Microphysogobio bicolor ( Nichols, 1930 )

Sun, Zhixian & Zhao, Yahui, 2022, Revalidation and redescription of a gobionine species Microphysogobio bicolor (Nichols, 1930) (Teleostei: Cypriniformes) from the Yangtze River Basin, China, Zootaxa 5092 (3), pp. 361-377 : 362-369

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.

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.

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.

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.

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 ).

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 ).

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 .

Figures

FIGURE 1. Microphysogobio bicolor, holotype, AMNH 9678, 59.8 mm SL; photographed by Dr. Thomas Vigliotta.

FIGURE 2. Microphysogobio bicolor, ASIZB 220626, 50.3 mm SL. A. lateral view; B. ventral view; C. dorsal view.

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.

FIGURE 5. Pearl organs of an adult male Microphysogobio bicolor.

FIGURE 6. Distribution of Microphysogobio bicolor, M. fukiensis and M. zhangi.

FIGURE 7. Habitat of Microphysogobio bicolor, China: Jiangxi Province: Shangrao City: Yanshan County: Yanshanhe River, Yangtze River Basin; 12 April 2021; photograph by Zhixian Sun.

FIGURE 8. Molecular phylogenetic tree of Microphysogobio bicolor and its congeners based on Cyt b sequence reconstructed by Bayesian Inference method (values above the branch) and maximum likelihood method (values below the branch).