Sexual maturity of the Isaza, Chaenogobius isaza IV. Vitellogenesis and the Subjective Diel Thermoperiod Caused by Verical Migration

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The relationship between vitellogenesis in Isaza and the diel thermoperiod, which is experienced by the Isaza as a result of their diel vertical migration, were studied. The oocytes of fish exposed to temperatures higher than 14-15℃ did not start vitellogenesis. Even though the average temperature was below the threshold (14-15℃), a diel thermoperiod between 10-20℃ inhibited the onset of vitellogenesis. When the temperature of the high-temperature phase was lowered to below 16-18℃, vitellogenesis began. It appears necessary to experience a high temperature of around 20℃ before the onset of vitellogenesis, however, for the normal development of oocytes. The onset of vitellogenesis in Isaza in nature is triggered synchronously in late-October, when the water temperature of the upper stratum where the Isaza swim up every night drops to around 16℃. This is in good agreement with the experimental results. To migrate between the lake bottom and the upper layer every day is thus necessary for the Isaza to start normal vitellogenesis synchronously at the appropriate season.
社団法人日本動物学会の論文
1982-03-25