An approach to choose the most relevant time of exposure for biomarker measurement in earthworms exposed to pesticides

Biomarker measurements on organisms known as bioindicators are considered as good tools to assess both environmental quality and functioning. Earthworms, by their ecological functions and sensitivity, are relevant organisms to evaluate the quality of soils disturbed by human activities. Despite a great amount of experiments intended to study xenobiotics effects on the physiology of soil organisms under controlled conditions, no clear trend emerged concerning the responses of biomarkers. Owing to the high heterogeneity observed in laboratory protocols (species used as models, types and concentrations of contaminants, time of exposure, analysis methods) can even lead to contradictory results. The aim of this study was to underline the kinetic responses of biomarkers involved in earthworm physiology (defense against oxidative stress, detoxification mechanisms and energy reserves) within time. Our main hypothesis was that the conditions and particularly the time of exposure strongly influenced the results obtained in these studies. Here we provide the most relevant interval of time exposure for each biomarker. Earthworms of the species Aporrectodea icterica were exposed to pesticides in laboratory conditions, at realistic agronomic dose or agronomic dose x 10, alone or in a mixture. Earthworms were placed in microcosms containing contaminated soil, during periods of 2, 4, 7, 10, 14 and 21 days before biomarkers analysis. The two selected pesticide were an insecticide of the pyrethrinoids family, CYTHRINE MAX ® (Cypermethrin) and a fungicide of the strobilurin family, AMISTAR ® (Azoxystrobin), commonly applied in cereal crops. We will present the results of the kinetic responses for each selected biomarkers (catalase, glutathione-S-transferase, superoxide dismutase, proteins …), time of exposure and pesticide dose within time. We will also identify the most suitable period to their measurement