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| Vanmanenia marmorata Deng & Zhang, 2021 DOI: 10.3897/BDJ.9.e72432 |
Abstract
Background:
The gastromyzontid genus Vanmanenia was established by Hora in 1932, based on the type species Vanmanenia stenosoma. The genus is a loach group adapted to running waters of streams from southern China, northern Vietnam and Laos. Currently, 19 valid species of the genus have been recognised. The northernmost distribution of the genus is the Yangtze River (= Chang-Jiang in Chinese) Basin and five species (V. maculata, V. intermedia, V. stenosoma, V. pseudostriata and V. gymnetrus) have been reported from the Basin.
New information:
Vanmanenia marmorata, a new hillstream species of loach, is here described from the middle Chang-Jiang Basin in Guizhou Province, south China. It is distinguished from its congeners by having a combination of the following characters: three triangular-shaped rostral lobules; postdorsal saddles wider than interspaces; a more backwards-placed anus (the vent to anal distance 30.5–36.9% of the pelvic to anal distance); a larger gill opening with its upper extremity reaching the level of the middle of the orbit; anal-fin base length 5.6–6.4% of SL; caudal-peduncle length 11.6–12.9% of SL; prepelvic length 51.1–53.4% of SL. Its validity is also affirmed by its distinct cyt b gene sequence divergence with all sampled congeners and its monophyly recovered in a cyt b gene-based phylogenetic analysis.
Keywords: freshwater fish, new taxon, morphology, cyt b gene, phylogenetic analysis
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| Vanmanenia marmorata, IHB2017060069, holotype, 68.8 mm SL; Guizhou Province: Jiangkou County. Lateral (a),dorsal (b) and ventral(c) views of body. |
Vanmanenia marmorata Deng & Zhang 2021, sp. n.
Diagnosis: Vanmanenia marmorata resembles the four species (V. caldwelli, V. maculata, V. intermedia and V. stenosoma) in having three triangular-shaped rostral lobules whose apical portions are in the barbel-like form, but not modified into secondary rostral barbels. It is distinct from these species in having postdorsal dark black saddles wider (vs. narrower) than their interspaces, further from V. caldwelli in having no longitudinal black stripe extending from the snout tip to the caudal-fin base along the lateral line on flank (vs. present) and a more backwards-placed anus [the vent to anal distance 30.5–36.9% (mean 34.6) vs. 60.0–70.3% (mean 68.5) of the pelvic to anal distance]; from V. maculata in having a dark black vermiculated mark (vs. large brown blotch; see Yi et al. 2014: Page 90, fig. 2) on the submargin of the gill cover and a more backwards-positioned anus [the vent to anal distance 30.5–36.9% (average 34.6) vs. 36.4–48.4% (average 43.0) of the pelvic to anal distance] (see Table 3); and from V. intermedia in having a larger gill opening with its upper extremity reaching the level of the middle of the orbit (vs. smaller, closer to the level of the lower margin of the orbit; see Deng and Zhang 2020 : Page 117: fig. 2), a shorter (vs. longer) anal-fin base [length 5.6–6.4 (mean 6.0) vs. 7.5–9.5 (mean 8.3) % of SL) and a longer (vs. shorter) caudal peduncle [length 11.6–12.9 (average 12.0) vs. 8.4–11.1 (average 9.9) % of SL]; and from V. stenosoma in having a longer (vs. shorter) caudal peduncle [length 11.6–12.9 (mean 12.0) vs. 9.0–11.1 (mean 10.0) % of SL] and a more forwards-positioned pelvic fin [prepelvic length 51.1–53.4 (mean 51.7) vs. 54.7–59.2 (mean 57.2) % SL].
Etymology: The specific epithet is from the Latin word marmor referring to the unique body colouration of irregular marbled markings.
Distribution: This new species is presently known from the upper reaches of the Chen-Shui, a stream tributary to the Yuan-Jiang of the Dongting Lake system in the middle Chang-Jiang Basin, at Jiangkou County, Guizhou Province, south China (Fig. 3). It inhabits fast-flowing waters with a gravelly and pebbly substrate (Fig. 4). Co-existing species are Discogobio yunnanensis (Regan, 1907), Onychostoma barbatum (Lin, 1931) and Rhinogobius cliffordpopei (Nichols, 1925).
Shuqing Deng and E. Zhang. 2021. Vanmanenia marmorata, A New Species of Loach (Teleostei: Gastromyzontidae) from the middle Chang-Jiang Basin in Guizhou Province, south China. Biodiversity Data Journal. 9: e72432. DOI: 10.3897/BDJ.9.e72432
