キンギョとメダカにおけるX線被照射量と生存期間との関係

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In order to obtain some information about the causation of radiation death in teleosts, the relationship between the period of survival following exposure to X-rays and dose of the irradiation was examined with the goldfish, Carassius auratus and the medaka, Oryzias latipes. Common goldfishes and red variety of medaka were irradiated with 1/4, 1/2, 1, 2, 4, 8, 16, 32, 64 or 128kr of X-rays (200kvp, 20ma, with 0.5mmAl and 0.5mmCu filters, 400r/min. in air). During irradiation, each group of fishes composed of unanesthetized 5-8 goldfishes or 20-25 medaka, was kept in a small cylindrical lucite vessel containing water. Immediately after the irradiation, each group of fishes was transferred into larger tank and kept at 22-23℃. Besides, non-irradiated fishes served as controls. In total, 13 series of experiments were carried out with 868 goldfishes, and 27 series with 2, 114 medaka. The number of dead fishes was recorded every day after irradiation. Mean survival time after irradiation in each dose lot was calculated (Tables 1, 2 and 3), and the sose-survival time relationship curves were constructed (Fig. 2). The results are summarized as follows: (1) A single irradiation of fishes of both species with 1kr or less produces no marked change in the mortality at least within 30 post-irradiation days. (2) In 2kr-irradiated lot, about 80 per cent (in goldfish) or 50 per cent (in medaka) of fishes die by the 30th day, the mortality being significantly higher than in the lower dose lots. From the sistribution of the survival times of fishes, it is found that majority of medaka irradiated with 2kr die during two different limited periods, varying from 9-15 and 60-100 days. (3) In most fishes irradiated with 4-32kr, the length of survival time varies within a limited range, varying from 7 to 13 days (mean survival time: 9 days in goldfish, 10 days in medaka), regardless of the irradiated dose ("dose-independent range"). (4) Following 64kr irradiation, some goldfishes die instantaneously, but the rest survive until 3-13 post irradiation days. However, no sudden death takes place in medaka following exposure to 64kr of X-rays. (5) The largest dose, 128kr, kills all fishes of both species instantaneously. It is concluded that there are several distinct ranges of X-ray doses over which causes leading to death are different. At least three different kinds of radiation death are distinguishable in the fishes. Furthermore, the dose-survival time relationships found in the fishes were compared with those in mammals, and the reason for the difference found between these two classes of vertebrates were disscussed.
社団法人日本動物学会の論文
1962-10-15

キンギョとメダカにおけるX線被照射量と生存期間との関係

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