プラナリアには季節変化に応じて, 無性生殖と有性生殖を転換する個体が存在する。本課題では生殖様式転換を誘起する環境因子を解明するために, 沖縄で1年を通して定期的に採集し, 実験室内の一定環境下で飼育したのちも生殖様式の転換が観察される系統(転換系統)を確立した。転換系統に対して, 夏期の無性生殖状態の転換系統個体に対して明期10時間, 暗期14時間, 15℃(低温)の冬条件で飼育したところ, 有性生殖に転換した。しかし, 転換系の性質は実験室環境下では3年以上は維持することができないことがわかった。本実験の継続させるためには, 恒常的に新たな転換系統を確立することが必要である。
There are races in planarian with switching of reproduction modes of between asexual and sexual, depending on the change of season. To identify the environmental parameter to induce the switching of reproduction modes, we collected Dugeisa ryukyuensis regularly in Okinawa through one year and established some strains, which switch between sexual mode and asexual mode under the constant environment in the laboratory (called as switching mode). The worms of the switching mode were asexual mode in summer. When their living condition had been changed from summer condition to winter condition (15 C in temperature and 10L14D in photoperiod), their reproduction modes were switched from asexual to sexual. Unfortunately, worms of switching modes could not maintained their characters during three years or more. Therefore, it is necessary to constantly established some new strains, which switch between sexual mode and asexual mode under the constant environment for this experiment.
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