Imidacloprid modifies the mitotic kinetics and causes both aneugenic and clastogenic effects in the macrophyte Bidens laevis L.

Germán Lukaszewicz,Fernando G Iturburu,Daniela S Garanzini,Mirta L Menone,Stephan Pflugmacher

doi:10.1016/j.heliyon.2019.e02118

Abstract

Imidacloprid (IMI) is a neonicotinoid insecticide widely used in agricultural activities all around the world. This compound is transported from croplands to surrounding freshwater ecosystems, producing adverse effects on non-target organisms. Because of the relevance of aquatic macrophytes in the above-mentioned environments and the lack of studies of potential effects of IMI on them, this work aimed to assess the mitotic process and potential genotoxicity in the aquatic macrophyte Bidens laevis L. Although the analysis of the Mitotic Index (MI) showed that IMI was not cytotoxic, the Cell Proliferation Kinetics (CPK) frequencies evidenced modifications in the kinetics of the mitotic process. Indeed, the anaphases ratio decreased at 10 and 100 μg/L IMI, while at 1000 μg/L an increase of prophases ratio and a decrease of metaphases ratio were observed. Regarding genotoxicity, IMI produced an increase of the abnormal metaphases frequency from 10 μg/L to 1000 μg/L as well as an increase in clastogenic anaphases-telophases frequency at 100 and 1000 μg/L. In addition, aneugenic anaphases-telophases and C-mitosis frequencies also increased at 1000 μg/L, confirming the effects on the mitotic spindle. Considering the genotoxic effects on B. laevis through two different mechanisms (aneugenic and clastogenic) and the wide spread use of IMI in agriculture, these mechanisms of toxicity on macrophytes should be considered among other recognized effects of this insecticide on aquatic biota.

Highlights

Among current use pesticides, neonicotinoids chemical group sales grew the most in recent years (Elbert et al, 2008)
Leaves of B. laevis showed no changes on chlorophyll a and a/b ratio with respect to control (p > 0.05), an increase of chlorophyll b and total chlorophyll content were detected at 1000 and 1 and 1000 μg/L IMI, respectively (p < 0.05, Table 1)
A 24 h exposure to the recognized genotoxic compound MMS produced a significant increase of aneugenic, clastogenic and total chromosome aberrations in anaphase–telophase (CAAT) figures (3, 19 and 3.5-fold, respectively; p < 0.05, Fig. 1) as well as an increase in the frequency of abnormal metaphases

Summary

Introduction

Neonicotinoids chemical group sales grew the most in recent years (Elbert et al, 2008). Their chemical properties (mainly their hydrophilicity) allow systemic protection of crops, leading to new modes of application, i.e. seed coating (Bonmatin et al, 2015). This hydrophilicity let them reach water bodies by runoff or lixiviation events (Miles et al, 2017). Imidacloprid (IMI) was the first launched neonicotinoid and nowadays it is the best-selling insecticide in the world. For a complete review of neonicotinoids in surface water please see Morrissey et al (2015)

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