Data from: Mechanisms and fitness effects of antibacterial defenses in a carrion beetle

Parents of many species care for their offspring by protecting them from a wide range of environmental hazards, including desiccation, food shortages, predators, competitors, and parasites and pathogens. Currently, little is known about the mechanisms and fitness consequences of parental defenses against bacterial pathogens and competitors. Here we combine approaches from microbiology and behavioural ecology to investigate the role and mechanistic basis of antibacterial secretions applied to carcasses by parents of the burying beetle Nicrophorus vespilloides. This species rears its larvae on vertebrate carcasses, where larvae suffer significant fitness costs due to competition with bacterial decomposers. We first confirm that anal secretions produced by parents are potently bactericidal, and that their effects are specific to gram-positive bacteria. Next, we identify the source of bacterial killing as a secreted lysozyme, and show that its concentration changes throughout the breeding cycle. Finally, we show that secreted lysozyme is crucial for larval development, increasing survival by nearly two-fold compared to offspring reared in its absence. These results demonstrate for the first time that anal secretions applied to carrion is a form of parental care, and expand the mechanistic repertoire of defenses used by parent insects to protect dependent offspring from microbial threats.诸多物种的亲代都会通过保护子代免受多种环境危害来抚育后代，这些危害包括干燥脱水、食物短缺、捕食者、竞争者以及寄生虫与病原体。目前学界对亲代抵御细菌病原体与竞争者的防御机制及其适合度影响仍知之甚少。本研究结合微生物学与行为生态学的研究方法，对埋葬甲（Nicrophorus vespilloides）亲代涂抹于尸体上的抗菌分泌物的作用及其机制基础展开探究。该物种将幼虫培育于脊椎动物尸体之上，幼虫会因与细菌分解者竞争而承受显著的适合度损失。首先，我们证实亲代产生的肛门分泌物具有强效杀菌活性，且其作用仅针对革兰氏阳性细菌。其次，我们明确了杀菌活性的来源为分泌型溶菌酶，并证实其浓度在整个繁殖周期中会发生动态变化。最后，我们证实分泌型溶菌酶对幼虫发育至关重要，与缺乏该酶的抚育组相比，其可使幼虫存活率提升近一倍。本研究首次证实，涂抹于腐肉上的肛门分泌物属于亲代抚育行为的一种，并拓展了昆虫亲代用于保护依赖型子代免受微生物威胁的防御机制库。