Pusceddu Michelina, Tragust Simon, Theodorou Panagiotis, Ciabattini Bolla Irene, Sánchez Navarro Jorge, Corrias Francesco, Atzei Alessandro, Angioni Alberto, Floris Ignazio, Satta Alberto
Department of Agricultural Sciences, Section of Plant Pathology and Entomology, University of Sassari, Sassari, Italy.
National Biodiversity Future Center (NBFC), Palermo, Italy.
Sci Rep. 2025 Aug 20;15(1):30623. doi: 10.1038/s41598-025-13440-2.
Social insects employ venom as an external immune defence against pathogens and parasites. Like other Hymenopterans, the venom gland of honey bee (Apis mellifera) serves as a reservoir of antimicrobial substances, primarily melittin. This study investigated the presence and origin of venom on honey bee body that could act as an external immune defence in honey bee workers infested by the ectoparasite mite, Varroa destructor. Using a multi-step approach, we first confirmed the presence of venom on bees' bodies using melittin as a marker. We then examined how grooming could facilitate the distribution of venom on the bee's body through behavioural observations. Further assays were used to compare melittin levels on the bodies of Varroa-free and Varroa-infested workers and assess the effects of bee-venom on mite activity. Our findings confirmed the occurrence of "venom bathing" in A. mellifera, excluding social components or environmental contamination, with bees likely coating their bodies with antimicrobial substances through self-grooming. Our results further suggest that infested bees spread higher amount of venom on their bodies compared to uninfested bees, and bee-venom significantly reduced mite activity, suggesting that the venom functions as an external defence. However, Varroa negatively impacted melittin production. Our study reveals a previously unknown negative effect of V. destructor: impairment of honey bees' external immune defence through reduced melittin production.
群居昆虫将毒液作为抵御病原体和寄生虫的外部免疫防御手段。与其他膜翅目昆虫一样，蜜蜂（西方蜜蜂）的毒腺是抗菌物质的储存库，主要是蜂毒肽。本研究调查了蜜蜂身体上毒液的存在情况及其来源，这些毒液可能在受到体外寄生虫瓦螨侵害的工蜂中起到外部免疫防御作用。我们采用多步骤方法，首先以蜂毒肽为标志物确认了蜜蜂身体上存在毒液。然后通过行为观察研究梳理行为如何促进毒液在蜜蜂身体上的分布。进一步的实验用于比较无瓦螨和感染瓦螨的工蜂身体上的蜂毒肽水平，并评估蜂毒对螨虫活动的影响。我们的研究结果证实了西方蜜蜂中存在“毒液沐浴”现象，排除了社会因素或环境污染，蜜蜂可能通过自我梳理用抗菌物质覆盖身体。我们的结果还表明，与未感染的蜜蜂相比，感染的蜜蜂在身体上散布的毒液量更高，且蜂毒显著降低了螨虫活动，这表明毒液起到了外部防御作用。然而，瓦螨对蜂毒肽的产生有负面影响。我们的研究揭示了瓦螨一种此前未知的负面影响：通过减少蜂毒肽的产生损害蜜蜂的外部免疫防御。
