アユの内分泌腺に関する研究-8-光週期を統御したコアユの胸腺にみられた退行変化〔英文〕

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The annual salmonoid fish, Koayu was reared in outdoor hatchery ponds exposed to short (8 hours), long (16 hours), and natural photoperiods (control). These, as well as Otunen-Ayu that survived spawning and was collected in the streams of the suburbs of Niigata City, were examined histologically to elucidate the involution and regression of the thymus. Age involution of this organ commences with gonad maturation. A remarkable decrease in the number of lymphocytes and their mitotic divisions occurs, and at the same time an increase in the amount of reticular and collagenous fibers around the vessels and development of cystic spaces take place. The connective tissues and spaces disappear toward the end of involution. These regressive changes, including the disappearance of the thymus, occurred one month earlier in the short-photoperiod group than in the control group, but under the long photoperiod one to two months later than in the controls. The thymus was absent in all the Otunen-Ayu examined.
日本水産學會の論文