Tropospheric ozone (O3) is a naturally occurring gas in the atmosphere. However, the concentration of O3 increased in the twentieth century. Although the effects of O3 on vegetation have been extensively studied since the 1950s, limited information exists regarding the effects of O3 on insect herbivores. In particular, evidence is lacking regarding the effects of O3 on the biology of insect herbivores. Agelastica coerulea Baly (1874) is a coleopteran species that grazes on Betulaceae plants. In this study, to investigate the effects of O3 on A. coerulea biology for the first time, female adult insects were collected from Japanese white birch trees grown in a Free Air Controlled Exposure System (FACE) in Sapporo, Japan. These beetles inhabited trees exposed either to ambient or to elevated O3 for 23 days. After collection, the enzyme activities in the beetles were measured. Elevated O3 led to a greater total antioxidant activity and lower α- and β-esterase activities, a phenomenon that may suggest an increased resistance of the beetles to stress. Our results are further discussed with regard to biological and toxicological aspects. Collectively, our findings indicate that total antioxidants and α- and β-esterase activities can serve as effective O3 biomarker systems in this beetle species. This adaptive response of the beetle, which was induced by moderate O3 exposure, should be further tested across generations and for its protection against greater exposure.
Keywords: Adaptive response; Antioxidants; Beetle; Enzymes; Esterase; Hormesis; Insect; Ozone.