Non-Consumptive Effects of Harmonia axyridis on the Reproduction and Metabolism of Spodoptera frugiperda.

Simple Summary: This study investigated the non-consumptive effects of Harmonia axyridis on the reproduction and physiological status of Spodoptera frugiperda. We observed that, even in the absence of predation, the mere presence of H. axyridis led to a reduction in the number of eggs laid by S. frugiperda adults. This reduction was attributed to the induction of stress responses in S. frugiperda, characterized by inflammatory reactions and increased levels of antioxidant enzymes. Alterations in energy allocation occurred, resulting in decreased allocation towards hormone production and vitellogenin synthesis, ultimately leading to diminished fecundity. Our findings underscore the intricate mechanisms through which predators can impact pest populations within agricultural ecosystems. An increasing body of research has underscored the significant impact of non-consumptive effects on the dynamics of prey pests, encompassing growth, development, reproduction, and metabolism across various vertebrate and invertebrate taxa, rivaling the influence of consumption effects. In our investigation, we delved into the non-consumptive effects exerted by the natural predatory enemy Harmonia axyridis on the reproductive capacity and metabolism of Spodoptera frugiperda adults. Our findings revealed a substantial decrease in the reproductive ability of S. frugiperda adults when exposed to the non-consumptive effects of H. axyridis. Concurrently, we observed an elevation in hydrogen peroxide (H₂O₂) content and the activities of antioxidant enzymes such as superoxide dismutases (SODs), catalases (CATs), and peroxidases (PODs). Furthermore, notable alterations were detected in energy metabolism, characterized by heightened triglyceride levels and diminished glycogen and trehalose concentrations. These outcomes underscored the adaptive response of the pest aimed at mitigating non-consumptive adverse effects by augmenting antioxidant enzyme activity to counteract oxidative stress and minimize cellular damage. Nonetheless, this defensive mechanism entails a significant expenditure of energy resources, resulting in shifts in energy utilization. Elevated triglyceride levels and reduced glycogen and trehalose concentrations diminish available resources for reproductive processes, such as egg laying, ultimately culminating in decreased fecundity. This study contributes novel insights into the non-consumptive effects observed in insects, while also furnishing valuable insights into the mechanisms underlying insect stress responses. [ABSTRACT FROM AUTHOR]