Cobitis xui, Tan & Li & Wu & Yang, 2019

Tan, Xi-Chang, Li, Peng, Wu, Tie-Jun & Yang, Jian, 2019, Cobitis xui, a new species of spined loach (Teleostei: Cobitidae) from the Pearl River drainage in southern China, Zootaxa 4604 (1), pp. 161-175 : 164-167

publication ID	https://doi.org/ 10.11646/zootaxa.4604.1.6
publication LSID	lsid:zoobank.org:pub:97E78169-44DD-490D-B29C-2A7B0379FF3A
persistent identifier	https://treatment.plazi.org/id/03D087CE-FFDD-FF89-128C-61BAFAD6FDB9
treatment provided by	Plazi
scientific name	Cobitis xui
status	sp. nov.

Treatment

Cobitis xui sp. nov.

( Figs. 2‒5 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 )

Holotype. GTEU 201705001 , male, 61.8 mm SL. China: Guangxi, Rong’an County, Buquan Town, Buquan River , Youjiang basin, 23°4.35′N; 107°28.0′E, alt 261 m, leg. Jiahu Lan, May 2017. GoogleMaps

Paratypes. 7 ex. GTEU 201705002‒201705008 , females, 63.4‒75.1 mm SL ; data same as holotype GoogleMaps .

Diagnosis. Cobitis xui sp. n. is distinguished from the other species of Cobitis in China by the following combination of characters, none of them unique: snout blunt; body depth 14.3‒18.4% SL; the longest dorsal-fin ray length shorter than HL; lamina circularis long and knife-shaped in males; mental lobes of the lower lip developed and each lobe split into three notches with pointed tip; five longitudinal lines of dark spots on the dorsolateral sides of body; 8‒11 transverse blotches on L5; 9‒12 transverse blotches on L1; second maxillary barbels longer than eye diameter; 4‒5 narrow rows of dark spots on the caudal fin; caudal fin with 14 branched rays; a rectangular spot slightly smaller than eye diameter on the upper lobe of caudal fin base; and caudal-peduncle depth 53.6‒70.6% its length.

Description. Morphometric data of holotype and paratypes presented in Table 2 View TABLE 2 . For general appearance see Figs. 2‒3 View FIGURE 2 View FIGURE 3 . Body elongated, laterally compressed. Dorsal profile of head convex. Abdomen laterally rounded. Greatest body depth occurs at insertion of dorsal fin. Predorsal length longer than post-dorsal length. Head small, head length 19.5‒21.8% SL in females, 22.6% SL in male. Snout blunt, snout length 41.2‒48.6 %HL in females, 39.7 % HL in male. Anterior and posterior nostrils closely situated; anterior ones with circular nostril tube ( Fig. 4 View FIGURE 4 ). Eyes small, superolaterally placed; interorbital width narrower than eye diameter. Suborbital spine bicuspid with small latero-caudalis processus laterally situated under eye ( Fig. 5 b View FIGURE 5 ). Mouth small, inferior, with fleshy lips; upper lips with weak transverse wrinkles on surface; lower lip divided with two well-developed lobes, each lobe split into three notches ( Fig. 4 View FIGURE 4 ). Three pairs of barbels; rostral barbel short, tip of inner rostral barbel not reaching vertical line of anterior margin of nostrils; maxillary barbel long, 18.1‒23.2 % HL, reaching vertical line of anterior margin of eyes. Body scales small, round, with medium focal area situated closer to base, each with 26‒28 radial grooves ( Fig. 5 a View FIGURE 5 ). Lateral line short, ending at anterior edge of second blotches of L 5.

Dorsal fin with three unbranched and seven branched rays, outer margin slightly convex; length of longest dorsal-fin ray shorter than HL. Pectoral fin with one unbranched ray and eight branched rays. Pelvic fins short with 6 branched rays, its origin opposite base of second branched dorsal-fin ray. Anal fin small with five branched rays. Caudal fin truncate, long, with 14 branched rays. Distance between anus and anal-fin origin shorter than eye diameter.

Colouration and pigmentation pattern. Body light yellow. Head sprinkled with numerous minute black spots; black stripe extends from occiput through eye to base of rostral barbel. Five longitudinal lines of dark spots on dorsolateral sides of body (Gambetta pigment pattern, L1‒L5) ( Figs. 2‒3 View FIGURE 2 View FIGURE 3 ). L 1 composed of 9‒12 rectangular brownish blotches, the gaps between the blotches narrower than their lengths. L 2 characterised by row of discontinuous brownish patches melted into stripe, stripe diminished toward dorsal-fin origin. L 3 with row of eyediameter sized small rectangular or circular blotches, ending at caudal-fin base. L 4 consists of line of minute brownish spots, postdorally confluent with L 2 and L 3. L 5 with row of eight blotches (five longitudinal rectangular blotches, last three circular blotches) in male; 10‒12 longitudinal rectangular blotches (last three circular blotches) in females. One conspicuous black rectangular spot on the dorsal side of caudal-fin base; this spot is smaller than eye diameter. Dorsal fin and caudal fin with scattered brownish spots, forming four stripes on dorsal fin and five stripes on caudal fin.

Sexual dimorphism. Male smaller than females. In single male, pectoral fins longer than those in females, first branched pectoral-fin ray longest, its length 22.1% SL. In females, second branched pectoral-fin ray longest, its length 12.9‒14.9 % SL. Caudal peduncle in male deeper than in females, caudal-peduncle depth 53.6‒67.2% SL in females (vs. 70.6% in male). In male, first branched pectoral-fin ray thickened and elongated, with long knifeshaped lamina circularis on second and third branched pectoral-fin rays ( Figure 4 c, d View FIGURE 4 ).

Distribution, habitat, and ecology. Cobitis xui is found in the Buquan River in Rong’an County, Guangxi, China, Youjiang basin, belonging to the Pearl River drainage ( Fig. 6 View FIGURE 6 ). At the relevant section of the Buquan River, the current was medium to fast, the river width was between 25‒60 m, and the maximum depth was approximately three meters, with the river bed composed of cobbles and gravel. The following fish species co-exist with C. xui at the type locality: Schistura fasciolata (Nichols & Pope) ; Misgurnus anguillicaudatus (Cantor) ; Opsariichthys bidens Günther ; Pseudorasbora parva (Temminck & Schlegel) ; Squalidus argentatus (Sauvage & Dabry de Thiersant) ; Acheilognathus tonkinensis (Vaillant) ; Puntius semifasciolatus (Günther) ; Spinibarbus denticulatus (Oshima) ; Spinibarbus caldwelli (Nichols) ; Rectoris posehensis Lin ; Osteochilus salsburyi Nichols & Pope ; Cirrhinus molitorella (Valenciennes) ; Cyprinus carpio Linnaeus ; Carassius auratus (Linnaeus) ; Silurus asotus Linnaeus and Clarias fuscus Lacepède.

Etymology. The new species is named in honour of Xiake Xu, a travel writer and geographer of the Ming Dynasty in China, best known for his famous geographical treatise. He travelled throughout China for more than 30 years, especially in the Pearl River basin.

Phylogenetic analysis. Phylogenetic trees constructed using two different phylogenetic methods are shown in Figure 7 View FIGURE 7 (BI) and Figure 8 View FIGURE 8 (ML). Topologies of the trees are similar. There were 6 lineages resolved using both BI and ML method, which is similar with previous studies (Chen & Chen 2013, Chen et al. 2015). However, the positions of C. obtusirostra and C. macrostigma are different in topology between the BI and ML analyses. In the two trees, there is strong support (Bayesian posterior probability = 1.00 and bootstrap support value = 100) for both individuals of the new species C. xui forming a monophyletic clade. Conspecific individuals of Cobitis xui , C. wumingensis , C. baishagensis , C. australis , C. leptosoma and C. heteromacula co-cluster forming clade E. The new species has a sister relationship with C. wumingensis , with a genetic distance of 2.99% (Table 3).