Cobitis minamorii Nakajima, 2012

Nakajima, Jun, 2012, Taxonomic study of the Cobitis striata complex (Cypriniformes, Cobitidae) in Japan, Zootaxa 3586, pp. 103-130 : 119-121

Cobitis minamorii Nakajima , sp. nov.

( Figs. 3F, 5F, 6F, 8A, B)

Cobitis taenia striata small race: Minamori 1952: 201, fig. 2B; Cobitis taenia striata small race: Saitoh and Aizawa 1987: 336, fig. 3D; Cobitis sp. S (Sanyo-gata): Saitoh 1989: 388; small form: Saitoh 1990: 240, figs. 3a, b, c, d, e: 241, fig. 4 (upper four); Cobitis sp. 2 subsp. 1: Hosoya 2002: 275; Cobitis striata complex small race, Sanyo form: Kitagawa et al. 2005: 112, table 1; Cobitis striata complex small race: Saitoh et al. 2010: 1003, table 1; Cobitis sp. 2 subsp. 1: Nakajima et al. 2012: 90, fig. 2b.

Holotype. TKPM-P17345 , 1 male, 48.9 mm SL, Japan: Kagato River, Yoshii River system, Setouchi , Okayama Pref., Honshu , 6. VI. 2007, J. Nakajima.

Paratypes. KPM-NI29507 , 1 male, 42.0 mm SL, same data as holotype; MPM-FI1505, 1 male, 37.2 mm SL, same data as holotype ; KPM-NI9225 , female, 33.4 mm SL, Asahi R., Okayama, Okayama Pref., Honshu, 31. VII. 1997 , T. Okazaki and M. Watanabe .

Non-type specimens. FAKU055761 , 3 males, 38.1–46.4 mm SL, Imizo R., Ashida R. s., Fukuyama , Hiroshima Pref., Honshu, 2. V. 1982, K. Saitoh ; FAKU055675 , 3 males, 40.1–47.6 mm SL, Omachi R., Asahi R. s., Okayama, Okayama Pref., Honshu , 23. IV. 1981, K. Saitoh; 2 males and 7 females, 40.0– 55.5 mm SL, same data as holotype .

Diagnosis. This species is distinguishable from other Japanese striated spined loaches by the following characteristics: body size small, the mature size about 35–45 mm SL in males, 45–55 mm SL in females; lamina circularis at the base of the pectoral fin of adult male a roundish plate, somewhat narrowing toward the outer part; upper segments of the first branched soft ray of pectoral fin narrow and weak ( Fig. 6F); PMN commonly 12; snout short; eye diameter relatively large; body depth and caudal peduncle relatively deep; line L1 consisting of a series of 15–25 blotches; blotches saddle or oval-shaped; line L2 formed by longitudinal jagged line or angular blotches, reaching to pre- or middorsal region, often fused with L1; line L3 formed by incomplete longitudinal narrow line, reaching beyond dorsal fin; line L5 formed by narrow incomplete longitudinal line or organized in chained tiny 15–20 blotches; caudal and dorsal fin with 3–4 irregular vertical bars and exterior bar weak margined; upper spot at the caudal base black, smaller than eye diameter; lower spot at caudal base existing but faint; each spots not connected; egg yolk diameter approximately 0.8 mm; karyotype diploid (2n = 49 in male, 50 in female).

Description. Lateral view in Figure 3F illustrate body shape, form and position of fins. Morphometric and meristic data for 11 males and 7 females are summarized in Table 2. Dorsal-fin rays iii, 7; anal-fin rays iii, 5; pectoral-fin rays i, 7–8; pelvic-fin rays ii, 6; caudal-fin rays 8+8. Body some what waistless, laterally compressed. Snout short comparatively. Interorbital space broad, convex. Eye diameter relatively large. Body depth and caudal peduncle relatively deep. 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, 11–14). 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. 6F). 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: 48.9 mm SL male, 55.5 mm SL female.

Coloration. Male in the non-spawning season ( Figs. 3F, 8A). Body pearl white with dark brown pigmentation in fresh specimens. Clear streak running from the tip of snout to the occiput, crossing to the eye. Upper part of head covered with 3–5 roundish. Opercle and snout covered with oval and amorphous shaped spots. Body pigmentation organized in one middorsal and four lateral zones. Line L1 consisting of a series of 15–25 blotches; blotches saddle or oval-shaped. Line L2 formed by longitudinal jagged line or angular blotches, reaching to pre- or middorsal region, often fused with L1. Line L3 formed by incomplete longitudinal narrow line, reaching to beyond dorsal fin, fused with L1 and L4 on posterior part. Line L4 formed by tiny blotches or narrow longitudinal line, reaching to dorsal fin. Line L5 formed by narrow incomplete longitudinal line or organized in chained tiny 15–20 blotches from upper part of the pectoral fin to the caudal-fin base. Caudal fin and dorsal fin with 3–4 irregular vertical bars and exterior bar often margined. Anal fin pigmented along the fin rays. Upper spot at the caudal base black, smaller than eye diameter, lower spot at caudal base faint; spots not connected.

Male in the spawning season ( Fig. 8B). Line L4 not visible or formed by narrow longitudinal line, present only in anterior half of body. Lines L3 and L5 well developed with narrow stripes from upper part of the pectoral-fin base to the caudal-fin base; the posterior part often intermissive.

Female ( Fig. 5F). 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. 0.85 ± 0.04 mm (females, N = 3; collected from the Yoshii River system, Okayama Prefecture).

Karyotype. Diploid (2n = 49 in male, 2n = 50 in female) (Saitoh et al. 1984, 2000).

Distribution. Rivers flowing into Seto Inland Sea, Sanyo district, western Honshu: Okayama and Hiroshima Prefectures ( Saitoh & Aizawa 1987).

Habitat and biology. This species inhabits sandy-mud bottoms of the lower reach of rivers and small stream. Saitoh (1990) described the spawning ecology of this species as small form of C. striata .

Etymology. The specific name is dedicated to Dr. Sumio Minamori who was the pioneer of the study of speciation of loaches in Japan.

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

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