Cytoplasmic Incompatibility in a Natural Population of Culex pipiens Complex in Nagasaki, Japan

1981年5月から10月まで長崎市内の屋外に容量18リットルの水がめを設置し,実験マウス用固型配合飼料を溶かした水を入れ,毎日観察して水面に産み落されたアカイエカ群の卵魂を採集し,25℃の飼育室内で孵化状況を調べると共に,一部の卵塊から孵化したものを卵塊別に飼育して交雑実験に供した.また,一部の卵塊から飼育,羽化させた雌成虫については羽化直後に卵巣を取り出してストライドグラス上に塗沫し,ギムザ染色してwolbachiae の有無を調べた.全期間を通じて採集された481卵塊の中, 474塊は高率に孵化したが,7～8月に採れた7卵塊ほ何れも幾つかの卵がかなり発育していながら全く孵化せず,不和合交雑の結果産まれた可能性を示唆した.交雑実験の結果,チカイエカの1型とアカイエカの2型の3つの異なる交雑型が同じ発生水域から出現したことがわかった.また,沖縄原産のネッタイイエカは更に異なる交雑型であることが確かめられた.交雑実験に使われたすべての系統は何れも卵巣肺胞内に多数のリケッチア様微生物wolbachiaeを保有していた.An earthen jar containing mouse food solution was set up as an ovi-trap for house mosquitoes outside a building in Nagasaki during May through October, 1980. While 474 or 98.5% out of 481 egg rafts collected have hatched well, 7 or 1.5% did not hatch, although each of them have contained some developed eggs respectively. Thirteen or 7.6% out of 172 egg rafts examined were Culex pipiens molestus and the others were Cx. pipiens pallens. The results of the crossing experiments with 32 strains collected by the ovi-trap in Nagasaki showed the presence of 3 crossing types, that is one type of Cx. pipiens molestus (A) and 2 types (B and C) of Cx. pipiens pallens. One strain of Cx. pipiens quinquefasciatus from Okinawa showed the different crossing type (D). The appearance of unhatched egg rafts containing some developed eggs suggested that the egg rafts had been laid by the females which mated with incompatible males in the field. All of 33 strains used for the crossing experiments have been heavily infected with Wolbachia pipientis respectively