Biwia Jordan & Fowler, 1903

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

Biwia Jordan & Fowler, 1903

Fig. 6

Biwia Jordan & Fowler, 1903: 838. Type species: Pseudogobio zezera Ishikawa, 1895.

Diagnosis.

The genus Biwia can be distinguished from the other genera within the Pseudogobionini by having no barbel.

Description.

Body elongated, rather rounded, laterally compressed, and somewhat broad forward. Mouth arc-shaped and inferior; no barbel; lips thin, smooth, no papillae; lower lip possessing two rounded fleshy protrusion, smooth, without papillae, forming the medial pad; lower lip connected with each other anterior from medial pad and laterally connected with upper lip around mouth corners (Fig. 3 A ). Body covered with moderately large cycloid scales. Thoracic region scaleless. Anus positioned in anterior one-third of pelvic-fin insertion and anal-fin base. Lateral line complete, almost straight. Lateral-line scales usually 34–38; scales above lateral line 4.5; scales below lateral line usually 3; predorsal scales 10–11; circumpeduncular scales 12. Dorsal fin with three or four unbranched and six or seven branched rays, pectoral fin with one unbranched and nine or ten branched rays, pelvic fin usually with one unbranched and seven or eight branched rays, anal fin with three unbranched and six branched rays; caudal fin forked, with one simple ray and eight or nine branched rays on upper lobe, and seven or eight branched rays and one simple ray on lower lobe, lobes pointed. Pharyngeal teeth “ 5–5 ” in one row. Air bladder slightly enlarged, possessing two chambers; anterior chamber flat rounded, enclosed in a thick fibrous capsule; posterior chamber enlarged, length larger than anterior chamber length, spherical-shaped. Intestine short, simple.

Distribution.

This genus distributed in northern Kyushu, Sanyo, the Yodo River Basin (including Lake Biwa), and the Nagoya Basin (Nobi Plain). This genus is endemic to Japan (Fig. 5 B ).

Etymology.

The generic name refers to Lake Biwa, where the type species Biwia zezera occurs. The generic name in Chinese is “ 琵琶湖鮈 ” 属, and the Chinese Pinyin name is “ Pí Pa Hú Jū ” Shǔ.

Species included.

Biwia zezera ( Ishikawa, 1895) (type species).

Biwia yodoensis Kawase & Hosoya, 2010 .

Remarks.

This genus is restricted to only two valid species, Biwia zezera and B. yodoensis . Biwia tama Oshima, 1957 , was described based on a single specimen collected from downstream of the Tama River in Denyenchofu, Japan. According to the original description ( Oshima 1957, Fig. 2 ), the holotype actually represents a Sarcocheilichthys species. Biwia springeri ( Bănărescu & Nalbant, 1973) , originally described as Abbottina springeri from Pusan, South Korea, does not have the characters of Biwia . Having one pair of barbels, an arc-shaped mouth, a wide horny-sheathed upper jaw, and a three-lobed lower lip, this species should be placed in Microphysogobio .

Figures

Figure 2. The phylogenetic relationship of seven genera within the Biwia – Microphysogobio complex. A. Bayesian inference (BI) tree, posterior probabilities shown at nodes; B. maximum likelihood (ML) tree, bootstrap values shown at nodes.

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 6. The general view of Biwia zezera, the type species of the genus Biwia, KUN-P 040282, male, 53.8 mm SL, collected from Lake Biwa, Moriyama, Shiga, Japan. A. Lateral view; B. Dorsal view; C. Ventral view. Scale bar: 10 mm. Photographed by Seigo Kawase.