Oreonectes jinxiuensis sp. nov.

Oreonectes platycephalus, Zhu & Cao, 1987: 326 (Jinxiu County); Zhu 1989: 23‒24, fig. 12 (Jiuxiu County); Du et al. 2008: 29‒30, fig. 5 (Jiuxiu County).

Type material.

Holotype. KIZ 2005006221 (Kunming Natural History Museum of Zoology, KIZ, CAS), female, 48.9 mm standard length (SL), Fenzhan Village, Jinxiu Town, Yao Autonomous County, Laibin City, Guangxi Zhuang Autonomous Region, P. R. China; Liujiang River system of Pearl River basin; 24.120353°N, 110.214124°E. Collected by D. P. Kong and J. Yang on 15 October 2005.

Paratypes. KIZ 2005006212, KIZ 2005006219 –220, KIZ 2005006225 –228, seven specimens, male, 40.1–55.2 mm SL, KIZ 2005006212, KIZ 2005006229, female, 43.6–44.4 mm SL, same data as holotypes.

Other materials.

KIZ 20051015021, KIZ 20051015042 –44, same data as holotypes. KIZ 20051015058 –59, Laoshan Farm, Jinxiu Town, Yao Autonomous County, Laibin City, Guangxi; 23.90017°N, 110.13207°E. Collected by D. P. Kong and J. Yang in 15 October 2005.

Etymology.

The species name is derived from Jinxiu Town, Yao Autonomous County, Laibin City, Guangxi, where the specimens were collected. We suggest the Chinese common name as “金秀岭鳅.”

Diagnosis.

Comparative data between Oreonectes jinxiuensis sp. nov. and all 12 known species within the genus Oreonectes are provided in Table 2. This new species can be distinguished from all known species of Oreonectes by a combination of the following characteristics: color pattern presence; swim bladder degenerated; anterior and posterior nostrils adjacent; dorsal-fin origin posterior to pelvic-fin origin; tip of pelvic fin not reaching anus; 10 branched pectoral-fin rays; 14–15 branched caudal-fin rays; caudal fin without irregular black markings; caudal fin rounded; maxillary barbel not reaching posterior margin of opercula; 13 inner-gill rakers on first gill arch.

Description.

Morphometric and meristic data are given in Table 3. Body densely scaled include thorax and abdomen, body elongate and cylindrical (Fig. 1), body depth 15.4 % – 20.4 % of SL, slight elevation of head-dorsal junction, dorsal-fin origin closer to caudal-fin base than to posterior margin of opercula; head compressed, head width 65.6 % – 75.0 % of HL, head height 46.2 % – 56.2 % of HL; snout length shorter than postorbital length, snout length 33.1 % – 42.3 % of HL; mouth subterminal; inferior, slightly arched; upper lip smooth, only corners of mouth with slight wrinkles, lower lip wrinkles clearly visible, middle of lower lip separated by a V-shaped media notch, black pigmentation on upper lip, processus dentiformis absent; eyes normal, interorbital width greater than eye diameter; anterior and posterior nostrils adjacent, base of anterior nostril tubular, tip elongated to whisker-like; three pairs of barbels, inner rostral barbel reaching middle of eye; outer rostral barbel extending to posterior margin of eye; maxillary barbel extending to posterior margin of eye, not reaching posterior margin of opercula;

Four unbranched and seven branched dorsal-fin rays, one unbranched and 10 branched pectoral-fin rays; one unbranched and six branched pelvic-fin rays, three unbranched and five branched anal-fin rays, 14–15 branched caudal-fin rays. Dorsal fin origin posterior to pelvic-fin origin; pectoral fin length 58.5 % – 74.9 % of distance between pectoral fin and pelvic fin; tip of pelvic fin close to but not reaching anus; pelvic fin length 58.6 % – 73.0 % of distance between pelvic fin and anal fin; caudal-peduncle length similar to width, caudal-peduncle length 13.3 % – 16.4 % of SL, caudal-peduncle depth 12.8 % – 16.1 % of SL; caudal fin rounded, caudal fin without irregular black pigments.

Inner-gill rakers on first gill arch 12–13 (2); cephalic lateral line system well-developed, 7–9 + 3 – 4 infraorbital pores, 5–9 supraorbital canal pores, 3–4 supratemporal canal pores, 6–7 preoperculo-mandibular canal pores; lateral line incomplete, with 8–16 lateral-line pores.

Stomach U-shaped, intestine curved along stomach, leading directly to anus (Fig. 2 A). Posterior chamber of swim bladder degenerated, only 1.6 times eye diameter, a short tube (less than half the length of posterior chamber) connected two chambers of swim bladder (Fig. 2 B).

Sexual dimorphism.

Mature males have genital papilla located immediately posterior to anus, gonad opens at the end of fleshy prominence (Fig. 1 F), females do not have this characteristic.

Coloration.

In life, body yellowish-brown, with a distinct black longitudinal stripe extending along the lateral line (Fig. 1 G), In formalin-fixed specimens, body color faded, yet light yellowish brown and many obviously speckles, a longitudinal black stripe from dorsum of head to dorsal-fin base, the posterior margin of opercula has a longitudinal black stripe along the lateral line to anal fins, single dark brown vertical bar at caudal-fin base, all fins without speckles.

Distribution and habitat.

Oreonectes jinxiuensis sp. nov. is currently known from Jinxiu Town, Yao Autonomous County, Laibin City (24.120353°N, 110.214124°E) (Fig. 3 A), and Xiuren Town, Lipu City, Guilin (probably), Guangxi Zhuang Autonomous Region, China; mainly distributed in the Liujiang River system of the Pearl River basin in the Dayao Mountains area. This species inhabits small streamlets with water depths of about 0.5 m, characterized by abundant rocks and macrophytes around, providing good habitat for Oreonectes jinxiuensis sp. nov. (Fig. 3 B). Other species present in the streamlet include Acrossocheilus parallens, Rhinogobius giurinus, and Opsariichthys bidens.

Comparisons

Genetic comparisons. BI analysis of the constructed phylogenetic tree, based on a concatenated dataset of COI and Cyt b sequences, revealed consistent topologies. The phylogenetic tree confirmed the validity of the new species with high nodal support (BPP ≥ 0.95). Additionally, species within Oreonectes formed a monophyletic group, phylogenetically sister to the clade containing Guinemachilus and Micronemacheilus. Oreonectes jinxiuensis sp. nov. formed a highly supported clade with O. guilinensis and O. platycephalus (Fig. 4).

However, the O. platycephalus sequence DQ 105197 forms a distinct lineage separate from other O. platycephalus sequences in the phylogenetic tree. The taxonomic validity of this sequence requires further verification, and DQ 105197 was not included in this study’s sample and does not represent O. platycephalus discussed herein.

Genetic distances within the genus Oreonectes were calculated based on a concatenated dataset of mitochondrial COI and Cyt b (Table 4). The uncorrected p - distances between the new species and its congeners ranged from 4.1 % (O. guilinensis) to 10.6 % (O. guananensis), similar to values between other species in the same genus, such as 4.4 % between O. damingshanensis and O. zhangi, 4.7 % between O. qinae and O. zhangi, and 5.3 % between O. guananensis and O. luochengensis. Despite the close phylogenetic position of Oreonectes jinxiuensis sp. nov. and O. platycephalus on the BI tree, the p - distance between them (calculated using sequences ON 116528 and OR 396957, excluding DQ 105197) was 7.8 %. Substantial genetic divergence supports the conclusion that Oreonectes jinxiuensis sp. nov. represents a distinct species.

Morphological comparisons. Based on the results of PCA, two principal components of the morphological characters of Oreonectes jinxiuensis sp. nov. and O. guilinensis and O. platycephalus, which are phylogenetically close congeners of the new species, were extracted (Table 5). In the comparison between O. jinxiuensis sp. nov. and O. guilinensis and O. platycephalus (Fig. 5), the first principal component (PC 1), which accounted for 39.6 % of the variance, was influenced by predorsal length, pelvic length, pectoral-fin length, caudal-peduncle length, interorbital length; the second principal component (PC 2), which accounted for 24.5 % of the variance, was influenced by standard length, prepelvic length, preanal length, preanus length, postorbital length.

Oreonectes jinxiuensis sp. nov. can be distinguished from O. guilinensis by swim bladder degenerated (vs. developed), 8–16 lateral-line pores (vs. 4–6), a short tube (less than half the length of posterior chamber) connected two chamber of swim bladder (vs. a long, slender tube, exceeding half the length of posterior chamber and nearly equal to its full length), four unbranched and seven branched dorsal-fin rays (vs. two unbranched and six branched dorsal-fin rays), body width at front of dorsal fin 12.9 % – 16.0 % of SL (vs. 16.8 % – 18.8 %), body width at front of anal fin 5.8 % – 9.7 % of SL (vs. 10.5 % – 12.3 %), preanal length 73.7 % – 77.3 % of SL (vs. 77.5 % – 78.8 %), preanus length 66.1 % – 71.2 % of SL (vs. 72.1 % – 73.0 %), caudal-peduncle depth 12.5 % – 13.8 % of SL (vs. 10.5 % – 11.5 %), dorsal fin base to pelvic fin base 28.1 % – 32.0 % of SL (vs. 33.0 % – 35.9 %), pectoral fin length 18.1 % – 21.6 % of SL (vs. 14.6 % – 16.6 %), pelvic length 15.6 % – 18.7 % of SL (vs. 11.5 % – 13.4 %), eye diameter 16.4 % – 20.3 % of HL (vs. 12.1 % – 16.1 %).

Oreonectes jinxiuensis sp. nov. can be distinguished from O. platycephalus by four unbranched and seven branched dorsal-fin rays (vs. three unbranched and six branched dorsal-fin rays), six branched pelvic fin rays (vs. seven), a dark brown lateral stripe on both body sides presence (vs. absence), body width at front of dorsal fin 12.9 % – 16.0 % of SL (vs. 5.7 % – 10.8 %), head length 21.1 % – 24.3 % of SL (vs. 15.5 % – 19.4 %), caudal-peduncle length 13.3 % – 16.1 % of SL (vs. 10.2 % – 12.9 %), head width 15.3 % – 18.4 % of SL (vs. 10.7 % – 13.4 %). Morphological data of O. platycephalus following Ito (2024).

Oreonectes jinxiuensis sp. nov. formed a highly supported clade with O. guilinensis and O. platycephalus. Both p - distance and morphological data support the separation of the new species from these two species.