Changes in haemolymph parameters and insect ability to respond to immune challenge during overwintering (Ecology and Evolution)

Overwintering is a challenging period in the life of temperate insects. A limited energy budget characteristic of this period can result in reduced investment in immune system. Here, we investigated selected physiological and immunological parameters in laboratory-reared and field-collected harlequin ladybirds (Harmonia axyridis). For laboratory-reared beetles, we focused on the effects of winter temperature regime (cold, average or warm winter) on total haemocyte concentration aiming to investigate potential effects of ongoing climate change on immune system in overwintering insects. We recorded strong reduction in haemocyte concentration during winter, however, there were only limited effects of winter temperature regime on changes in haemocyte concentration in the course of overwintering. For field-collected beetles, we measured additional parameters, specifically: total protein concentration, antimicrobial activity against Escherichia coli and haemocyte concentration before and after overwintering. The field experiment did not investigated effects of winter temperature, but focused on changes in inducibility of insect immune system during overwintering, i.e., measured parameters were compared between naïve beetles and those challenged by E. coli. Haemocyte concentration decreased during overwintering, but only in individuals challenged by E. coli. Prior to overwintering, the challenged beetles had a significantly higher haemocyte concentration compared to naïve beetles, whereas no difference was observed after overwintering. A similar pattern was observed also for antimicrobial activity against E. coli as challenged beetles outperformed naïve beetles before overwintering, but not after winter. In both sexes, total protein concentration increased in the course of overwintering, but females had a significantly higher total protein concentration in their haemolymph compared to males. In general, our results revealed that insect’s ability to respond to an immune challenge is significantly reduced in the course of overwintering. All raw data collected during this study are stored here.越冬是温带昆虫生活史中极具挑战性的阶段。该阶段普遍存在的能量预算受限问题，会导致昆虫对免疫系统的资源投入减少。本研究以实验室饲养和野外采集的异色瓢虫（Harmonia axyridis）为研究对象，对其部分生理与免疫相关参数展开了探究。针对实验室饲养的瓢虫，我们重点探究了越冬温度条件（低温、常温或暖冬）对血细胞（haemocyte）总浓度的影响，以期揭示当前气候变化对越冬昆虫免疫系统的潜在效应。我们观测到，越冬期间血细胞浓度显著降低，但越冬温度条件对越冬过程中血细胞浓度的变化仅存在微弱影响。对于野外采集的瓢虫，我们额外测定了多项参数，具体包括：越冬前后的总蛋白浓度、抗大肠埃希氏菌（Escherichia coli）抗菌活性以及血细胞总浓度。野外实验未探究越冬温度的影响，而是聚焦于越冬过程中昆虫免疫系统诱导性的变化，即对未受免疫刺激的瓢虫与经大肠埃希氏菌免疫刺激的瓢虫的测定参数进行了对比。仅在经大肠埃希氏菌免疫刺激的个体中，越冬期间的血细胞浓度出现了下降。越冬前，经免疫刺激的瓢虫血细胞浓度显著高于未受刺激个体，但越冬后二者无明显差异。抗大肠埃希氏菌的抗菌活性也呈现出相似的模式：越冬前经免疫刺激的瓢虫抗菌活性优于未受刺激个体，但越冬后则无此差异。无论雌雄，越冬过程中血淋巴（haemolymph）总蛋白浓度均有所上升，但雌性个体的血淋巴总蛋白浓度显著高于雄性。总体而言，本研究结果表明，昆虫应对免疫刺激的能力在越冬过程中显著下降。本研究采集的所有原始数据均存储于此。