Cobitis kaibarai Nakajima, 2012

Nakajima, Jun, 2012, Taxonomic study of the Cobitis striata complex (Cypriniformes, Cobitidae) in Japan, Zootaxa 3586, pp. 103-130 : 116-118

Cobitis kaibarai Nakajima , sp. nov.

( Figs. 3D, 5D, 6D, 7A, B)

Cobitis sp. S Kyushu-gata: Saitoh 1989: 389; Cobitis sp. 2 subsp. 3: Hosoya 2002: 275; Cobitis striata complex Small race, Kyushu form: Kitagawa et al. 2005: 112, table 1; Kyushu form of Cobitis striata (small race): Nakajima et al. 2008: 13, fig. 2D; Cobitis striata complex Kyushu form: Saitoh et al. 2010; 1003, table 1; Cobitis sp. 4 : Nakajima et al. 2012: 92, fig. 3d.

Holotype. TKPM-P17343 , 1 male, 54.5 mm SL, Japan: Mitsuru River, Chikugo River system, Ukiha , Fukuoka Pref., Kyushu , 15. XII. 2010, J. Nakajima.

Paratypes. MPM-FI1503, 1 male, 52.3 mm SL, creek of Kikuchi R. s., Tamana, Kumamoto Pref., Kyushu , 19. III. 2008, J. Nakajima; JNC015, 1 male, 47.2 mm SL, same data; JNC016, 1, male, 44.4 mm SL, same data; KPM- NI29505 , 1 male, 48.3 mm SL, creek of Rokkaku R. s., Taku, Saga Pref., Kyushu, 22. XII. 2010, E. J. Kim; JNC018, 1 male, 46.9 mm SL, same data; KPM-NI9231 , 1 female, 47.4 mm SL, Sakai R., Tamana, Kumamoto Pref., Kyushu, 24. XII. 1997, M. Watanabe .

Non-type specimens. 2 males and 2 females, 49.4–56.1 mm SL, creek of Kikuchi R. s., Tamana, Kumamoto Pref., Kyushu , 4. VI. 2007, J. Nakajima ; 2 males, 51.9, 52.3 mm SL, Kose R., Chikugo R. s., Ukiha , Fukuoka Pref., Kyushu , 14. VIII. 2007, J. Nakajima ; 1 female, 63.9 mm SL, same data ; 1 male and 1 female, 47.9, 68.1 mm SL, creek of Kase R. s., Saga, Saga Pref., Kyushu , 16. V. 2008, J. Nakajima ; 1 male and 1 female, 50.1, 65.8 mm SL, creek of Rokkaku R. s., Taku , Saga Pref., 23. XI. 2010, Y. Suzawa ; 1 female, 56.7 mm SL, creek of Rokkaku R. s., Taku, Saga Pref., Kyushu , 22. XII. 2010, E. J. Kim .

Diagnosis. This species is distinguishable from other Japanese striated spined loaches by the following characteristics: body size relatively small, the mature size about 45–55 mm SL in males, 55–65 mm SL in females; lamina circularis at the base of the pectoral fin of adult male simple roundish plate, the upper segments of the first branched soft ray narrow and weak ( Fig. 6D); PMN commonly 13; line L3 formed by incomplete longitudinal line, reaching to caudal base, fused with L1 and L4 on posterior part of body; line L4 formed by longitudinal jagged line, reaching beyond dorsal fin in male of non-spawning season; line L5 organized in 10–16 roundish or ovoid blotches, fused with L4 on caudal body in non-spawning season; caudal fin and dorsal fin with 4–5 arcuate bars; upper spot at the caudal base jet-black approximately eye diameter; lower spot at caudal base faint or missing; egg yolk diameter approximately 0.8 mm; karyotype diploid (2n = 50).

Description. Lateral view in Figure 3D illustrate body shape, form and position of fins. Morphometric and meristic data for 12 males and 6 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. Head and snout elongated. 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 13 (range, 13–14). Very small cycloid scales on the trunk. Lamina circularis at the base of the pectoral fin of adult male simple roundish plate ( Fig. 6D). 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: 54.5 mm SL male, 68.1 mm SL female.

Coloration. Male in the non-spawning season ( Figs. 3A, 7A). Body yellowish white with brown pigmentation in fresh specimens. Clear streak running from the tip of snout to the occiput, crossing to the eye. Upper part of head, opercle and snout covered with oval or amorphous shaped spots. Body pigmentation organized in one middorsal and four lateral zones. Line L1 consisting of a series of 12–25 blotches; blotches saddle or oval-shaped. Line L2 formed by longitudinal jagged line or small angular blotches, reaching to postdorsal region, often fused with L1. Line L3 formed by incomplete longitudinal line, reaching to caudal base, fused with L1 and L 4 in postdorsal region. Line L4 formed by longitudinal jagged line, reaching beyond dosal fin, width variable. Line L5 organized in 10–16 blotches from upper part of the pectoral fin to the caudal-fin base; blotches roundish or ovoid, fused with L4 on caudal body. Caudal fin and dorsal fin with 4–5 arcuate bars. Anal fin pigmented along the fin rays. Upper spot at the caudal base jet-black comparable in size to eye diameter, lower spot at caudal base faint or missing.

Male in the spawning season ( Fig. 7B). Line L4 not visible or formed by narrow longitudinal line, present only in anterior half of body. Lines L3 and L5 well developed with broad stripes from upper part of the pectoral-fin base to the caudal-fin base.

Female ( Fig. 5D). 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. 0.83 ± 0.04 mm (females, N = 2; collected from the Kikuchi River system, Kumamoto Prefecture).

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

Distribution. Rivers flowing into Ariake estuary, northern Kyushu: Saga, Fukuoka, and Kumamoto Prefectures ( Nakajima et al. 2008).

Habitat and biology. This species inhabits sandy-mud bottoms of the middle and lower reaches of rivers and small streams. Life histories are unknown.

Etymology. The specific name is dedicated to the late Mr. Ekiken Kaibara who was the first real naturalist and biologist in Japan. He recorded the distribution of spined loaches from Chikushi (modern-day Fukuoka Prefecture), Kyushu Island for the first time ( Kaibara 1709).

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

Japanese name. Ariake-suji-shima-dojyô.