratti 7 100/1 T. pratti 2 T. truncatus 1 100/1 T. truncatus 2 T.nitidus__—_—_—_| T. nitidus group 72/* T. dumerili pies T. lani hy T. albomarginatus +) T. similis “je T. crassilabris T. tenuis - T. crassilabris group T. tenuis 109/0.88L 7. zhangfei T. analis T. ussuriensis T. vachelli | T. vachelli group T. kyphus T. longispinalis T. virgatus T. sinensis T. eupogon T. intermedius T. ondon T. argentivittatus Figure 1. Phylogenetic tree of Zachysurus species inferred from cyt. b using Bayesian Inference and Maximum Likelihood methods. Bayesian posterior probabilities (> 0.8) and Maximum Likelihood bootstrap values (> 70%) are shown, respectively. Principal component analysis The 7: truncatus-T. pratti group can be differentiated from all other Zachysurus species by having a smooth anterior margin of the pectoral spine, short dorsal spine not ex- ceeding two-thirds of head length and short maxillary bar- bels not extending beyond the base of the pectoral spine. Amongst these five species, excluding 7. pratti which has a deeply forked caudal fin (Fig. 2), the other four round- tailed species were included in the principal component analysis performed on the variance-covariance matrix of log-transformed measurements (Table 3; Fig. 3). The re- sults show that the combination of PC1 against PC3 and PC2 against PC3 enabled the separation of 77 wuyueen- sis from 7: truncatus, T: gracilis and T. brachyrhabdion. Characters with main loadings in PC1 were the adipose to caudal distance and body depth at anus; in PC2, they were the outer mandibular barbel length, anal-fin base length, nasal-barbel length and maxillary barbel length; and, in PC3, they were the inner mandibular barbel length, eye diameter and interorbital width (Table 3). Morphological comparisons Amongst the characters displaying main loading in PCA, some exhibit stable variations between species and can zse.pensoft.net Table 3. Loadings on the first three principal components ex- tracted from morphometric data for 7) wuyueensis, T: truncatus, T. brachyrhabdion and T. gracilis. PCl PC2 PC3 Standard length 2A? 18.5 78 Body depth at anus 21.3 5.6 26.4 Predorsal length 19.4 7.0 6.7 Pre-anal length 21.1 9.6 9.1 Prepelvic length 20.7 9.3 7.5 Prepectoral length 18.0 3.6 14.0 Length of dorsalfin spine 15.8 14.2 8.5 Length of dorsalfin base 20.3 Di? 6.8 Length of pectoral-fin spine 16.1 17-2 Leif Length of analfin base 19.6 41.2 29.2 Height of adipose fin 16.5 13.7 20.2 Adipose to caudal distance 23.9 19.1 13.8 Length of caudal peduncle 24.7 21.9 24.2 Depth of caudal peduncle 19.7 4.2 23.5 Head length at latera 19.0 1.2 5.5 Head depth 18.3 0.08 122 Head width 19.8 3.0 18.0 Snout length 18.5 0.9 14.7 Interorbital width 20.2 8.8 30.2 Eye diameter 12.9 22.6 36.2 Mouth width 20.4 7.7 1boay Length of nasal barbel 21.8 37.6 23.4 Length of maxillary barbel 22.6 36.3 3.8 Length of inner mandibular barbel 21.4 24.7 45.9 Length of outer mandibular barbel 277, 46.2 19.5 Zoosyst. Evol. 100 (2) 2024, 583-595 587 Figure 2. Lateral view of 7. pratti (A) for IHB201909013758, 114.2 mm SL, Huili County, Sichuan Province, 7 truncatus (B) for IHB201812028889, 79.5 mm SL, Qianwei County, Sichuan Province, 7’ brachyrhabdion (C) for THB 2017090539, 120.8 mm SL, Songtao County, Guizhou Province, 7! gracilis (D) for IHB 201803023401, 98.2 mm SL, Guanyang County, Guangxi Zhuang Autonomous Region. be used to distinguish between them (Fig. 4). Zachysurus wuyueensis is distinct from the other three species in having a shorter prepelvic body (length 40.0-46.4% of HL vs. 45.8-54.8%; see Fig. 4A), from 7. truncatus and 7. gracilis in having more anal-fin rays (21—25 vs. 17—20) and vertebrae (45-47 vs. 37-43) (Fig. 5), from 7. trun- catus and T: brachyrhabdion in having a more slender body (depth 10.1-13.5% of HL vs. 13.1—20.6%; see Fig- ure 4B). It further differs from 7! truncatus in having a shorter pre-anal length (53.0-60.1% vs. 61.0-67.7%;Fig. AC), longer anal-fin base (length 25.4-31.1% SL vs. 19.1—25.5%, Fig. 4D), narrower mouth (width 8.1—10.6% SL vs. 10.0-13.7%; Fig. 4E), narrower interorbital space (width 5.0-7.9% SL vs. 8.7—10.5%; Fig. 4F) and from ZT. gracilis in having longer inner mandibular barbels (length 4.9-6.0% of SL vs. 3.2-5.0%; Fig. 4G). zse.pensoft.net 588 Jia-Jun, Z. et al.: A new Tachysurus species from the Qiantang-Jiang basin, China A @ T. wuyueensis B @ T. brachyrhabdion 4 © T. gracilis ®@® T. truncatus 3.2 2.4 1.6 vu ‘?) © 0.8 0 -0.8 -1.6 -2.4 4 32 -24 -16 08 O O08 16 24 3-25 -2 -15 -1 05 0 05 1° 15 PC1 PC2 Figure 3. Scatter plot of A. PC2 against PC3 and B. PC1 against PC2 extracted from morphometric data for 7) wuyueensis, T: trun- catus, T. brachyrhabdion and T: gracilis A 80 B @ 7. wuyueensis @ T. brachyrhabdion 70 © T. gracilis Uv co. @ T. truncatus ® 60 3° 3 a o < = a © 50 ie) a zB =| = © > 40 30 20 40 60 80 100 120 140 160 180 40 60 80 100 120 140 160 180 Standard length Standard length 4 = D> ° a: > — 5 = = @ oe =. a 7] to g : = = ® = =] a = = 60 80 100 120 140 160 60 80 100 120 140 160 Standard length Standard length G 7 F ° e — 6 . =] a e e a = 2 Ss mee = a? eee .* : : gi ea e Ea 2"o* ac ra = . e® * = @ =. oy : ° Qa | e . e > 3 =o oo 60 80 100 120 140 160 Standard length Standard length Figure 4. Relationship between A. Prepelvic length and SL for 7. wuyueensis, T: truncatus, T: brachyrhabdion and T. gracilis, rela- tionship between; B. Body depth and SL for 7) wuyueensis, T. truncatus and T. brachyrhabdion, relationship between; C. Pre-anal length and SL; D. Anal fin base length and SL; E. Mouth width and SL; F. Interorbital width and SL for 7? wuyueensis and T: trun- catus, relationship between; G. Inner mandibular barbel length and SL for 7! wuyueensis and T: gracilis. zse.pensoft.net Zoosyst. Evol. 100 (2) 2024, 583-595 A (OT. wuyueensis acts GT. truncatus , | a brachyrhabdion 40 al T. gracilis ei 38 39 AO 41 42 43 Ad 45 A6 AT Vetebrae number 589 No. °° 40 30 20 10 LA tS: PLOT Le BRO WAN g E21 tn UAB Te AA OZ Anal-fin rays number Figure 5. Meristic counts difference amongst 7? wuyueensis, T. truncatus, T: brachyrhabdion and T: gracilis in vertebrae number (A) and anal fin ray number (B). Tachysurus wuyueensis Zhou, Yuan & Shao, sp. nov. https://zoobank.org/18A 16B30-C113-4285-8A76-058999C3D0E1 Fig. 6 Pseudobagrus adiposis. Mao 1991: 169 (coastal rivers in Zhejiang Province). Type materials. Holotype. [HB 202009055690, 70.7 mm SL, South China: Zhejiang Prov.: Suichang County: the Qiantang-Jiang at Jiulongshan National Natural Reserve (28°23'38"N, 118°53'41"E) (Fig. 7); collected by Zhi- Gang Xie in Sept 2020. Paratypes. JHB = 202009055691-2, two ex., 63.8-65.2 mm SL; other data same as_ holotype. THB202212165294-304, 11 ex.,61.8—123.9 mm SL, south China: Anhui Prov.: Xiuning County: the Qiantang-Jiang at Liukou Township (29°48'57"N, 117°53'11"E) (Fig. 7); collected by Wei-Han Shao in May 2023. Diagnosis. Distinguished from its congeners by the following combination of characters: a smooth anterior margin of the pectoral-fin spine, short maxillary barbels not extending beyond the base of the pectoral-fin spine, short dorsal spine not exceeding two-thirds of head length, prepelvic length 40.0-46.4% SL, 45-47 verte- brae, 21—25 anal-fin rays, body depth 10.1—-13.5% SL, a slightly emarginated caudal fin. Description. Morphometric measurements taken from the holotype (78.7 mm SL) and 13 paratypes (61.8— 123.9 mm SL) summarised in Table 4. Body elongated, anteriorly cylindrical and slightly compressed posteriorly. Dorsal profile rising gradually from snout tip to dorsal-fin origin, then sloping evenly from there to posterior end of adipose-fin base, and grad- ually increasing to dorsal origin of procurrent caudal-fin rays. Ventral surface of head flattened; ventral profile of body straight or slightly rounded from head to anal-fin origin, decreasing evenly from posterior end of anal-fin base to origin of ventral procurrent caudal-fin rays. Lat- eral line complete, straight and mid-lateral in position. Vertebrae 5 + 45 (46, 47). Table 4. Morphomertric data for Tachysurus wuyueensis spe- cies nova. Holotype Paratypes (n = 13) Range Mean + SD Standard length 78.7 61.8-115.1 69.7 + 14.3 %SL Body depth at anus L312 10.1-13.5 13.1+41.5 Predorsal length 32.6 27.2-35.3 32.5+2.8 Pre-anal length 55.8 53.0-60.1 57.6+1.9 Prepelvic length 44.1 40.0-46.6 44.0+1.4 Prepectoral length 20.9 16.1-23.1 20.8+2.1 Length of dorsal-fin spine 59.2 46.4-63.8 59.2 + 3.3 Length of dorsal-fin base 11.4 8.6-11.7 11.3+1.3 Length of pectoral-fin spine 14.7 10.7-15.5 14.7+2.2 Length of anal-fin base 26.4 25.4-30.8 27.0+1.6 Height of adipose fin 3.1 2.4-5.1 4.1+0.9 Adipose to caudal distance 13.9 13.2-16.8 15.3421 Length of caudal peduncle 16.4 16.0-18.1 17.3+0.9 Depth of caudal peduncle 7.9 6.5-8.0 7.6+0.3 Head length at latera 22.8 17.9-24.8 23.74+2.5 Head depth lesz 9.0-13.2 12.3+1.5 Head width 14.2 13.1-15.7. 15.2+1.1 Snout length 5.5 4.2-8.7 6.0+1.9 Interorbital width 6.8 5.0-8.4 7.7413 Eye diameter 4.5 4.3-5.6 4.9+0.3 Mouth width 8.6 8.1-10.4 10.1+1.0 Length of nasal barbel 6.5 5.2-7.5 7.1414 Length of maxillary barbel 14.5 8.6-13.7 13.1 + 3.8 Length of inner mandibular barbel 6.0 4.6-6.6 6.1 +0.7 Length of outer mandibular barbel 9.5 5.9-10.7 9.6+2.1 Head depressed, broad, and covered with thin skin. Supra-occipital process slender, with evenly converg- ing sides and pointed tip, separated from nuchal plate by a broad interspace. Snout slightly pointed in dorsal view and obtuse or blunt in lateral view, longer than eye diameter. Interorbital space moderately space wide and slightly flattish. Eyes moderately large, ellipti- cal, covered with thick membrane and anterolateral in head, visible when viewed dorsally, but not ventrally, with slightly convex and comparatively narrow inter- orbital space. zse.pensoft.net 590 Jia-Jun, Z. et al.: A new Tachysurus species from the Qiantang-Jiang basin, China Figure 6. Lateral (A), dorsal (B) and ventral (C) views of 7Zachysurus wuyueensis species nova, IHB202009055690, holotype, 70.7 mm SL. Mouth subterminal, transverse. Upper jaw anteriorly protruded, longer than lower jaw in length; interorbit- al space narrower than mouth opening. Teeth villiform, in irregular rows on all tooth-bearing surfaces. Premax- illary tooth plates broad, of equal width throughout. Dentary tooth plates arched, broadest at symphysis and narrowing laterally, of same width at symphysis as pre- maxillary tooth plates. Vomerine tooth plate unpaired, continuous across mid-line, slightly curved anteriorly and much narrower than premaxillary plate. Gill open- ing wide, extending from the post-temporal region to beyond isthmus. Barbels in four pairs; nasal barbels small, thread-like, not reaching beyond posterior margin of eye; maxillary barbels slender, slightly exceeding posterior margin of eye; mandibular barbels in two pairs, thick, short, inner barbels positioned in transverse row at level of posterior naris, extending beyond mid-point of eye, outer barbels zse.pensoft.net rooted posterolateral to inner mandibular barbel, just ex- tending to posterior margin of eye. Dorsal fin with a spinelet, one spine and seven soft branched rays. Dorsal-fin origin equidistant to pecto- ral-fin insertion and ventrally to pelvic-fin insertion, also equidistant to anal-fin origin and snout tip. Spinelet flat- tened, with long blunt distal tip. Dorsal-fin spine slender, with smooth anterior margin and slightly serrated distal posterior margin, equal to or slightly longer than pecto- ral-fin spine. First dorsal-fin soft ray longest, surpass- ing tip of last ray. Distal margin of dorsal-fin rays nearly straight. Nuchal plate triangular, with anterior pointed tip anteriorly. Adipose fin inserted slightly behind vertical through pectoral-fin origin, with convex distal margin along entire length and deeply incised posterior part to form round- ed apex. Adipose fin base moderately long, equal to or slightly longer than anal fin base length. Zoosyst. Evol. 100 (2) 2024, 583-595 105°0'0"E 110°0'0"E 35°0'0"N-A 25°0'0"N PANS Legend Se. - @ T. wuyueensis sp. nov. * @ T. pratti @ T. truncatus 20°0'0"N5 © T. gracilis © T. brachyrhabdion 0 100 200 400 600 800 ) i a ees Kilometers Figure 7. Map showing distributions of five species of Zachysurus in China: 7: wuyueensis species nova, 7! pratti, T. truncatus, T. brachyrhabdion and T. gracilis. Pectoral fin with one spine and seven (or eight) soft branched rays, inserted slightly anterior or at level of posteriormost point of opercle, not reaching halfway to pelvic-fin insertion. Pectoral-fin spine very stout, sharp- ly pointed at tip, equidistant to or slightly longer than dorsal-fin spine, with a smooth anterior margin and 8 (9, mean 8.3) strong serrations along posterior margin. Cleithral process triangular with a sharp pointed tip, ex- tending for half of pectoral fin spine length. Pelvic fin with one unbranched and five branched soft rays, inserted closer to tip of snout than to posterior end of anal fin base, closer to depressed tip of dorsal fin than to anterior end of anal fin base. Tip of depressed pelvic fin reaching or slightly extending beyond anal fin origin. Pel- vic fin distal margin convex. Anus and urogenital opening nearer to anal fin origin than to posterior end of pelvic fin base. Males with a conical genital papilla not reaching base of first anal fin soft ray. Anal fin long, with 21 (22, 23, 25) branched rays; ad- ipose fin posterior margin away from caudal fin. Anal fin origin to caudal fin than to tip of snout. Distal margin of anal fin convex; anterior rays shortest. Caudal fin with 9+10 principal rays, slightly emargin- ated, with middle rays longer than two-thirds of longest rays; both lobes rounded, with upper lobe slightly longer than lower lobe; procurrent rays slightly extending from anterior to fin base. Lowest point of caudal peduncle be- hind posterior end of anal fin base. Colouration. Body yellowish-grey with three ob- scured and broad vertical brown blotches in smaller in- dividuals (the first one below the dorsal fin, the second one closely above the anal fin and the third occupying the aha 115°0'0"E 125°0'0"E Taiwan Island fr agra 2 iy caudal peduncle) (Fig. 6) and fading to a more uniform yellow or brown in larger individuals (Fig. 8). Adipose fin brownish, with a yellow anterodorsal margin and a slight- ly transparent posterodorsal margin. Dorsal fin trans- parent for anterior two-thirds, rest of fin greyish-brown. Caudal fin greyish in posterior third, rest of fin transpar- ent with a slightly white margin in smaller individuals. Pectoral, pelvic and anal fins transparent. Figure 8. A. Habitat of Zachysurus wuyueensis; B. T. wuyueen- sis in situ. Distribution and habitat. Currently only known from the Qiantang-Jiang in Suichang County, Zhejiang Prov- ince and Xiuning County, Anhui Province, south China (Fig. 7). [7 wuyueensis is found in montane streams of this river basin (Fig. 8), co-existing with Acrossocheilus fasciatus, Pseudogastromyzon fasciatus, Rhinogobius ni- ger and Tachysurus albomarginatus. zse.pensoft.net 592 Jia-Jun, Z. et al.: A new Tachysurus species from the Qiantang-Jiang basin, China Etymology. The specific epithet is based on the two ri- val states Wu and Yue which were bordered by the Qian- tang-Jiang in southeast China more than 2000 years ago. The onomatopoeic Chinese sound of this species 1s “Wu Yue Ni Chang”. Discussion Shao and Zhang (2023) erected the Zachysurus prat- ti group using morphological characters, such as smooth anterior margin of the pectoral spine, short maxillary-bar- bel not extending to the base of pectoral-fin, fewer than 20 anal-fins and uniform yellow or brown body in adults. Under this taxonomic treatment, the 7’ pratti group is the largest group within the genus, with more than twenty spe- cies. However, the monophyly of the 7 pratti group was not supported under the molecular scrutiny in this study (Fig. 1), indicating these species were wrongly clustered due to retention of conservative morphological features, common in catfishes (Zhou et al. 2016). Members in the 1. pratti group formed two distinct phylogenetic entities in our analyses: 77 wuyueensis clustering with 7. trunca- tus, T: pratti, T; gracilis and T: brachyrhabdion form a well-supported monophyletic clade, namely the 7 pratti-T: truncatus group, that is sister to 7. nitidus. The remaining species of the “7’ pratti group” form another monophyly here defined as the 7. tenuis-T: crassilabris group, sister to T. vachelli. In addition, the 7: pratti-T. truncatus group plus T. nitidus appears to be sister to a clade with 7: vachelli and T. tenuis-T: crassilabris group. Although the morphological similarities between these two newly-erected species groups are numerous, there are some distinguishing features that can be used to diagnose them. The 7: pratti-T. truncatus group differs from the T. tenuis-T. crassilabris group in having a shorter dorsal spine (length not longer than vs. longer than two-thirds of HL) (Figs 2, 9, 10). Differences in colour patterns were also found to be apparent between the two clades. The body colour of the 7: pratti-T: truncatus group 1s yellow- ish-brown (Fig. 2), but dark brown in the 7 tenuis-T. crass- ilabris group (Fig. 10). The distinction in colouration of the abdomen is conspicuous with numerous dark spots in the 7: tenuis-T. crassilabris group, but is absent in the 7. pratti-T: truncatus group (Fig. 11). In addition, the cau- dal-fin colouration of round-tailed species can be used as another diagnostic character between these two clades. Except for 7? tenuis, the white or yellowish caudal-fin margin is broad in the 7: tenuis-T: crassilabris group (Fig. 10), but which is narrow or absent in the 7. prat- ti-T. truncatus group (Fig. 2). The 7. pratti-T: truncatus group can also be distinguished from other species groups of Zachysurus in the external morphology. It differs from the 7! aurantiacus group, the 7? vachelli group and the T: trilineatus group in having short maxillary barbels not extending to (vs. extending beyond or reaching) the base of pectoral fin, from the 7: nitidus group, the 7! vachelli group and 7. virgatus group in having a dorsal fin spine shorter (vs. longer) than two-thirds of HL. zse.pensoft.net 45 @ T. pratti- T. truncatus group 40 @ T. tenuis-T. crassilabris group 35 30 25 ybus] suids-jesiop 10 15 20 25 30 35 40 45 HL Figure 9. Relationship between dorsal spine length and HL for the T: pratti-T. truncatus group (including 7? wuyueensis, T. prat- ti, T. truncatus, T. brachyrhabdion, T: gracilis) and the T. te- nuis-T. crassilabris group (including T. tenuis, T: albomargina- tus, T! analis, T. lani, T: zhangfei, T: ussuriensis, T: crassilabris). azar” " «” ™ Ms Me Figure 10. Lateral view of ZT. albomarginatus (A) for IHB 202110025885, 133.5 mm SL, Macheng County, Hubei Prov- ince; 7. analis (B) for IHB201707014311, 124.2 mm SL, Yudu County, Jiangxi Province, in Gan-Jiang; 7’ adiposalis (C) for FMNH 59079, holotype, 172 mm SL, Tamusui River, Taiwan Island; (D) Colour in life of adult of 7’ adiposalis, cited from Zhou and Gao (2011). The topotypes of 7’ adiposalis were not available in this study, but our photographic examination on the type (FMNH59079) confirmed that 7’ adiposalis has a long dor- Zoosyst. Evol. 100 (2) 2024, 583-595 993 Figure 11. Ventral view of 7. zhangfei (A) and T: gracilis (B) that belong to the 7) tenuis-T. crassilabris group and the T. pratti-T: truncatus group, respectively. sal-fin spine (longer than two-thirds of HL) and 19 anal- fin rays (Fig. 10C), which is distinct from 7. wuyueensis. Based on data from Taiwan, the dark brown body and wide white margin in the caudal fin are present in a living speci- men of 7: adiposalis (Fig. 10D) (Zhou and Gao 2011), sug- gesting this species may belong to the 7) tenuis-T. crass- ilabris group. Moreover, a phylogenetic analysis, based on a short segment of mtDNA, showed the specimens of T. adiposalis collected from Taiwan are closely related to 7. ussuriensis of the T. tenuis-T: crassilabris group. These data confirm our conclusion (Watanabe et al. 2007). High levels of inter-specific variations in the shape of the caudal fin occur in the 7’ pratti-T. truncatus group; for example, 7’ pratti has a deeply forked caudal fin, but the re- maining species of the group have round-tailed caudal fins. A similar scenario also occurs in the 7° tenuis-T. crassi- labris group. It suggests the convergent evolution of caudal fin morphology in Zachysurus. There is a tight link between the shape of the caudal fin and habitat preference: round- tailed species present habitat affinities to montane streams, while fork-tailed species are restricted to rivers’ main stream and lakes. The observation describes the effects of ecological niches by shaping the caudal fin in Zachysurus. Comparative materials examined 1. T. adiposis. FMANH59079, 170 mm SL, China: Ta- musui River in Taiwan Island. 2. Tachysurus albomarginatus: YHB200605264—7, 200605269-86, 220605268 72.1-128.5 mm SL, topotypes, China: Anhui Province: Dangtu County: the lower Yangtze River. . Tachysurus brachyrhabdion. 1HB2017090535-9, 107.6-121.8 mm SL, China: Guizhou Province: Songtao County, the Yuan-Jiang of middle Yangtze River Basin; IHB2017090522-—31, China: Chongq- ing City: Xiushan County, the Yuan-Jiang of the middle Yangtze River Basin; IHB2016106554, 6, 7, China: Hunan Province: Jishou County, the Yuan-Jiang of the middle Yangtze River Basin; THB2017090548-58, 588, China: Guizhou Prov- ince: Tongren City, the Yuan-Jiang of the middle Yangtze River Basin; IHB 201906012028—31, 104.0-127.3 mm SL, China: Hunan Province: Xupu County, the Yuan-Jiang of the middle Yang- tze River Basin; IHB2016106295—500, 104.4— 124.2 mm SL, China: Hunan Province: Mayang County, the Yuan-Jiang of the middle Yangtze River Basin; IHB2017090495-6, 135.3—150.1 mm SL, China: Guizhou Province: Jiangkou County, the Yuan-Jiang of the middle Yangtze River Basin; THB2017090427-34, 65.4-89.4 mm SL, China: Guizhou Province: Huangping County, the Yuan-Ji- ang of the middle Yangtze River Basin. . Tachysurus crassilabris (Gunther 1864): BMNH 1864.7.9.9 (holotype), 155.2 mm SL, China (photo- graph and X-ray examined); [HB 201909034566-9, zse.pensoft.net 594 Jia-Jun, Z. et al.: A new Tachysurus species from the Qiantang-Jiang basin, China 97.1-107.2 mm SL, China: Sichuan Province: Huili County: the Jinsha Jiang of the upper Yangtze Riv- er; IHB201909017347-61, 69.1-120.5 mm SL, China: Jiangsu Province: Nanjing City: the lower Yangtze River. 5. TI gracilis. 1HB201803023394-403, 93.6— 140.1 mm SL, China: Guangxi Zhuang Autono- mous Region: Guanyang County: the middle Yang- tze River Basin; IHB2017122195, 2017090542-6, 84.1-119.3 mm SL, China: Guangxi Zhuang Au- tonomous Region: Yangshuo County: the Pearl River Basin; IHB201909019374—83, 69.9-112.3 mm SL, China: Hunan Province: Shuangpai Coun- ty: the Xiang-Jiang of the middle Yangtze River Ba- sin; IHB201906011312, 175.9 mm SL, China: Hu- nan Province: Xinning County: the Zi-shui of the middle Yangtze River Basin; IHB201906011084, 132.0 mm SL, China: Hunan Province, Dongkou County, the Zi-shui of the middle Yangtze Riv- er Basin; IHB201906011497-503, 100.8—125.0 mm SL, China: Guangxi Zhuang Autonomous Region: Ziyuan County: the Zi-shui of the mid- dle Yangtze River Basin; [HB201809019719—22, 201809019850-1, 48.4—-138.8 mm SL, China: Yan- ling County, the Xiang-Jiang of the middle Yangtze River Basin. 6. Tachysurus tenuis: 1HB201909113617-13629, 124.5-159.6 mm SL, China: Zhejiang Province: Ji- axing City, the Qiantang-Jiang. 7. Tachysurus truncatus. 1HB201909038001-10, 84.9-109.5 mm SL, China: Sichuan Province: Wanyuan County, the Jialing-Jiang of the upper Yangtze River; [HB2019090112599-613, 76.0- 111.2 mm SL, China: Sichuan Province: Nanjiang County, the Jialing-Jiang of the upper Yangtze River; IHB201909037495—506, 20210505666—70, 73.6-123.5 mm SL, China: Hubei Province: Yu- an’an County, the Qing-Jiang of the middle Yang- tze River; IHB201904028989-96, 71.5—-138.8 mm SL, China: Hubei Province: Nanzhang County, the Han-Jiang of the middle Yangtze River Basin; THB2015030702-7, 70.6-124.2 mm SL, China: Hunan Province: Cili County, the Li-Shui of the middle Yangtze River Basin; IHB2017090517—21, 91.2-101.5 mm SL, China: Sichuan Province: Le- shan City, the Tuo-Jiang of the upper Yangtze River Basin; IHB201812028889-94, 65.7-124.4 mm SL, China: Qianwei County, the Tuo-Jiang of the up- per Yangtze River Basin; IHB2019090212127-45, 81.90-145.92 mm SL, China: Sichuan Province: Hejiang County, the Chishui-He of the upper Yang- tze River. 8. Tachysurus pratti: 1HB202009013755-64, 81.4— 143.8 mm SL, China: Sichuan Province: Huili County, the Jinsha-Jiang of the upper Yangtze Riv- er Basin; IHB2019090212149-55, 80.8-138.1 mm SL, China: Sichuan Province: Hejiang County, the Chishui-He of the upper Yangtze River Basin; zse.pensoft.net THB201909034750, 57.3 mm SL, Shuifu County, the Jinsha-Jiang of the upper Yangtze River Basin; THB202009016033-6, 48.8-56.0 mm, SL, China: Yunnan Province: Binchuan County, the Jinsha-Ji- ang of upper Yangtze River Basin. Conflict of interest The authors declare that they have no conflict of interest. Funding This work was partially funded by a grant from the Na- tional Science & Technology Fundamental Resourc- es Investigation Program of Mount Dabie (Grant No. 2019FY101800). Authors’ contributions Jia-Jun Zhou designed the study and revised the manu- script. Yuan Le-Yang extracted the genomic DNA and per- formed the molecular analysis. 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