Increased acetylcholinesterase inhibitor sensitivity as an intergenerational response to short-term acetylcholinesterase inhibitor exposure in Scapholeberis kingi
To determine the potential long-term risks associated with continual use of pesticides, we investigated (1) whether short-term exposure (48 h) of first generation (1G) Scapholeberis kingi to two acetylcholinesterase-inhibitor insecticides, pyraclofos and pirimicarb, would alter acetylcholinesterase-inhibitor sensitivity (based on immobility) in the second generation (2G), (2) whether acetylcholinesterase (AChE) activity-levels could be related to any observed change in sensitivity, and (3) whether intrinsic growth rates (r) in field cladocerans could vary between generations. We collected field-clone populations of different sensitivities from four sites in an agricultural area. Neonates (< 24 h old) were selected after insecticidal exposure for 48 h, then cultured without insecticide to obtain second-generation neonates. Based on the 48 h EC50 values, 2G neonates in the majority of the selected clones were more sensitive to the insecticides compared to the control groups. Changes in sensitivity could not be explained by AChE activity in the 2G. Although the r values decreased in few selected clones, these values recovered in the 2G suggesting that they could rapidly adapt to insecticidal exposure at the population level. The findings from our study can contribute to a better understanding in the potential risks of insecticides to aquatic organisms.
KeywordsCladocera Insecticide Acetylcholinesterase Multi-generational studies Field population
We thank Professor Yuichi Miyabara from Shinshu University for measuring the TOC and ion concentrations in the water samples. We thank Yusuke Oda from Shinshu University for providing information about the medrc package. We thank Professors Risako Tajiki-Nishino and Tomoki Fukuyama for giving advice on AChE activity analysis in cladocerans. We thank our technical staff, Aya Kitahara, for her support. Furthermore, we thank Professor Kazutoshi Ohyama for the opportunity to conduct this study. We would like to thank Editage (https://www.editage.jp) for English language editing. The experiments performed comply with the current laws of the country.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
Research involving animals
All procedures performed in studies involving animals were in accordance with the ethical standards of the institution. This article does not contain any studies with human participants or vertebrates performed by any of the authors.
Informed consent was not required for this study.
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