Imroze K, Prasad N G
Indian Institute of Science Education and Research, BCVK Campus, Mohanpur 741 252, India.
J Genet. 2011 Dec;90(3):427-34. doi: 10.1007/s12041-011-0105-7.
Mating has been widely reported to be a costly event for females. Studies indicate that female cost of mating in terms of fecundity and survivorship can be affected by their mates, leading to antagonistic coevolution between the sexes. However, as of now, there is no evidence that the female cost of mating in terms of immune defence is affected by their mates. We assess the effect of different sized males on antibacterial immune defence and reproductive fitness of their mates. We used a large outbred population of Drososphila melanogaster as the host and Serratia marcescens as the pathogen. We generated three different male phenotypes: small, medium and large, by manipulating larval densities. Compared to females mating with small males, those mating with large males had higher bacterial loads and lower fecundity. There was no significant effect of male phenotype on the fraction of females mated or copulation duration (an indicator of ejaculate investment). Thus, our study is the first clear demonstration that male phenotype can affect the cost of mating to females in terms of their antibacterial immune defence. Mating with large males imposes an additional cost of mating to females in terms of reduced immune defence. The observed results are very likely due to qualitative/quantitative differences in the ejaculates of the three different types of males. If the phenotypic variation that we observed in males in our study is mirrored by genetic variation, then, it can potentially lead to antagonistic coevolution of the sexes over immune defence.
交配对于雌性来说是一项代价高昂的活动，这一点已被广泛报道。研究表明，雌性在繁殖力和存活率方面的交配成本可能会受到配偶的影响，从而导致两性之间的对抗性协同进化。然而，截至目前，尚无证据表明雌性在免疫防御方面的交配成本会受到配偶的影响。我们评估了不同体型雄性对其配偶的抗菌免疫防御和生殖适应性的影响。我们以大量远交的黑腹果蝇群体作为宿主，以粘质沙雷氏菌作为病原体。通过控制幼虫密度，我们产生了三种不同的雄性表型：小、中、大。与与小体型雄性交配的雌性相比，与大体型雄性交配的雌性细菌载量更高，繁殖力更低。雄性表型对交配雌性的比例或交配持续时间（射精投入的一个指标）没有显著影响。因此，我们的研究首次明确证明，雄性表型会在抗菌免疫防御方面影响雌性的交配成本。与大体型雄性交配会使雌性在免疫防御降低方面承担额外的交配成本。观察到的结果很可能是由于三种不同类型雄性射精的质量/数量差异所致。如果我们在研究中观察到的雄性表型变异反映了基因变异，那么，这可能会导致两性在免疫防御方面的对抗性协同进化。
