Oogenesis and Changes in the Levels of Reproductive Hormones in Triploid Female Rainbow Trout

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  • Kobayashi Toru
    Shiga Prefectural Samegai Trout Farm Department of Fisheries, Faculty of Agriculture, Kinki University
  • Fushiki Shozo
    Shiga Prefectural Samegai Trout Farm Fisheries Laboratory of Kinki University
  • Sakai Noriyoshi
    Shiga Prefectural Samegai Trout Farm Department of Marine Bioscience, Fukui Prefectural University
  • Hara Akihiko
    Nanae Fish Culture Experimental Station, Faculty of Fisheries, Hokkaido University
  • Amano Masafumi
    Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo School of Fisheries Sciences, Kitasato University
  • Aida Katsumi
    Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo
  • Nakamura Masaru
    Faculty of Medicine, Teikyo University
  • Nagahama Yoshitaka
    National Institute ofr Basic Biology

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  • Oogenesis and Changes in the Levels of

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Abstract

The reproduction of artificially induced triploid rainbow trout was histologically and endocrinologically examined during three consecutive seasons. The gonadosomatic indices of triploid females were much lower (0.02-0.06) than the indices of diploid females. The concentrations of sex steroid hormones, including testosterone, estradiol-17β, and 17α, 20β-dihydroxy-4-pregnen-3-one, were much lower than those of diploid females but had small changes, and changes of gonadotropin (GtH) levels in the serum of triploid females differed from those of diploid females. Oogenesis in the triploid ovary was substantially delayed, and most germ cells ceased to develop at the synaptic stage of the first meiotic division. At three years old, various developmental stages of oocytes were detected in the ovary, such as peri-nucleolus, yolk vesicle, and early yolk globule stage. It seemed that these rare developments of triploid oocytes were related to the small increases of steroid hormone concentrations and rise of GtH level that appeared when fish were two years old and three years old. Nevertheless, even in triploid ovarian oocytes grown to secondary yolk globule stage, the germinal vesicles did not migrate and there was no ovulation. It was confirmed that triploid liver cells possessed the potential to produce vitellogenin. These results suggest that the genital gland of triploid females is undeveloped because the odd number of chromosome sets causes the first maturation division to fail, and the endocrinological abnormality.

Journal

  • Fisheries science

    Fisheries science 64 (2), 206-215, 1998

    The Japanese Society of Fisheries Science

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