- 學位論文
多次交尾對四紋豆象雌蟲繁殖力之作用
The Effect of Multiple-Mating on the Reproduction of Female Seed Beetle (Callosobruchus maculatus (F.))
摘要
由於有性生殖生物在配子上的分化，理論上，藉由增加交尾次數來提升生殖成功 (reproductive success) 對雄性而言較為顯著，然而我們仍可觀察到許多種雌性昆蟲表現多次交尾的行為。本實驗觀察一次和兩次交尾的四紋豆象雌成蟲之生活史特質表現，來探討多次交尾對雌蟲造成的影響。結果發現兩次交尾的雌蟲之壽命、總產卵量和體重損失皆較一次交尾的雌蟲高，表示多次交尾可以延長雌蟲的壽命，且刺激雌蟲花費更多的能量來產下更多的後代。而觀察雌蟲的每日產卵數發現兩次交尾的雌蟲在第二次交尾當天，其日產卵數顯著增加，表示再次交尾可以立即增加產卵的速率；然而，若只進行機械式交尾來阻止雄性物質之傳送，則產卵速率並不會增加，顯示可能有某種刺激產卵的物質存在於雄蟲的精液內。另檢驗雌蟲本身體重的損失或雄蟲的精胞大小與總產卵量的關係時，發現一次及兩次交尾的雌蟲體重損失與總產卵量皆有顯著的正相關；然而，雄蟲的精胞大小與雌蟲的總產卵量只在兩次交尾時有正相關，推測雄蟲只有在雌蟲進行多次交尾時，才能對雌蟲之產卵能力造成影響。此外，在解剖實驗中，發現再次交尾並無法立即增加雌蟲卵成熟的速率(egg maturation rate)，然而在往後幾天卻有卵成熟速率較快的現象。據此，本論文提出間接驅動卵成熟假說(indirect driven hypothesis)，並證明雌蟲於再次交尾當天產卵速率的加快造成側輸卵管的載卵壓力降低，可以引發後來排卵速率的增加。因此，多次交尾可以藉由額外的雄性交尾傳遞物質來刺激雌蟲產卵，並間接加速卵的成熟，藉此提高雌蟲的生殖成功。
並列摘要
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.
參考文獻
延伸閱讀
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