Chechi Tejinder Singh, Ali Syed Zeeshan, Prasad Nagaraj Guru
Indian Institute of Science Education and Research, Mohali, Knowledge City, Sector 81, SAS Nagar, Mohali, Punjab 140306, India.
Indian Institute of Science Education and Research, Mohali, Knowledge City, Sector 81, SAS Nagar, Mohali, Punjab 140306, India.
J Insect Physiol. 2017 Apr;98:67-73. doi: 10.1016/j.jinsphys.2016.11.012. Epub 2016 Nov 29.
Sperm competition theory predicts that with increase in sperm competition, males either invest more in reproductive organ(s) and/or improve ejaculate investment. We test this idea using experimental evolution in Drosophila melanogaster. We maintained replicate populations of Drosophila melanogaster under male (M) and female (F) biased sex ratio regimes for more than a hundred generations with the result that males from the M regime evolved higher sperm competitive abilities relative to males from the F regime. In the present study, we measured the testes and the accessory gland size of virgin and singly mated males from the M and F regimes. The M and F males do not differ in either testis or accessory gland size. Additionally, ejaculate investment is not different in the M and F males, as measured by reduction in testis and accessory gland sizes. Thus, contrary to theoretical prediction and evidence from other species, we found that evolved differences in sperm competitive ability are not necessarily due to evolution of testis/accessory gland size or strategic ejaculate investment in these populations.
精子竞争理论预测，随着精子竞争的增加，雄性要么在生殖器官上投入更多，和/或增加射精投入。我们利用黑腹果蝇的实验进化来验证这一观点。我们在雄性（M）和雌性（F）偏态性别比例条件下维持黑腹果蝇的重复种群超过一百代，结果是，相对于来自F条件的雄性，来自M条件的雄性进化出了更高的精子竞争能力。在本研究中，我们测量了来自M和F条件的未交配和单配雄性的睾丸和附腺大小。M和F雄性在睾丸或附腺大小上没有差异。此外，通过睾丸和附腺大小的减少来衡量，M和F雄性的射精投入也没有差异。因此，与理论预测和其他物种的证据相反，我们发现精子竞争能力的进化差异不一定是由于这些种群中睾丸/附腺大小的进化或策略性射精投入。
