Tachysurus wuyueensis Zhou, Yuan & Shao, 2024

Zhou, Jia-Jun, Yuan, Le-Yang & Shao, Wei-Han, 2024, Tachysurus wuyueensis (Teleostei, Bagridae), a new species of catfish from the Qiantang-Jiang basin, southeast China, Zoosystematics and Evolution 100 (2), pp. 583-595 : 583-595

Tachysurus wuyueensis Zhou, Yuan & Shao sp. nov.

Fig. 6

Pseudobagrus adiposis : Mao 1991: 169 (coastal rivers in Zhejiang Province).

Type materials.

Holotype. IHB 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. IHB 202009055691 - 2, two ex., 63.8–65.2 mm SL; other data same as holotype . IHB 202212165294 - 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 vertebrae, 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 gradually 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. Lateral line complete, straight and mid-lateral in position. Vertebrae 5 + 45 (46, 47).

Head depressed, broad, and covered with thin skin. Supra-occipital process slender, with evenly converging 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, elliptical, covered with thick membrane and anterolateral in head, visible when viewed dorsally, but not ventrally, with slightly convex and comparatively narrow interorbital space.

Mouth subterminal, transverse. Upper jaw anteriorly protruded, longer than lower jaw in length; interorbital space narrower than mouth opening. Teeth villiform, in irregular rows on all tooth-bearing surfaces. Premaxillary tooth plates broad, of equal width throughout. Dentary tooth plates arched, broadest at symphysis and narrowing laterally, of same width at symphysis as premaxillary tooth plates. Vomerine tooth plate unpaired, continuous across mid-line, slightly curved anteriorly and much narrower than premaxillary plate. Gill opening 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 rooted posterolateral to inner mandibular barbel, just extending to posterior margin of eye.

Dorsal fin with a spinelet, one spine and seven soft branched rays. Dorsal-fin origin equidistant to pectoral-fin insertion and ventrally to pelvic-fin insertion, also equidistant to anal-fin origin and snout tip. Spinelet flattened, 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 pectoral-fin spine. First dorsal-fin soft ray longest, surpassing 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 rounded apex. Adipose fin base moderately long, equal to or slightly longer than anal fin base length.

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, sharply 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, extending 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. Pelvic 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; adipose 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 emarginated, 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 behind posterior end of anal fin base.

Colouration.

Body yellowish-grey with three obscured and broad vertical brown blotches in smaller individuals (the first one below the dorsal fin, the second one closely above the anal fin and the third occupying the 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 slightly transparent posterodorsal margin. Dorsal fin transparent for anterior two-thirds, rest of fin greyish-brown. Caudal fin greyish in posterior third, rest of fin transparent with a slightly white margin in smaller individuals. Pectoral, pelvic and anal fins transparent.

Distribution and habitat.

Currently only known from the Qiantang-Jiang in Suichang County, Zhejiang Province and Xiuning County, Anhui Province, south China (Fig. 7 ). T. wuyueensis is found in montane streams of this river basin (Fig. 8 ), co-existing with Acrossocheilus fasciatus , Pseudogastromyzon fasciatus , Rhinogobius niger and Tachysurus albomarginatus .

Etymology.

The specific epithet is based on the two rival states Wu and Yue which were bordered by the Qiantang-Jiang in southeast China more than 2000 years ago. The onomatopoeic Chinese sound of this species is “ Wu Yue Ni Chang ”.

Figures

Figure 6. Lateral (A), dorsal (B) and ventral (C) views of Tachysurus wuyueensis species nova, IHB 202009055690, holotype, 70.7 mm SL.

Figure 7. Map showing distributions of five species of Tachysurus in China: T. wuyueensis species nova, T. pratti, T. truncatus, T. brachyrhabdion and T. gracilis.

Figure 8. A. Habitat of Tachysurus wuyueensis; B. T. wuyueensis in situ.