Delayed sperm injection and fertilization in parthenogenetically activated insect egg (Athalia rosae, Hymenoptera).

Mature eggs dissected from the ovary of unmated females of Athalia rosae ruficornis Jakovlev (Hymenoptera, Tenthredinidae) can be activated to develop (into haploid parthenogenetic males) simply by exposing them to distilled water. These eggs, which are primary oocytes arrested at the first meiotic metaphase, resume meiosis upon activation and reach the first meiotic telophase in 20 min. Mature eggs immediately upon dissection have previously been shown to complete karyogamy and develop as fertilized diploid females if injected with sperm. We show here that the eggs activated in water for 20 min have a much higher rate of successful fertilization if injected with sperm, and that the eggs activated for 40 min, upon sperm injection, though at a reduced frequency still develop as diploid fertilized females. Eggs left in water for 60 min, however, are no longer fertilized upon sperm injection and develop as haploid males.