Cobitis minamorii oumiensis Nakajima, 2012

Nakajima, Jun, 2012, Taxonomic study of the Cobitis striata complex (Cypriniformes, Cobitidae) in Japan, Zootaxa 3586, pp. 103-130 : 121-123

Cobitis minamorii oumiensis Nakajima , subsp. nov.

( Figs. 3G, 5G, 6G, 8C, D)

Cobitis taenia striata Biwa-small race: Minamori 1956: 91, fig. 1; Cobitis taenia striata Biwa small race: Saitoh and Aizawa 1987: 336, fig. 3B; Cobitis sp. S (Biwako-gata): Saitoh 1989: 387; Cobitis sp. S: Saitoh and Matsuda 1990: 19, fig. 1; Cobitis sp. 2 subsp. 4: Hosoya 2002: 276; Cobitis striata complex small race, Biwa form: Kitagawa et al. 2005: 112, table 1; Cobitis striata complex Biwa small race: Saitoh et al. 2010: 1003, table 1; Cobitis sp. 2 subsp. 4: Nakajima et al. 2012: 90, fig. 2e.

Holotype. TKPM-P17346 , 1 male, 51.7 mm SL, Japan: small stream flowing into Biwa Lake, Takashima, Shiga Pref., Honshu , 24. V. 2007, S. Yodo.

Paratypes. JNC037, 1 male, 48.2 mm SL, small stream flowing into Biwa Lake, Takashima, Shiga Pref., Honshu , 15. V. 2009, J. Nakajima; KPM-NI29508 , 1 male, 48.9 mm SL, same data as holotype ; MPM-FI1506, 1 male, 48.6 mm SL, same data as holotype ; KPM-NI8989 , 1 female, 69.3 mm SL, Imazu, Takashima, Shiga Pref., Honshu , 19. V. 2000, T. Satou .

Non-type specimens. FAKU55876 , 5 males, 45.2–53.2 mm SL, Takashima, Shiga Pref., Honshu , 6. VI. 1983, K. Saitoh; 2 males and 3 females, 44.4–68.7 mm SL, same data as holotype; 2 females, 63.4, 74,5 mm SL, small stream flowing into Biwa Lake, Takashima, Shiga Pref., Honshu , 15. V. 2009, J. Nakajima.

Diagnosis. This subspecies is distinguishable from other Japanese striated spined loaches by the following characteristics: body size small, the mature size about 45–55 mm SL in males, 50–60 mm SL in females; lamina circularis at the base of the pectoral fin of adult male roundish plate, somewhat narrowing toward the outer part; upper segments of the first branched soft ray of pectoral fin narrow and weak ( Fig. 6G); PMN commonly 12; snout short; line L1 consisting of a series of 14–16 blotches; blotches oval-shaped, often chainlike longitudinal jagged line; line L2 lacking; line L3 formed by sharp longitudinal line, reaching beyond dorsal fin; line L4 lacking or formed by weak dotted line; line L5 well developed with broad stripe in all season; caudal and dorsal fins margined by a broad black band; Upper and lower spot at caudal base black, upper sharpen, lower somewhat pale; spots slightly connected; egg yolk diameter approximately 0.8 mm; karyotype diploid (2n = 50).

Description. Lateral view in Figure 3G illustrate body shape, form and position of fins. Morphometric and meristic data for 11 males and 5 females are summarized in Table 2. Dorsal-fin rays iii, 7; anal-fin rays iii, 5; pectoral-fin rays i, 7; pelvic-fin rays ii, 5–6; caudal-fin rays 8+8. Body elongate, laterally compressed. Snout short comparatively. Interorbital space narrow, convex. Caudal peduncle relatively compressed. Mouth small, inferior, arched with fleshy lips; lower lip divided with two well-developed lobes; upper lip with transverse wrinkles on surface. Barbels, 3 pairs, first on rostora, second on maxillae, third on maxillomandibula; each barbel well developed, length of maxillary barbel same as eye diameter; length of rostral and mandibular barbels shorter than that of maxillary barbel. Lateral line short, reaching the central region between the pectoral-fin base and the tip of the fin. PMN commonly 12 (range, 11–13). Very small cycloid scales on the trunk. Lamina circularis at the base of the pectoral fin of adult male roundish plate, somewhat narrowing toward the outer part ( Fig. 6G). The first branched soft ray of pectoral fin longer than the other rays; pectoral fin of the male relatively longer than that of the female. The upper segments of the first branched soft ray of pectoral fin narrow and weak. Dorsal-fin base equidistant from the base of the caudal fin and the tip of the snout. Pelvic-fin origin below first or second branched dorsal-fin ray. Anal fin not reaching caudal-fin base. Margin of anal and dorsal fins slightly roundish. Caudal fin slightly roundish. Largest recorded specimens: 53.2 mm SL male, 74.5 mm SL female.

Coloration. Male in the non-spawning season ( Figs. 3G, 8C). Body pearl white with black pigmentation in fresh specimens. Clear streak running from the tip of snout to the occiput, crossing to the eye. Head, opercle and snout covered with some large amorphous patterns. Line L1 consisting of a series of 14–16 blotches; blotches ovalshaped, often chainlike longitudinal jagged line. Line L2 lacking. Line L3 formed by sharp longitudinal line, reaching beyond dorsal fin. Line L4 lacking or formed by weak dotted line, present only in anterior half of body. Line L5 well developed with broad stripe from upper part of the pectoral fin to the caudal-fin base. Caudal fin and dorsal fin margined by a broad black band; various cloudy blotches or broken marks on other regions. Anal fin pigmented along the fin rays. Upper and lower spot at caudal base black, upper sharpen, lower somewhat pale; spots slightly connected.

Male in the spawning season ( Fig. 8D). Line L3 well developed with broad stripe from upper part of the pectoral-fin base to the posterior part of the dorsal fin. Line L5 well developed with broad stripe from upper part of the pectoral-fin base to the caudal-fin base. Lines L2 and L4 lacking.

Female ( Fig. 5G). Appearance similar to males in the non-spawning season.

Sexual dimorphism. Males have roundish lamina circularis at the base of the pectoral fin, but females do not. Generally, the body size of females is larger than that of males.

Egg diameter. 0.84 ± 0.03 mm (females, N = 2; collected from small stream flowing into the Biwa Lake, Shiga Prefecure).

Karyotype. Diploid (2n = 50) ( Ueno & Ojima 1976; Ueno et al. 1980; Ueno 1981; Kimizuka 1987; Saitoh et al. 2000).

Distribution. Lake Biwa, central Honshu: Shiga Prefecture ( Saitoh & Aizawa 1987).

Habitat and biology. This subspecies inhabits sandy-mud bottoms of small streams, and spawns in paddy field ( Saitoh & Matsuda 1990).

Etymology. The subspecific name is derived from Oumi, the old name of Lake Biwa, the type locality.

Remarks. The genetic features have been reported by Kitagawa et al. (2005) and Saitoh et al. (2010).

Japanese name. Biwa-kogata-suji-shima-dojyô.