Oreonectes andongensis Luo, Yang, Du & Luo, 2024

Luo, Xue-Ming, Yang, Rui-Gang, Du, Li-Na & Luo, Fu-Guang, 2024, A new loach species of the genus Oreonectes (Teleostei, Cypriniformes, Nemacheilidae) from Guangxi, China, ZooKeys 1196, pp. 285-301 : 285

Oreonectes andongensis Luo, Yang, Du & Luo sp. nov.

, Figs 1 , 2 , 3 , 4 , 5

Type material.

Holotype. GXNU20220601, 74.9 mm standard length (SL), Andong Town, Xincheng County, Laibin City, Hongshui River system, Guangxi Zhuang Autonomous Region, China, 24°18.57'N, 108°59.61'E, 179 m a.s.l., collected by F.G.L., 20 July 2022. Paratypes. GXNU20220602-10, 9 specimens, 45.9-68.7 mm SL, same data as holotype.

Diagnosis.

The new species is assigned to the genus Oreonectes based on Cyt b phylogenetic analysis and morphological characters. The new species can be distinguished from other members of Oreonectes by the following combination of characters: posterior chamber of swim bladder developed (vs reduced in O. platycephalus ), color pattern present (vs colorless in O. luochengensis ), tip of pelvic fin not reaching anus (vs exceeding anus in O. polystigmus and O. guilinensis ), dorsal-fin origin slightly posterior to pelvic-fin origin (vs opposite in O. guananensis ), six branched pelvic-fin rays (vs 7 or 8 in O. damingshanensis , O. guananensis , O. luochengensis ). Oreonectes andongensis sp. nov. can be further differentiated from O. damingshanensis by more numerous, better developed inner gill rakers on the first gill arch (11-12 vs 9).

Description.

The morphometric data of the holotype and paratypes are in Table 1 . Three unbranched and seven branched dorsal-fin rays, one unbranched and nine or ten branched pectoral-fin rays, one unbranched and six branched pelvic-fin rays, three unbranched and five branched anal-fin rays, 13 or 14 branched caudal-fin rays, and 11 or 12 inner-gill rakers on first gill arch (in 3 specimens).

Body elongated and cylindrical, deepest body depth in front of dorsal-fin origin, deepest body depth 16-18% of standard length (SL). Head slightly depressed and flattened, maximum head width greater than deepest head height. Anterior and posterior nostrils adjacent, distance shorter than diameter of posterior nostril. Base of anterior nostril tube-shaped with elongated barbel-like tip; barbel longer than anterior nostril tube. Eyes normal, eye diameter 14-20% of head length (HL). Snout obtuse, snout length shorter than postorbital length. Mouth inferior, lips smooth, center of lower lip with notch. Three pairs of barbels, inner rostral barbel length 23-49% of HL, extending to the anterior margin of eye; outer rostral barbel length 50-70% of HL, extending to the posterior margin of eye; maxillary barbel length 43-56% of HL, not reaching to posterior margin of opercula.

Dorsal-fin origin slightly posterior to pelvic-fin origin. Predorsal length 58-62% of SL. Tip of pectoral fin not reaching half of distance between origin of pectoral and pelvic fins. Tip of pelvic fin not reaching anus. Short distance (two times eye diameter) between anal-fin origin and anus. Caudal fin straight. Caudal peduncle without adipose crests along both dorsal and ventral sides. Caudal peduncle depth 67-99% of caudal peduncle length. Whole body covered by scales except head. Lateral line incomplete, with 8-16 pores. Cephalic lateral line system developed, with 6-9 supraorbital pores, 3 + 8-10 infraorbital pores, three or four canal pores, and 6-8 pre-operculo-mandibular canal pores.

Stomach U-shaped. Swim bladder divided into two chambers, anterior chamber covered by dumbbell-shaped bony capsule, and posterior chamber developed with posterior extremely reaching below dorsal-fin origin.

Coloration.

In formalin-fixed specimens, dorsal surface and trunk of body yellowish, while abdomen appears grayish. Additionally, dorsal surface and flank with small spots or short bars. Dorsal and caudal fins with black speckles. Longitudinal stripe extending from gill opening to caudal peduncle in female, lacking in males.

Sexual dimorphism.

In reproductive season, males possess large genital papilla located immediately posterior to anus, unclear in females; gonad opens at end of fleshy prominence.

Distribution and habitat.

Oreonectes andongensis sp. nov. was collected from Andong Township, Xincheng County, Laibin City, Guangxi Zhuang Autonomous Region, China, a tributary of the Hongshui River in Xijiang River basin. During the rainy season, specimens were gathered from small pools on the surface where groundwater had overflowed. Troglonectes canlinensis Li et al., 2023 specimens were also collected from the same pool.

Etymology.

The nomenclature of this species is derived from the Chinese pinyin of Andong, the name of the village where the specimens were obtained. We suggest the Chinese common name as “安东岭鳅”.

Remarks.

Oreonectes andongensis sp. nov. can be distinguished from O. damingshanensis by the six branched pelvic-fin rays (vs 7), a dorsal-fin origin slightly posterior to pelvic-fin origin (vs posterior to pelvic-fin origin obviously), and 11 or 12 inner gill rakers on the first gill arch (vs 9), from O. guananensis by six branched pelvic-fin rays (vs 7 or 8), dorsal-fin origin slightly posterior to pelvic-fin origin (vs opposite to pelvic-fin origin), caudal with irregular black markings (vs without irregular black markings), and maxillary barbel not reaching to the gill cover (vs reaching to the gill cover), from O. guilinensis by lateral line pores 8-16 (vs 4-6), tip of pelvic fin not reaching to anus (vs exceeding to anus), and maxillary barbel not reaching to the opercula (vs reaching to posterior margin of the eye), from O. luochengensis by cephalic lateral line system present (vs absent), abdomen between pectoral-fin origin to pelvic-fin origin scaled (vs scaleless), from O. platycephalus by posterior chamber of swim bladder developed (vs reduced), dorsal-fin origin slightly posterior to pelvic-fin origin (vs posterior to pelvic-fin origin obviously), seven branched dorsal-fin rays (vs 8 or 9), and six branched pelvic-fin rays (vs 8), from O. polystigmus by tip of pelvic fin not reaching to anus (vs exceeding to anus), and maxillary barbel not reaching to the opercula (vs reaching to the pectoral-fin origin).

Figures

Figure 1. Bayesian phylogenetic tree of Oreonectes based on mitochondrial Cyt b. Numbers above branches are BPPs.

Figure 2. Oreonectes andongensis sp. nov. A-C lateral, dorsal and ventral views of holotype GXNU 20220601 (♀), D lateral view of paratype GXNU 20220610 (♂), E, F gonadal structure of female (E) and male (F).

Figure 3. Stomach, anterior chamber, and posterior chamber of Oreonectes andongensis sp. nov.

Figure 4. Distribution of Oreonectes in southern China.

Figure 5. Habitat of Oreonectes andongensis sp. nov.