著者

岡田 彌一郎 池田 兵司

出版者

社団法人日本動物学会

雑誌

動物学雑誌 (ISSN:00445118)

巻号頁・発行日

vol.49, no.5, pp.161-172, 1937-05-15

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The present paper is concerned with statistical observations on the species of the Genus Tribolodon of Hokkaido, Japan and with some notes on their distribution. In regions adjacent to Hokkaido some species of the present genus have been known, but from Hokkaido only one species, Tribolodon hakuensis (GUNTHER), has been reported. During the summers of 1930 to 1936, the senior author visited Hokkaido and obtained the precious collections, which contain 424 specimens of the present genus, from the rivers and lakes of this region. According to our observations on these collections, we suggest that the present genus in Hokkaido may include the following four species. 1. Tribolodon hakuensis hakuensis (GUNTHER) This species represents Leuciscus hakuensis GUNTHER proper and has 66-80 scales in the lateral line and below 35-38 scales anterior to the dorsal fin. 2. Tribolodon hakuensis phalacrocorax (JORDAN and FOWLER) This species represents Leuciscus phalacrocorax JORDAN and FOWLER proper and has 60-70 scales in the lateral line and below 35-38 scales before the dorsal fin. On account of the characteristic difference in the number of scales in the lateral line, which is proposed by JORDAN and HUBBS, we are able to distinguish the present species from the above-mentioned T. hakuensis hakuensis, but the number of scales in these two species intergradates with each other. Considering the correlation between the number of scales in the lateral line and the scales anterior to the dorsal fin, the length of the body and the snout, it seems to be desirable to recognize the present species not as a distinct species but as a subspecies of Tribolodon hakuensis. 3. Tribolodon hakuensis ezoe subsp. nov. The present subspecies resembles the above-mentioned T. hakuensis hakuensis, but differs from it in having above 35-38 scales before the dorsal fin and 15-16 scales above the lateral line, also the length of the head and the snout greater. 4. Tribolodon jusanensis (JORDAN and HUBBS) This species represents Acahara jusanensis JORDAN and HUBBS and has 80-98 scales in the lateral line, 38-50 scales anterior to the dorsal fin and 16-20 scales above the lateral line. The head and snout are long. In Leuciscus taczanowskii STEINDACHMER, JORDAN and HUBBS (1925) recognized two species, A. jusanensis and L. taczanowskii proper, the latter was regarded as being identical to Leuciscus brandti(DYBOWSKY) by BERG (1909). But, according to FOWLER's description (1924). L. taczanowskii is distinguished from L. brandti by having fewer scales anterior to the dorsal fin and no black blotch at the base of the caudal fin. It seems to be rather clearly related to A. jusanensis. T. hakuensis hakuensis and T. hakuensis ezoe are widely distributed in Hokkaido but other species are regional as follows: T. phalacrocorax, Lake Panke, Lake Akan; T. jusanensis, Lake Tofutsu, Lake Mokoto, Lake Abashiri.