Seasonal Changes in Ovarian Response to Photoperiods in Orange-Red Type Medaka : Reproductive Biology

概要

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Three groups of orange-red type medaka. Oryzias latipes, were reared from October under different temperature-photoperiod regimes: natural condition, 18℃ natural daylength and natural temperature 15L (15hr of light/day). Pairs from these groups were periodically transferred to 18℃ 15L or to 18℃C 10L and kept separately. In natural condition group, ovaries of the fish transferred in mid- or late October kept immature even after one month under both regimes. In the fish transferred in late November or late December, ovarian growth and spawning were observed in about one month only under 18℃ 15L. The fish transferred in early February matured in three weeks and spawned irrespective of photoperiod. Thus, ovarian refractoriness in autumn changed into long-daylength dependent maturation in winter, which was followed by photoperiod independent maturation in spring. In the fish transferred from 18℃ natural daylength and natural temperature 15L in late December and early February, rapid ovarian growth occurred under 18℃ 15L, but not under 18℃ 10L. These results demonstrate that ovarian response to temperature-photoperiod conditions can be markedly influenced by environmental careers in medaka.
社団法人日本動物学会の論文
1989-10-15