| Summary: | 碩士 === 國立臺灣大學 === 昆蟲學研究所 === 92 === In general, females do not increase their reproductive success linearly by mating multiply as males do. However, an evolutionary inclination to mate multiply in females has been observed in a variety of insect species. In this study, I tried to determine the potential function of additional matings for female Callosobruchus maculatus by permitting them to mate either singly or doubly at a 48 hours interval. The longevity, lifetime fecundity, and total weight loss were higher in the doubly mated females, suggesting that females could prolong their longevity, and invest more weight for laying more eggs through an additional mating. Of daily egg production, there was an immediate increase of egg production on the remating day in the doubly mated females, thus remating could promote females to increase daily egg production immediately. However, this increase of egg production disappeared when females were mated only through a mechanical copulation, which transferred no ejaculate to females. Moreover, there was positive correlation between male ejaculate size and female lifetime fecundity when females were mated doubly. It is suggested that there should be certain material(s) stimulating females to increase egg production in male ejaculate and transferred to females during copulation, but these materials obviously functioned as egg production stimulus only after second mating. To understand the mechanism of egg production increased by multiple mating, the dissection of female ovaries was carried out 24 hours after remating. It showed that the number of eggs unlaid was lower in doubly mated female, while the eggs laid was considerably high, suggesting that the second mating increased only oviposition rate, but did not drive egg maturation rate directly in female C. maculatus. Indirect driven hypothesis that states the increased egg maturation rate on the following day after remating was driven under the decrease of egg-load pressure was proposed. By depriving of their hosts for 3 days after remating to inhibit oviposition, I was able to support this hypothesis because the increase of egg production disappeared in the doubly mated females that were deprived of hosts. This is due to that the number of eggs unlaid remained high. Therefore, in C. maculatus, multiple mating for females could contribute to reproduction success through direct effect of increasing oviposition and indirect effect of increasing egg maturation.
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