オイカワ, <I>Zacco platypus</I> (Temminck and Schlegel) の繁殖―I.臀鰭における性徴と成熟

• 水口 憲哉

  東京大学農学部水産学科

• 檜山 義夫

  東京大学農学部水産学科

書誌事項

タイトル別名

• Reproduction of the Oikawa, <I>Zacco platypus</I> (Temminck and Schlegel), a Cyprinid I. Sexual Characters in the Anal Fin and Maturation Kenya Mizuguchi and Yoshio Hiyama

抄録

The Oikawa, Zacco platypus, is the popular game fish which widely inhabits the rivers and ponds all through Japan except Hokkaido. Along with the study on the life-history, ecology and population of the species, which has been carried out since 1965 mainly in the water of the River Aki (a tributary of the River Tama flowing into Tokyo Bay), the authors have studied the relationships between the maturity and sexual characters in the anal fin. Based on the inspection of 1628 specimens collected monthly by a cast-net from November 1965 to September 1966 and in May 1967, and by angling in August 1966, the following results were obtained. 1) The males during the spawning season (June to August) were characterized by well-developed pearl organs, red and bluish green color on the side and enormously grown anal fin. These mature males, dominated by age group III⁺ and a half of males of age group II⁺, exhibited breeding reactions and died out no later than September after spawning. 2) On the other hand, another half of males of age group II⁺ continued to grow in summer and became matured at III⁺ year old in the following summer. These II⁺ males were termed “non-mature” males against the above mentioned mature males. These males showed no secondary sexual characteristics and having only thin thread-like testis through out the spawning season. 3) The morphological change of anal fin was observed also in mature females, but to a lesser extent as compared with mature males. Mature females began to spawn at II⁺ years and died out after the second spawning at III+ years. 4) It is evident that Zacco platypus more than 80 mm in total length can be sexed during spawning season and the degree of the sexual maturation, particularly in the males, may be quantitatively measured by the length of anal fin. 5) The cause of the condition that males of age group II+ are mature or “non-mature” in spawning season was suggested through reading the history on the scales examined. The appearance of “non-mature” males in age group II⁺ was discussed in relation to the population density.

収録刊行物

• 魚類学雑誌

  魚類学雑誌 16 (1), 17-23, 1969

  The Ichthyological Society of Japan

詳細情報

• CRID: 1390001204768185856
• NII論文ID: 130003825865
• DOI: 10.11369/jji1950.16.17
• ISSN: 18847374
• ISSN: 00215090
• データソース種別:
  • JaLC
  • CiNii Articles
• 抄録ライセンスフラグ: 使用不可