Enzyme activity modification in adult beetles (Agelastica coerulea) inhabiting birch trees in an ozone-enriched atmosphere

Abstract

Tropospheric ozone (O 3) is a naturally occurring gas in the atmosphere. However, the concentration of O 3 increased in the 20 th century. Although the effects of O 3 on vegetation have been extensively studied since the 1950s, limited information exists regarding the effects of O 3 on insect herbivores. In particular, evidence is lacking regarding the effects of O 3 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 O 3 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 O 3 for 23 days. After 2 collection, the enzyme activities in the beetles were measured. Elevated O 3 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 O 3 biomarker systems in this beetle species. This adaptive response of the beetle, which was induced by moderate O 3 exposure, should be further tested across generations and for its protection against greater exposure.

Leaf defense capacity of Japanese elm (Ulmus davidiana var. japonica) seedlings subjected to a nitrogen loading and insect herbivore dynamics in a free air ozone-enriched environment

“…In fact, an analysis of the results of over 200 published studies suggested that leaf feeders can perform better on host plants that are stressed than on plants that are nonstressed, in support to the plant vigor hypothesis (Galway et al, 2004). In agreement to these, adult beetles of a different species (Agelastica coerulea) inhabiting birch trees in this FACE system were found to have higher activities of total antioxidants and lower detoxifying hydrolase such as α-and β-esterases in EOZ than in AOZ, although direct EOZ impacts on insects and indirect effects via plants cannot be separated (ElEla et al, 2018). Similarly to O3, leaf number with oviposited eggs was not affected by N despite there was a lower number of insects on N50 plants than on N0 plants on 20 July and September 19.…”

“…These may relate to changing insect damages induced by environmental changes (Santini et al 2004;Santini and Faccoli 2015), especially N deposition and O3 that can change plant-insect interaction and consequently contribute in the decline of forest trees (Koike et al 2013;Koike 2016). Only three studies have evaluated the leaf defense capacity of Japanese trees in relation to insect dynamics in free-air O3-concentration enrichment (FACE) systems (Sakikawa et al 2016;Agathokleous et al 2017a;ElEla et al 2018), and none of them concerns Japanese elm, despite previous researches have reported that grazing activities of elm leaf beetles was increased by elevated O3 (Richard et al 1988;Barger et al 1992).…”

Does Ozone Alter the Attractiveness of Japanese White Birch Leaves to the Leaf Beetle Agelastica coerulea via Changes in Biogenic Volatile Organic Compounds (BVOCs): An Examination with the Y-Tube Test

“…White birch, a common species in forests and often grown as boulevard in cities of Hokkaido in Japan [10,11,13], has heterophyllous leaves known as early and late leaves. Early leaves expand from the beginning of May, while late leaves start to develop after complete expansion of early leaves from around mid-July in northern Japan [24].…”

“…Damages by herbivores are responsible for losses of net primary production up to 15% in temperate forests [8]; however, herbivory can be altered by atmospheric contaminants. For example, we have previously found that insect herbivores systematically grazed leaves of different tree species in ambient O 3 plots more than in elevated O 3 plots of a free-air O 3 -concentration enrichment (FACE) system [10][11][12]. However, even if, in that situation, the leaves in the elevated O 3 condition had lower chemical defense capacities [12,13], leaves from the elevated O 3 conditions were often preferred by insects in choice laboratory assays [13].…”

“…Fuentes et al [23] concluded that the disruption of BVOCs because of reaction with O 3 was responsible for the decreasing attractiveness of BVOCs to the beetles. The phenomenon that insects graze less in elevated O 3 [11,13] was especially found in a system with alder leaf beetle Agelastica coerulea Baly (Coleoptera: Chrysomelidae) and Japanese white birch (Betula platyphylla var. japonica Hara; hereafter, white birch).…”