Animal Population Ecology, Animal Ecology I, University of Bayreuth, Universitätsstraße 30, 95440 Bayreuth, Germany.
Animal Population Ecology, Animal Ecology I, University of Bayreuth, Universitätsstraße 30, 95440 Bayreuth, Germany.
J Insect Physiol. 2020 May-Jun;123:104048. doi: 10.1016/j.jinsphys.2020.104048. Epub 2020 Mar 13.
Besides typical sexually transmitted microbes, even environmental, opportunistic microbes have been found in copulatory organs of insects and even humans. To date, only one study has experimentally investigated the sexual transmission of opportunistic microbes from male to female insects, whereas nothing is known about the transmission from females to males. Even if opportunistic microbes do not cause infection upon transmission, they might eventually become harmful if they multiply inside the female. While the immune system of females is often assumed to target sexually transmitted microbes, most studies ignore the role of mating-associated opportunistic microbes. Variation in immunity between populations has been linked to parasite or bacteria prevalence but no study has ever addressed between-population differences in immune responses to sexually transmitted opportunistic microbes. We here show that bacteria applied to the copulatory organs of common bedbugs, Cimex lectularius, are sexually transmitted to the opposite sex at a high rate, including the transmission from female to male. Bacterial growth in the female sperm-receiving organ was inhibited over the first hours after introduction, but after this initial inhibition bacterial numbers increased, suggesting a shift of investment from immune defence towards reproduction. However, 24 h after the injection of bacteria, male components, or saline as a control, the sperm-receiving organ showed lysozyme-like activity and inhibited the growth of Gram-negative and Gram-positive bacteria in vitro, potentially to mop up the remaining bacteria. Contrasting our prediction, neither bacterial growth nor immune responses differed between populations. Future studies should link transmission dynamics, immune responses and fitness effects in both sexes. Experimental manipulation of environmental bacteria could be used to investigate how transmission frequency and toxicity of sexually transmitted opportunistic microbes shapes bacteria clearance and immune responses across populations.
除了典型的性传播微生物外，甚至在昆虫的交配器官中，甚至在人类的交配器官中，也发现了环境性机会微生物。迄今为止，只有一项研究从雄性到雌性昆虫实验性地研究了机会性微生物的性传播，而对于从雌性到雄性的传播则一无所知。即使机会性微生物在传播时不会引起感染，如果它们在雌性体内繁殖，它们最终可能会变得有害。虽然女性的免疫系统通常被认为针对性传播微生物，但大多数研究忽略了与交配相关的机会性微生物的作用。种群之间的免疫变异与寄生虫或细菌的流行有关，但没有研究探讨过对性传播机会性微生物的免疫反应的种群间差异。我们在这里表明，将细菌应用于常见的臭虫（Cimex lectularius）的交配器官中，可以以很高的比率将其性传播给异性，包括从雌性传播到雄性。细菌在雌性接受精子的器官中生长在引入后的前几个小时受到抑制，但在此初始抑制之后，细菌数量增加，表明投资从免疫防御转向繁殖。然而，在注射细菌、雄性成分或盐水作为对照 24 小时后，接受精子的器官显示出溶菌酶样活性，并抑制了革兰氏阴性和革兰氏阳性细菌的体外生长，可能是为了清除剩余的细菌。与我们的预测相反，细菌生长和免疫反应在种群之间没有差异。未来的研究应该将两性的传播动态、免疫反应和适合度效应联系起来。对环境细菌的实验性操纵可以用来研究性传播机会性微生物的传播频率和毒性如何影响细菌清除和免疫反应在不同种群之间的变化。
