The reproductive status of Steller sea lions in the Nemuro Strait, Hokkaido, Japan

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  • Ishinazaka Tsuyoshi
    Laboratory of Veterinary Physiology, College of Bioresource Sciences, Nihon University Present address: Laboratory of Wildlife Biology, Graduate School of Veterinary Medicine, Hokkaido University
  • Endo Tsuyoshi
    Laboratory of Veterinary Physiology, College of Bioresource Sciences, Nihon University

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Description

The reproductive tracts of 29 female Steller sea lions Eumetopias jubatus collected in the Nemuro Strait, Hokkaido, Japan, during the winters of 1995 and 1996, were examined to estimate their reproductive histories and status. After sectioning ovaries at intervale of 250μm thickness, a light microscope was used to examine 23 of the 57 ovaries for small retrograde corpora lutea (RCLs). None of the RCLs that were more than three years old were found. The regression process of an RCL is presumed to occur rapidly because of the pressure exerted by a large corpus luteum of pregnancy (PCL) formed during the subsequent pregnancy. No more than three placental scars were found in any one female, probably because the scars disappeared during placentation during subsequent pregnancies. Thus, estimations of the reproductive histories of Steller sea lions were not possible beyond three years. Females became sexually mature from four to seven years of age, which was one year later than in previous studies (Perlov 1971). Among those sampled during January and February, the pregnancy rate for females that had ovulated was 88.5% (23/26).

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Details 詳細情報について

  • CRID
    1390282681070678528
  • NII Article ID
    110001817306
  • NII Book ID
    AA11499342
  • DOI
    10.20798/biospherecons.2.1_11
  • ISSN
    24331260
    13446797
  • Text Lang
    en
  • Data Source
    • JaLC
    • CiNii Articles
  • Abstract License Flag
    Disallowed

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