Karstsinnectes cehengensis Luo, Zhao & Zhou, 2024

Zhao, Xinrui, Lan, Changting, Luo, Tao, Yu, Jing, Zhou, Jiajun, Xiao, Ning & Zhou, Jiang, 2024, Karstsinnectes cehengensis (Cypriniformes: Nemacheilidae), a new species of cave fish from Guizhou, China, Zoological Systematics 49 (2), pp. 101-115 : 107-112

Karstsinnectes cehengensis Luo, Zhao & Zhou , sp. nov. ( Figs 3–4 , Table 4)

Material examined. Holotype. GZNU20230106002 ( Fig. 3 ), 47.8 mm total length (TL), 39.9 mm standard length (SL), Bayan Village , Rongdu Town, Ceheng County, Guizhou Province, China (105.72195053E, 25.11225901N, elev. 1259 m; Fig. 1 ), January 6, 2023, coll. Tao Luo. Paratypes. Five specimens, same locality as holotype, GZNU20230215002–0215006 , February 15, 2023, coll. Tao Luo, Xinrui Zhao.

Etymology. The specific epithet “ cehengensis ” is in reference to the type locality of the new species, Ceheng County. We propose the common English name “Ceheng Chinese Karst Loach” and Chinese name “Cè Hēng Zhōng Huá Kā qiū (¶ 亨中华喀#)”.

Diagnosis. The new species can be distinguished from all other congeners by the following combination of characters: (1) body naked, without body color; (2) eyes reduced, diameter 1.4–3.8% of head length; (3) anterior and posterior nostrils adjacent, anterior nostril not elongated to a barbel-like tip; (4) lateral line incomplete; (5) caudal fin forked;(6) dorsal-fin rays iii-7, pectoral-fin rays i-11–12, pelvic-fin rays i-7, anal-fin rays iii-5, with 14 branched caudal-fin rays.

described in this study.

Description. Morphological data see Table 4. Body elongated and cylindrical, anterior portion gradually raised from upper eye to dorsal fin base, posterior portion gradually compressed from dorsal fin to caudal-fin base, with deepest body depth anterior to dorsal-fin origin, deepest body depth 13–15% of standard length (SL). Dorsal profile slightly convex from snout to dorsal-fin insertion, deepest concavity downward above anal fin. Ventral profile flat. Head short, length of 24–26% of SL, slightly depressed and flattened, width greater than depth (head width/head depth: 109–128%). Snout short, lightly blunt, length 40–43% of head length (HL). Mouth inferior and curved, mouth corner situated below anterior nostril, upper and lower lips smooth, lips thick with shallow furrows, lower lip with a V-shaped median notch. Upper and lower jaw arched. Three pairs of barbels: inrostral barbels short, length 7–25% of HL, backward not extending to corner of mouth; outrostral barbel long, length 38–47% of HL, backward extending reaching to posterior margin of eye. Maxillary barbel slight developed, length 21–32% of HL, tip of maxillary barbel not reaching to anterior margin of operculum. Anterior and posterior nostrils adjacent, length 0.2–0.5 mm, 150–517% of eye diameter. Anterior nostril tube long, truncated, without elongated short barbel-like tip. Eyes reduced, with diameter 1–4% of HL. Gill aperture small, gill rakers not developed, nine inner gill raker on first gill arch (n = 3).

Dorsal-fin rays iii-7, pectoral-fin rays i-11–12, pelvic-fin rays i-7, anal-fin rays iii-5, with 14 branched caudal-fin rays. Dorsal fin short, length 17–20% of SL, distally margin truncated, origin slightly posterior to pelvic-fin insertion, situated slightly posterior to midpoint between snout tip and caudal-fin base, first branched ray longest, shorter than head length, tip of dorsal fin beyond to vertical of anus. Pectoral fin moderately developed, length 18–20% of SL, tip of pectoral fin extends backwards beyond midpoint between origin of pectoral and pelvic fin origins, not reaching to pelvic fin origins. Pelvic fin length 13–14% of SL, distally margin oval, vertically aligned with first unbranched ray of dorsal fin, tips of pelvic fin not reaching to anus. Anal fin long, length 14–16% of SL, origin close to anus, tips of anal fin not reaching caudal-fin base. Caudal fin forked, upper lobe is equal in length to lower one, tips pointed, caudal peduncle length 15–17% of SL, caudal peduncle depth 53–61% of body depth, with slight developed adipose crests along both dorsal and ventral sides. Total vertebrae: 39 (n = 3).

Body naked, smooth, and scaleless. Cephalic lateral line system developed. Lateral line complete, exceeding tip of pectoral fin and reaching base of caudal fin. Two chambers of air-bladder, anterior chamber dumbbell-shaped and membranous, open on both sides and posteriorly ( Figs 4A–B ), and posterior chamber developed, slight filling body cavity, connected with anterior chamber by short tube.

Coloration. In cave water bodies when living, body semi-translucent and pale pink, without skin pigment, and all fins hyaline ( Fig. 5 ). After fixation in 7% formalin solution, body yellowish white, thorax and gills light brown color, transparent on all fins ( Fig. 3 ).

Comparisons. Morphological data of all species of Karstsinnectes see Table 5. Although the new species shares some characteristics with its congeners, such as the absence of body coloration, scaleless, and dorsal-fin origin slight posterior to ventral-fin origin, it can be distinguished from them by a combination of series of morphological characters.

The new species can be distinguished from K. anophthalmus and K. acridorsalis by eyes reduced (vs. absent), lateral line incomplete (vs. degraded or absent), 2 unbranched pectoral-fin rays (vs. single). It is further distinguished from K. anophthalmus by 3 unbranched anal-fin rays (vs. 2), 3 unbranched dorsal-fin rays (vs. 2), 3 unbranched anal-fin rays (vs. 2), and 14 branched caudal-fin rays (vs. 13); and from K. acridorsalis by 7 branched dorsal-fin rays (vs. 8–9), 2 unbranched pectoral-fin rays (vs. single), and 7 branched pelvic-fin rays (vs. 6).

The new species can also be distinguished from K. parvus and K. hyalinus by eyes reduced (vs. absent), 2 unbranched pectoral-fin rays (vs. single), 7 branched pelvic-fin rays (vs. 6 or 5–6). It is further distinguished from K. parvus by 7 branched dorsal-fin rays (vs. 9–10), and 14 branched caudal-fin rays (vs. 15); and distinguished from K. hyalinus caudal-fin shape forked (vs. concaved), body naked (vs. body with tiny scales), 2 unbranched pectoral-fin rays (vs. single), and 7 branched pelvic-fin rays (vs. 5–6).

Ecology and distribution. At present, this new species is only found in a cave in Bayan Village , Rongdu Town , Ceheng County, Guizhou Province, China, at an elevation of 1259 m, in the water system of the Beipanjiang River . The pool where the new species was found is more than 500 cm long, 50 cm wide and 80 cm deep, with a slow water flow. Inside the cave, frogs (tadpoles of Oreolalaxrhodos tigmatus), bats (Ia io, six individuals) and crabs (Diyutamoncereum, three individuals) have been found. Outside the cave, local farmers have built houses and planted orange trees. The number of this new species is very low, with a total of 10 specimens from two surveys .

Key characteristics K. cehengensis sp. nov. K. anophthalmus K. acridorsalis K. parvus K. hyalinus

Eyes Reduced Absent Absent Absent Absent

Caudal-fin shape Forked Rounded Forked Forked Concave

Body Scales Absent Absent Absent Absent Tiny scales

Lateral line Incomplete Degraded Absent Complete Incomplete

Dorsal-fin rays iii, 7 ii, 7 iii, 8–9 iii, 9–10 iii, 7–8

Anal-fin rays iii, 5 ii, 5 iii, 5–6 iii, 5 iii, 5

Pectoral-fin rays ii, 11–12 i, 10–12 i, 10–12 i, 10–11 i, 10–12

Pelvic-fin rays i, 7 i, 4–5 i, 6 i, 6 i, 5–6

Caudal-fin rays 14 12–13 13–14 15 14–15

Anterior nostril No No No No Yes barbell-like

Anterior and Slightly separated Slightly separated Slightly separated Closely set Closely set posterior nostrils

Distribution Beipanjiang River Zuojiang River; Hongshui River Youjiang River Hongshui River Youjiang River

Source This study This study; Lan et Lan et al., 2013 Zhu & Zhu, 2014 Lan et al., 1996 al., 2013

Figures

Figure 1. Distribution of the species of Karstsinnectes in Southwest China, with its potential distribution regions.

Figure 3. Morphological characteristics of holotype GZNU20230106002 of Karstsinnectes cehengensis Luo, Zhao & Zhou, sp. nov. in preservative (10% formalin), photographed by Tao Luo. A. Latera view; B. Dorsal view; C. Ventral view. Scale bars=5.0mm.

Figure 4. The three-dimensional reconstructed model of the skeleton of Karstsinnectes cehengensis Luo, Zhao & Zhou, sp. nov. (paratype GZNU20230223003, standard length 33.5mm). A. Dorsal view; B. Ventral view; C. Latera view.

Figure 5. Karstsinnectes cehengensis Luo, Zhao & Zhou, sp. nov. (A–B) and K. anophthalmus (C) in life. A from holotype GZNU2023 0106002. A, C were photographed by Tao Luo, B by Jiajun Zhou.