Mesophysogobio, Sun & Tang & Zhao, 2025

Sun, Zhi-Xian, Tang, Wen-Qiao & Zhao, Ya-Hui, 2025, Generic revision on the Biwia – Microphysogobio complex (Cypriniformes, Gobionidae) with descriptions of three new genera, Zoosystematics and Evolution 101 (4), pp. 2013-2037 : 2013-2037

Mesophysogobio gen. nov.

Fig. 9

Type species.

Pseudogobio kachekensis Oshima, 1926 .

Diagnosis.

The new genus can be distinguished from all other genera within the Pseudogobionini by the combination of the following characters: (1) mouth horseshoe-shaped and inferior; (2) central portion of the anterior papillae small and usually equal-sized, in tight contact with each other, in one row; (3) lower lip forming two lateral lobes and a medial pad, without anterior fold; (4) lateral lobes on lower lip not in contact with each other posteriorly from medial pad; (5) medial pad bisected, heart-shaped, with small papillae or shallow groove; (6) upper jaw narrow, the horny margin width less than half mouth width; (7) lower jaw not exposed, covered by medial pad; (8) barbel in one pair; (9) midventral region of body scaleless only before pectoral-fin base end; (10) pharyngeal teeth in one row; (11) anterior chamber of the air bladder enclosed in fibrous capsule; (12) posterior chamber relatively small, length larger than half or one eye diameter, equal to or slightly larger than anterior chamber length, oval-shaped.

Description.

Body elongated, abdomen rounded; caudal peduncle short, compressed laterally. Mouth horseshoe-shaped and inferior; barbel one pair; lips thick, with developed papillae; central portion of the anterior papillae small and usually equal-sized, in tight contact with each other, in one row, lateral portion of anterior papillae in several rows; lower lip forming two lateral lobes and one medial pad, without anterior fold; two lateral lobes on lower lip not in contact with each other posteriorly from medial pad, laterally connected with upper lip anterior papillae around mouth corners; medial pad bisected, heart-shaped, with small papillae or shallow groove. Jaws with horny sheathed edge; upper jaw narrow, horny margin width less than half mouth width; lower jaw not exposed, covered by medial pad (Fig. 3 E ). Body covered with moderately large cycloid scales. Thoracic region scaleless, mid-ventral region covered with scales. Anus positioned in anterior one-third of pelvic-fin insertion and anal-fin base. Lateral line complete, almost straight. Lateral-line scales usually 36–40; scales above lateral line 3.5–4.5; scales below lateral line usually 1.5–2; predorsal scales 8–11; circumpeduncular scales 12. Distal margin of expanded dorsal fin steep sloped, usually slightly concave, with three unbranched and seven branched rays, pectoral fin with one unbranched and 11–13 branched rays, pelvic fin usually with one unbranched and six or seven branched rays, anal fin with three unbranched and five or six branched rays; caudal fin forked, with one simple ray and nine branched rays on upper lobe and eight branched rays and one simple ray on lower lobe, lobes pointed. Pharyngeal teeth “ 5–5 ” in one row. Air bladder relatively small, possessing two chambers; anterior chamber rounded, enclosed in a thick fibrous capsule; posterior chamber relatively small, length larger than half or one eye diameter, equal to or slightly larger than anterior chamber length, oval-shaped. Intestine relatively long.

Distribution.

This genus is distributed in southern China, including the southern tributaries of the middle and lower Yangtze River, the Qiantangjiang River, the Pearl River, and the Yuanjiang River (Red River) basins, and also the coastal rivers along the southern coastline of mainland China and Hainan Island from the Rongjiang River to the Beilunhe River. It also occurs in the Red River Basin and upper reaches of the Xijiang River (the longest tributary of the Pearl River) in northern Vietnam and the upper reaches of the Ma River in Laos (Nam Mat and Nam Ma basins, Kottelat, 2001) (Fig. 5 H ).

Etymology.

The prefix “meso-” was derived from the Greek word “ mesos ”, meaning middle, being intermediate; “ physo- ”, from the Greek word “ physa ”, referring to the air bladder. The generic name refers to the medium-sized posterior chamber of the air bladder, which is shared by species within this genus when compared with the genus Microphysogobio . The suggested Chinese name for this genus is “ 中鳔鮈 ” 属, and the Chinese Pinyin name is “ Zhōng Biào Jū ” Shǔ.

Species included.

Mesophysogobio kachekensis (Oshima, 1926) , comb. nov. (type species).

Mesophysogobio bicolor (Nichols, 1930) , comb. nov.

Mesophysogobio yunnanensis (Yao & Yang, 1977) , comb. nov.

Mesophysogobio luhensis (Huang, Chen, Zhao & Shao, 2018) , comb. nov.

Mesophysogobio punctatus ( Sun, Tang & Zhao, 2024) , comb. nov.

Remarks.

Within the Biwia – Microphysogobio complex, the new genus Mesophysogobio can be distinguished from the genus Biwia by having barbels (vs. no barbels) and well-developed lip papillae (vs. thin and simple). It can be distinguished from the genera Microphysogobio and Huigobio by having a narrow upper jaw horny margin, less than half of the mouth width (vs. wide, larger than half of the mouth width), and a larger posterior chamber of the air bladder, with length usually equal to or slightly longer than the anterior chamber length (vs. tiny, shorter than the anterior chamber length). It can be distinguished from the genus Platysmacheilus by having a well-trilobed lower lip (vs. not lobed). It is also different from the new genus Crossocheilogobio by having a heart-shaped medial pad on the lower lip (vs. an elongated and narrow medial pad). It is morphologically most similar to the new genus Oriengobio in sharing a narrow horny margin on the upper jaw and a one-row central portion of the anterior papillae. However, it can still be distinguished from Oriengobio by having a larger posterior chamber, longer than the anterior chamber length (vs. tiny, shorter than the anterior chamber length), an equal-sized and tightly contacting central portion of the anterior papillae (vs. an enlarged and sometimes loosely arranged), and papillae or a groove-covered medial pad on the lower lip (vs. a smooth medial pad).

Figures

Figure 3. Lip papillae patterns of the type species of seven genera within the Biwia – Microphysogobio complex, with a diagrammatic illustration showing the structures. A. Biwia zezera, KUN-P 040282; B. Microphysogobio hsinglungshanensis, ASIZB 240788; C. Huigobio chenhsienensis, SHOU 20231209015; D. Oriengobio fukiensis, ASIZB 220659; E. Mesophysogobio kachekensis, ASIZB 69768; F. Platysmacheilus exiguus, ASIZB 220879; G. Crossocheilogobio tafangensis, ASIZB 60212; H. diagrammatic illustration based on Microphysogobio chinssuensis. CPAP = central portion of anterior papillae; LPAP = lateral portion of anterior papillae; MP = medial pad; LL = lateral lobe; BB = barbel; UJ = upper jaw; LJ = lower jaw. The photo of Biwia zezera is provided by Seigo Kawase; the other photos and illustration were made by Zhi-Xian Sun.

Figure 5. The distributions of the Biwia – Microphysogobio complex and seven genera. A. The complex; B. Biwia; C. Microphysogobio; D. Huigobio; E. Platysmacheilus; F. Crossocheilogobio gen. nov.; G. Oriengobio gen. nov.; H. Mesophysogobio gen. nov.

Figure 9. The general view of Mesophysogobio kachekensis, the type species of the genus Mesophysogobio gen. nov., ASIZB 69768, male, 93.2 mm SL, collected from a tributary of the Dasijiang River in the Maolingjiang River system, Shangsi County, Guangxi Zhuang Autonomous Region, China. A. Lateral view; B. Dorsal view; C. Ventral view. Scale bar: 10 mm. Photographed by Zhi-Xian Sun.