<研究論文>ルリカケスの繁殖に伴う性ホルモン分泌の季節変動

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The purple jay is an endemic species to Japan. The species was hunted down in the ealy part of 1900's to be classified "Vulnerable" in the Red Database. The reports on the ecology of purple jays have been known, but none reported the physiological research. The present authors therefore examined a pair of adult purple jays kept in a zoo to know the changes in their sex hormones and reproductive behaviors for 19 months which included two breeding seasons. Sex hormones were examined by means of measuring fecal hormone amounts. The pair showed their breeding activities between January and May each time. Egg-laying preiods followed nesting, but when incubation was experimentally interrupted, they began all over again by reverting to nest-making and egg-laying. It was then established that estradiol (E_2) showed high only during the breeding period. The high values coincided with egg-laying, and the interrupted incubation lowered the amount. Testosterone (T) also was observed to rise not only during the breeding period but also in autumn. Progesterone (P) was high during the breeding season but showed high during the molting period, which makes this hormone differ from the other two hormones. These results clearly suggest that the change in the amount of E_2 and T secreted are deeply connected with the breeding mechanism. The shift of P during the breeding period was considered connected to the nesting and egg-laying.
2001-12-25