Data from: Seminal fluid of honeybees contains multiple mechanisms to combat infections of the sexually transmitted pathogen Nosema apis

The societies of ants, bees and wasps are genetically closed systems where queens only mate during a brief mating episode prior to their eusocial life and males therefore provide queens with a lifetime supply of high-quality sperm. These ejaculates also contain a number of defence proteins that have been detected in the seminal fluid but their function and efficiency have never been investigated in great detail. Here, we used the honeybee Apis mellifera and quantified whether seminal fluid is able to combat infections of the fungal pathogen Nosema apis, a widespread honeybee parasite that is also sexually transmitted. We provide the first empirical evidence that seminal fluid has a remarkable antimicrobial activity against N. apis spores and that antimicrobial seminal fluid components kill spores in multiple ways. The protein fraction of seminal fluid induces extracellular spore germination, which disrupts the life cycle of N. apis, whereas the non-protein fraction of seminal fluid induces a direct viability loss of intact spores. We conclude that males provide their ejaculates with efficient antimicrobial molecules that are able to kill N. apis spores and thereby reduce the risk of disease transmission during mating. Our findings could be of broader significance to master honeybee diseases in managed honeybee stock in the future.

蚂蚁、蜜蜂与胡蜂的社会体系属于遗传封闭系统：蚁后、蜂后仅会在进入真社会性（eusocial）生活前的短暂交配期内完成交配，因此雄性可为蜂后、蚁后提供终生可用的高质量精子。这些射精产物中含有多种已在精浆（seminal fluid）中被检出的防御蛋白，但其功能与效能尚未得到深入研究。本研究以西方蜜蜂（Apis mellifera）为实验对象，定量分析了精浆是否能够抵御真菌病原体蜂微孢子虫（Nosema apis）的感染——该寄生虫广泛分布于蜂群中，同时可通过性接触传播。本研究首次提供实验证据表明，精浆对蜂微孢子虫孢子具有显著的抗菌活性，且精浆中的抗菌成分可通过多种途径杀灭孢子：精浆的蛋白组分可诱导孢子胞外萌发，从而扰乱蜂微孢子虫的生活史；而精浆的非蛋白组分则可直接导致完整孢子丧失活力。综上，雄性射精产物中含有高效抗菌分子，可杀灭蜂微孢子虫孢子，进而降低交配过程中的疾病传播风险。本研究结果未来或可为人工饲养蜂群的蜜蜂病害防控提供更广泛的应用价值。