Revalidation and redescription of a gobionine species Microphysogobio bicolor (Nichols, 1930) (Teleostei: Cypriniformes) from the Yangtze River Basin, China Author Sun, Zhixian 0000-0003-0565-2801 Key Laboratory of Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences, Beijing, China 201600210039 @ mail. sdu. edu. cn; https: // orcid. org / 0000 - 0003 - 0565 - 2801 201600210039@mail.sdu.edu.cn Author Zhao, Yahui 0000-0003-0565-2801 Key Laboratory of Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences, Beijing, China 201600210039 @ mail. sdu. edu. cn; https: // orcid. org / 0000 - 0003 - 0565 - 2801 201600210039@mail.sdu.edu.cn text Zootaxa 2022 2022-01-20 5092 3 361 377 journal article 2457 10.11646/zootaxa.5092.3.7 6be50ef6-56ce-474a-955a-6098e2bd9985 1175-5326 5881381 305C0669-2FA4-45AE-ABB6-180C13A2F795 Microphysogobio bicolor ( Nichols, 1930 ) ( Fig. 1 , 2 ) Pseudogobio bicolor Nichols : 1, (original description); Nichols (1943) , 182. Holotype . AMNH 9678 , 59.8mm standard length (SL); China : northeastern Kiangsi (= Jiangxi Province ), Hokou (= Hekou Town ); collected by Clifford H. Pope ; 22 June 1926 . TABLE 1. Code, sampling localities, haplotypes and accession numbers of Microphysogobio species and outgroup for molecular analysis; the haplotype with * means downloaded from GenBank.

Code	Species	Locality	Drainage	Haplotype	Accession no.	Source
ASIZB 220619	Microphysogobio bicolor	Yanshan County, Jiangxi Province	R. Xinjiang, Yangtze River Basin	H1	-------	This Study
ASIZB 220620	Microphysogobio bicolor	Yanshan County, Jiangxi Province	R. Xinjiang, Yangtze River Basin	H2	-------	This Study
ASIZB 220621	Microphysogobio bicolor	Yanshan County, Jiangxi Province	R. Xinjiang, Yangtze River Basin	H3	-------	This Study
ASIZB 220622	Microphysogobio bicolor	Yanshan County, Jiangxi Province	R. Xinjiang, Yangtze River Basin	H4	-------	This Study
ASIZB 220629	Microphysogobio bicolor	Wuyuan County, Jiangxi Province	R. Raohe, Yangtze River Basin	H5	-------	This Study
ASIZB 220630	Microphysogobio bicolor	Wuyuan County, Jiangxi Province	R. Raohe, Yangtze River Basin	H6	-------	This Study
ASIZB 220646	Microphysogobio bicolor	Wuyuan County, Jiangxi Province	R. Raohe, Yangtze River Basin	H7	-------	This Study
ASIZB 220647	Microphysogobio bicolor	Wuyuan County, Jiangxi Province	R. Raohe, Yangtze River Basin	H8	-------	This Study
ASIZB 220648	Microphysogobio bicolor	Wuyuan County, Jiangxi Province	R. Raohe, Yangtze River Basin	H8	-------	This Study
ASIZB 220649	Microphysogobio bicolor	Wuyuan County, Jiangxi Province	R. Raohe, Yangtze River Basin	H8	-------	This Study
ASIZB 220682	Microphysogobio zhangi	Yanshan County, Jiangxi Province	R. Xinjiang, Yangtze River Basin	H1	-------	This Study
ASIZB 220683	Microphysogobio zhangi	Yanshan County, Jiangxi Province	R. Xinjiang, Yangtze River Basin	H2	-------	This Study
ASIZB 220684	Microphysogobio zhangi	Yanshan County, Jiangxi Province	R. Xinjiang, Yangtze River Basin	H3	-------	This Study
ASIZB 220715	Microphysogobio zhangi	Wuyuan County, Jiangxi Province	R. Xinjiang, Yangtze River Basin	H3	-------	This Study
ASIZB 220716	Microphysogobio zhangi	Wuyuan County, Jiangxi Province	R. Xinjiang, Yangtze River Basin	H4	-------	This Study
MZHGL1	Microphysogobio zhangi	Guilin City, Guangxi Zhuang Autonomous Region	R. Lijiang, Pearl River Basin	H5*	KU356194	Huang et al ., 2017
MZHGL2	Microphysogobio zhangi	Guilin City, Guangxi Zhuang Autonomous Region	R. Lijiang, Pearl River Basin	H6*	KU356195	Huang et al ., 2017
MZHQZ1	Microphysogobio zhangi	Quanzhou County, Guangxi Zhuang Autonomous Region	R. Xiangjiang, Yangtze River Basin	H7*	KU356196	Huang et al ., 2017
MZHQZ2	Microphysogobio zhangi	Quanzhou County, Guangxi Zhuang Autonomous Region	R. Xiangjiang, Yangtze River Basin	H8*	KU356197	Huang et al ., 2017
MZHQZ3	Microphysogobio zhangi	Quanzhou County, Guangxi Zhuang Autonomous Region	R. Xiangjiang, Yangtze River Basin	H9*	KU356198	Huang et al ., 2017
ASIZB 220771	Microphysogobio fukiensis	Guangze County, Fujian Province	R. Futunxi, Minjiang River Basin	H1	-------	This Study
ASIZB 220772	Microphysogobio fukiensis	Guangze County, Fujian Province	R. Futunxi, Minjiang River Basin	H2	-------	This Study
ASIZB 220802	Microphysogobio fukiensis	Wuyishan City, Fujian Province	R. Jianxi, Minjiang River Basin	H1	-------	This Study

......continued on the next page TABLE 1. (Continued)

Code	Species	Locality	Drainage	Haplotype	Accession no.	Source
ASIZB 220803	Microphysogobio fukiensis	Wuyishan City, Fujian Province	R. Jianxi, Minjiang River Basin	H1	-------	This Study
MFUMJ1	Microphysogobio fukiensis	Shaowu City, Fujian Province	R. Futunxi, Minjiang River Basin	H3*	KM999927	Huang et al ., 2016
MFUMJ3	Microphysogobio fukiensis	Xinquan Town, Fujian Province	R. Tingjiang, Hanjiang River Basin	H4*	KM999929	Huang et al ., 2016
MELQZ1	Microphysogobio elongatus	Quanzhou County, Guangxi Zhuang Autonomous Region	R. Xiangjiang, Yangtze River Basin	H1*	KU356199	Huang et al ., 2017
MBRKL1	Microphysogobio brevirostris	Keelung City, Taiwan Province	R. Keelung, Tamsui River Basin	H1*	KM999926	Huang et al ., 2016
MXIML1	Microphysogobio xianyouensis	Xianyou County, Fujian Province	Mulanxi River Basin	H1*	KM999931	Huang et al ., 2016
MALKP1	Microphysogobio alticorpus	Pingtung County, Taiwan Province	Kaoping River Basin	H1*	KM999925	Huang et al ., 2016
MKAND1	Microphysogobio kachekensis	Nankai Town, Hainan Province	Nandujiang River Baisn	H1*	KM999930	Huang et al ., 2016
MYUVN1	Microphysogobio yunnanensis	Dien Bien, Vietamn	R. Lixianjiang, Red River Basin	H1*	MK133329	Huang et al ., 2018
MLURJ1	Microphysogobio luhensis	Luhe County, Guangdong Province	Rongjiang River Basin	H1*	KT877355	Huang et al ., 2018
OutGroup
Unknown	Saurogobio dabryi	Unknown	Yangtze River Basin	H1*	AY953011	Huang et al ., 2017
PVAHJ1	Pseudogobio vaillanti	Changting County, Fujian Province	Hanjiang River Basin	H1*	KM999932	Yang et al . 2006

Material examined. ASIZB 220619-27 , 9 specimens , 39.1–50.3 mm SL; China : Jiangxi Province : Yanshan County : Yongping Town : Yanshanhe River ( 28°13'10.09"N , 117°47'7.25"E , near the type locality), Yangtze River Basin ; collected by Zhi-Xian Sun and Rui Zhang , 11–12 April 2021 ; ASIZB 220628-35 , 8 specimens , 42.1–62.2 mm SL; China : Jiangxi Province : Wuyuan County : Taibai Town : Le’anhe River ( 29°4'29.21"N , 117°40'3.98"E ), Yangtze River Basin ; collected by Zhi-Xian Sun , 16 December 2020 ; ASIZB 220636-40 , 5 specimens , 65.5–84.5 mm SL; China : Jiangxi Province : Wuyuan County : bought from Dongmen-Market , Le’anhe River , Yangtze River Basin ; collected by Zhi-Xian Sun , 11 April 2021 . Diagnosis. The species is distinguished from congeners by a combination of the following characteristics: mouth horseshoe-shaped and inferior; central portion of anterior papillae arranged in one row, tightly contact with each other, equal or slightly larger than all others papillae which on upper lip, width 26.3–37.3% of mouth width; lateral-line scales 36–38; branched anal-fin rays 5; midventral region of body scaleless before pectoral-fin base end; posterior chamber of air-bladder length equal to eye diameter; vertebrae 4+32; body usually sharply bicolored. Description. Body elongated, lower surface of head and breast flattened, abdomen rounded, caudal peduncle short, slightly compressed. Dorsal body profile rising smoothly from nostrils to dorsal-fin origin, gradually sloping along dorsal-fin base, then sloping smoothly to caudal-fin base. Maximum body depth at dorsal-fin origin, body depth 15.7–24.3% of standard length. Head length, slightly greater than body depth (102.2–151.4% of head length); snout bluntly pointed, with a shallow concavity on the top of snout before nostrils; eye large, 26.0–33.9% of head length, placed in dorsal half of head; nostrils positioned close together, in front of eyes; interorbital region slightly concave, width smaller than eye diameter (58.4–86.8% of eye diameter). Anus positioned at anterior one-third of distance from pelvic-fin insertion to anal-fin origin. Mouth horseshoe-shaped and inferior, with a pair of barbels at extremity of mouth, barbel length approximately equal to half eye diameter (60.4% of eye diameter in average); upper and lower jaws with thin horny sheaths on cutting margins, width of cutting edge on upper jaw shorter than half mouth width (33.9% of mouth width in average). Lips thick, well developed, with pearl-liked papillae; central portion of anterior papillae arranged in one row, tightly contact with each other, equal or slightly larger than all others papillae which on upper lip, lateral portions of anterior papillae in several rows; medial pad on lower lip heart-shaped, completely divided, usually grooved; lateral lobes covered with about 40–60 small papillae in all, posteriorly disconnected from each other behind medial pad and laterally connected with upper lip around corners of mouth ( Fig. 3A, B ). Body covered with moderately small cycloid scales. Lateral line complete, almost straight in center, slightly bent down under dorsal origin. Lateral line scales 36 ( 2 specimens ), 37 (14), 38 (6); scales above lateral line 3.5 (22); scales below lateral line 2 (22); pre-dorsal scales 9 (7), 10 (15); circumpeduncular scales 12 (22). Midventral region of body scaleless before pectoral-fin base end ( Fig. 3B ). Dorsal fin with 3 unbranched and 7 ( 22 specimens ) branched rays; distal margin concave, origin nearer to snout than caudal-fin base. Pectoral fin with 1 unbranched and 11 (4), 12 (18) branched rays; tip of adpressed not reaching anterior margin of pelvic-fin base. Pelvic fin with 1 unbranched and 7 (22) branched rays, inserted below third or fourth branched dorsal-fin ray; tip of adpressed reaching midway to anal-fin origin. Anal fin with 3 unbranched and 5 (22) branched rays; origin almost equidistant between pelvic-fin insertion and caudal-fin base. Caudal fin deeply forked, with 9 branched rays on upper lobes and 8 branched rays on lower lobes, lobes pointed. FIGURE 1. Microphysogobio bicolor , holotype, AMNH 9678, 59.8 mm SL; photographed by Dr. Thomas Vigliotta. Total vertebrae 4+32 (1, holotype ). Gill rakers rudimentary. Pharyngeal teeth “5–5” (in one row). Air-bladder small sized, the anterior chamber enveloped in a thick fibrous capsule; the posterior chamber developed, connected with anterior chamber, oval shaped, length equal to eye diameter. FIGURE 2. Microphysogobio bicolor , ASIZB 220626, 50.3 mm SL. A. lateral view; B. ventral view; C. dorsal view. Coloration in life. Usually sharply bicolored ( Fig. 4 ). Dorsal side of head and body deep yellowish brown, midlateral side yellowish brown, and ventral side grayish white. Dorsal side of body with five distinct black crossbars (first on back of head, vague and small, second and third at dorsal-fin base origin and ending respectively, fourth at vertical position above anal-fin base origin, fifth on caudal peduncle respectively). One black strip on lateral line scales with 7–8 vague black blotches; scales above lateral line black spotted, lateral line scales and first line of scales below lateral line black margined. Interorbital region without black crossbar. Operculum and suborbital region with three distinct black blotches (first between anterior margin of eye and upper lip, second on suborbital plate but narrow and vague, third on cheek and lower opercle significantly). One black blotch above pectoral-fin base. Fins translucent, with black pigments on some fin rays; dorsal-fin rays with some black spots; pectoral fin, pelvic fin with tiny black spots and lines; anal fin without spots; caudal-fin rays with many black spots. FIGURE 3. Lip papillae system. A. Microphysogobio bicolor , ASIZB 220626, 50.3 mm SL; B. Microphysogobio bicolor , ASIZB 220638, 76.9 mm SL; C. Microphysogobio fukiensis , ASIZB 220659, 54.9 mm SL; D. Microphysogobio zhangi , ASIZB 220677, 60.7 mm SL; E. Microphysogobio kachekensis , ASIZB 69768, 100.0 mm SL; F. Microphysogobio luhensis , ASIZB 204717, holotype, 55.5 mm SL. FIGURE 4. Live Microphysogobio bicolor freshly collected near its type locality. Coloration in preservative. Specimen bicolored, dorsal and mid-lateral side of head and body grayish brown, ventral side grayish yellow. Dorsal side of body with five distinct black crossbars in same position as living specimen, last three crossbars significantly distinct. One deep grayish blue strip on lateral line scales with 7–8 vague deep grayish blue blotches; scales above lateral line black spotted, lateral line scales and first line of scales below lateral line deep gray margined. Interorbital region without black crossbar. Operculum and suborbital region with three distinct deep grayish blue blotches, same position as living specimen. One gray blotch above pectoral-fin base. All fins yellow, with brown pigments on fin rays; all spots and lines same position as living specimen. Sexual dimorphism. In the breeding season, adult males possess numerous tiny bead pearls on the tip of snout, anterior of the eyes, ventral side of the head, and on the unbranched pectoral-fin rays ( Fig. 5 ). FIGURE 5. Pearl organs of an adult male Microphysogobio bicolor . Distribution. According to the original description and previous collections, Microphysogobio bicolor is distributed in Xinjiang River and Raohe River, the two rivers flow into the Poyang Lake, which belong to the middle Yangtze River Basin, located in Jiangxi Province ( Fig. 6 ). FIGURE 6. Distribution of Microphysogobio bicolor , M. fukiensis and M. zhangi . Habitat and biology. Microphysogobio bicolor inhabits the flowing water of rivers. It usually appears in areas with sandy bottoms with gravel and pebbles ( Fig. 7 ). Coexisting species at its type locality included Pseudohemiculter hainanensis , Opsariichthys acutipinnis , Rhodeus ocellatus , Squalidus wolterstorffi , Squalidus argentatus , Sarcocheilichthys parvus , Microphysogobio zhangi , Vanmanenia maculata , Tachysurus ondon and Tachysurus aff. gracilis . Etymology. The name, bicolor , was derived from the sharp bicolored specimen Nichols (1930) described which dark above and pale below. Chinese common name for this species is “ uffl小üḃ ”. Genetic comparisons. A total of 28 haplotypes from 33 Microphysogobio individuals for Cyt b gene were included in this analysis. The molecular phylogenetic results based on mitochondrial Cyt b sequence shows that Microphysogobio bicolor forms a monophyletic clade itself, which is sister to the M. luhensis – M. kachekensis – M. yunnanensis clade ( Huang et al. , 2018 ). Microphysogobio fukiensis and M. zhangi each represent a clade which are sister to each other. The interspecific genetic distances between M. bicolor and three congeners M. kachekensis , M. luhensis and M. yunnanensis are 10.1%, 10.2% and 10.1%, respectively, for Cyt b based on the K2P model. The interspecific genetic distances between M. bicolor and M. fukiensis and M. zhangi are 12.9% and 13.7% for Cyt b based on the K2P model. The intraspecific genetic distances in M. bicolor , M. fukiensis and M. zhangi are 1.0%, 0.3% and 2.5%, respectively, which are much lower than the inter-species genetic distances. The genetic evidence strongly supported M. bicolor to be a distinct species. The phylogenetic trees reconstructed by the BI and ML methods showed the same tree topology and the value of each methods are shown in the tree ( Fig. 8 ). The genetic distances of the Cyt b gene amongst 10 species of Microphysogobio are given in Table 2 .