Oreonectes guidongensis Luo, Yu, Liao & Zhou, 2025

Oreonectes guidongensis Luo, Yu, Liao & Zhou sp. nov.

Tables 2 View Table 2 , Fig. 4 A – D View Figure 4 , Suppl. material 1, 2

Chresonymy.

Oreonectes polystigmus : Fuli Town and Xinhua Town, Fuchuan County, Guangxi, China ( Lan et al. 2013); Jianghua County, Yongzhou City, Hunan, China ( Yu et al. 2023; Lan et al. 2024; Luo et al. 2025); and Fuchuan County, Hezhou City, Guangxi, China ( Yu et al. 2023; Lan et al. 2024; Luo et al. 2024 a; Luo et al. 2025).

Holotype.

GZNU 20241127001 , 63.5 mm TL, 51.7 mm standard length (SL), collected by Jing Yu on March 31, 2024, in Lianshan Town , Hezhou City, Guangxi Zhuang Autonomous Region, China ( 24.75929000°N, 111.3524400°E; ca. 194 m a. s. l.). GoogleMaps

Paratypes.

Seventeen specimens from the same locality as the holotype: GZNU 20240331007 , GZNU 20240331012 –0331018, GZNU 20240531001 –0531005, 45.9–59.6 mm SL, collected by Jing Yu and Tao Luo in March and May 2024. GZNU 20241127002 –1127005, 42.5-59.0 mm SL, collected by Jing Yu and Mei Liao in November 2024.

Etymology.

The species name “ guidongensis ” refers to its distribution in Guangxi (广西), also known as Gui (桂), specifically indicating that the species is found in the eastern region of Guangxi, China. The suggested English name for this species is the Guidong Hilly Loach, and its Chinese name is Guì Dōng Lǐng Qiū (桂东岭鳅).

Diagnosis.

Comparative data between new species and all nine known species within the genus Oreonectes are provided in Table 4 View Table 4 . Oreonectes guidongensis sp. nov. can be distinguished from O. platycephalus and O. zhangi by the well-developed posterior chamber of air bladder (vs. reduced), from O. damingshanensis , O. guananensis , and O. luochengensis by six branched plevic-fin rays (vs. 7 or 7–8), from O. guilinensis and O. yuedongensis by seven branched dorsal-fin rays (vs. 6), from O. andongensis 10 inner gill rakers on the first gill arch (vs. 11–12), and from O. polystigmus by the tip of pelvic fin not reaching the anus (vs. reaching the anus), distance between the posterior base of the pectoral fin and the anterior base of the pelvic fin is 18.8–27.9 % of standard length (18.8–27.9 % HL vs. 27.9–34.1 %), and five supratemporal pores (vs. 3) (Figs 4 View Figure 4 , 5 View Figure 5 ).

Description.

Morphometric data are given in Table 2 View Table 2 and Suppl. material 1. Dorsal-fin rays iii- 7, pectoral-fin rays i- 10, pelvic-fin rays i- 6, anal-fin rays iii- 5, 14-16 branched caudal-fin rays, and 10 inner gill rakers on the first gill arch.

Body elongated and cylindrical, deepest body depth in front of dorsal-fin origin, deepest body depth of 13.3–17.6 % SL, with the insignificant depth decreasing from dorsal-fin origin to caudal-fin base. Head short, slightly depressed and flattened, maximum width greater than deepest depth (head width / head depth = 1.2–1.7). Snout round, oblique, and flat, length 36.0–43.2 % of head length (HL). Mouth inferior, curved, upper and lower lips smooth, lower lip with a V-shaped median notch. Three pairs of barbels are long: inrostral barbel length 28.1–47.3 % of HL, tips reaching the anterior margin of the eye; outrostral barbel length 45.6–68.6 % of HL, tips beyond the posterior margin of the eye. Maxillary barbel length 37.5–59.0 % of HL, tips not reaching to the posterior margin of the gill cover. Anterior and posterior nostrils narrowly separated, with an interspace of approximately 1.2 mm. Anterior nostril tube short, with an elongated short barbel-like tip. Eyes normal, diameter of 10.1–16.9 % HL. Gill opening small; gill rakers not developed, and 10 inner gill rakers on the first gill arch.

Dorsal fin short, length 16.9–21.7 % of SL, pre-dorsal length 58.6–62.5 % of SL, distal margin round, origin posterior to pelvic-fin origin. Pectoral fin short, length 16.7–20.5 % of SL, pre-pectoral length 21.1–24.9 % of SL, tips reaching about half of the distance between the origin of pectoral and pre-pelvic fins. Pelvic-fin length 14.0–16.9 % of SL, pre-pelvic length 51.7–56.5 % of SL, tips not reaching the anus. Anal fin long, length 15.1–18.4 % of SL, tips not reaching the caudal-fin base. Caudal fin rounded, caudal peduncle length 11.6–16.6 % of SL, without adipose crests along either dorsal or ventral sides.

Body completely covered with fine scales, except for head, thorax, and abdomen. Lateral line incomplete, exceeding tip of pectoral fin but not reaching the caudal fin base, with 6–10 pores, last lateral line pore not reaching the tip of pectoral fin. Cephalic lateral-line system, with 7–8 supraorbital, 4 + 11 infraorbital canal pores, 5 supratemporal canal pores, with 6–7 preoperculo-mandibular canal pores (Fig. 5 A 1 – A 3 View Figure 5 ). Stomach U-shaped with straight intestines (Fig. 4 D View Figure 4 ). Anterior chamber covered by dumbbell-shaped bony capsule, posterior chamber well-developed, and tube connecting anterior and posterior chambers of the air bladder (Fig. 4 E View Figure 4 ). Lateral wall of the bony capsule of the swim bladder is membranous and closed posteriorly (Fig. 4 E View Figure 4 ).

Sexual dimorphism.

In males, a genital papilla is present immediately posterior to the anus, with the gonopore opening at the tip of a fleshy prominence (Fig. 5 C 1, C 2 View Figure 5 ).

Coloration.

In life, overall body light yellowish brown with many obvious speckles, dark brown between anterior margin of eyes to outrostral barbel; dorsum with irregular brown spots; dorsal and caudal fins dark brown at base (Fig. 6 A View Figure 6 ). In 10 % formalin the body color was dark brown.

Distribution, habitat, and populations.

Based on recent surveys, the new species Oreonectes guidongensis sp. nov. is widely distributed in streams of Fuchuan County, Hezhou City, Guangxi, China, within the Guijiang – Heijiang River basin of the Pearl River system. It is also found in Jianghua County, Yongzhou City, Hunan Province (Fig. 1 View Figure 1 ). The species occurs in large populations in its known habitats and is relatively easy to collect.

Morphological comparison with the congeners.

Comparative data of Oreonectes guidongensis sp. nov. with the nine recognized species within the genus Oreonectes are given in Table 4 View Table 4 .

Oreonectes guidongensis sp. nov. can be distinguished from O. luochengensis by body pigmentation absent (vs. present), 10 branched pectoral-fin rays (vs. 11–12), six branched pelvic-fin rays (vs. 7), and ten inner gill rakers on the first gill arch (vs. 13–14).

Oreonectes guidongensis sp. nov. can be distinguished from O. zhangi , O. yuedongensis , and O. damingshanensis by 10 branched pectoral-fin rays (vs. 8–9). Oreonectes guidongensis sp. nov. can be further distinguished from O. zhangi by 10 inner gill rakers on the first gill arch (vs. 9) and developed posterior chamber of air bladder (vs. reduced); from O. yuedongensis by seven branched dorsal-fin rays (vs. 6) and tip of pelvic fin not reaching the anus (vs. reaching the anus); and from O. damingshanensis by six branched pelvic-fin rays (vs. 7) and 10 inner gill rakers on first gill arch (vs. 8).

Oreonectes guidongensis sp. nov. can be distinguished from O. guananensis by six branched pelvic-fin rays (vs. 7–8), 10 inner gill rakers on the first gill arch (vs. 11), and body with obvious speckles (vs. absent); from O. guilinensis by seven branched dorsal-fin rays (vs. 6); from O. platycephalus by seven branched dorsal-fin rays (vs. 6), six branched pelvic-fin rays (vs. 7), and developed posterior chamber of air bladder (vs. reduced); and from O. andongensis by 10 inner gill rakers on the first gill arch (vs. 11–12).

Oreonectes guidongensis sp. nov. is phylogenetically and morphologically close to O. polystigmus but can be distinguished by a combination of the following characters: tip of pelvic fin not reaching anus (vs. reaching anus) (Fig. 5 View Figure 5 ), distance between the posterior base of the pectoral fin and the anterior base of the pelvic fin is 18.8–27.9 % of standard length (vs. 27.9–34.1 %), cephalic lateral-line system, and five supratemporal pores (vs. 3). In addition, the new species and O. polystigmus showed significant differences in 47 % of the 34 morphological characters measured, including total length, predorsal length, pectoral fin length, pelvic fin length, pelvic fin base length, anal fin length, anal fin base length, distance between anal fin and posterior margin of anus, distance between pectoral and pelvic fins, distance between pectoral and anal fins, preanterior nostril length, head width, out rostral barbel length, maxillary barbel length, eye diameter, and mouth width (Suppl. material 2).