Single and mixed exposure to distinct groups of pesticides suggests endocrine disrupting properties of imidacloprid in zebrafish embryos

Abstract

Due to their selective toxicity to insects, nicotinoid compounds have been widely used to control pests in crops and livestock around the world. However, despite the advantages presented, much has been discussed about their harmful effects on exposed organisms, either directly or indirectly, with regards to endocrine disruption. This study aimed to evaluate the lethal and sublethal effects of imidacloprid (IMD) and abamectin (ABA) formulations, separately and combined, on zebrafish (Danio rerio) embryos at different developmental stages. For this, Fish Embryo Toxicity (FET) tests were carried out, exposing two hours post-fertilization (hpf) zebrafish to 96 hours of treatments with five different concentrations of abamectin (0.5–11.7 mg L⁻¹), imidacloprid (0.0001–1.0 mg L⁻¹), and imidacloprid/abamectin mixtures (LC₅₀/2 − LC₅₀/1000). The results showed that IMD and ABA caused toxic effects in zebrafish embryos. Significant effects were observed regarding egg coagulation, pericardial edema, and lack of larvae hatching. However, unlike ABA, the IMD dose-response curve for mortality had a bell curve display, where medium doses caused more mortality than higher and lower doses. These data demonstrate the toxic influence of sublethal IMD and ABA concentrations on zebrafish, suggesting that these compounds should be listed for river and reservoir water-quality monitoring.

Keywords:

• FET test
• neonicotinoid
• abamectin
• pesticides
• Danio rerio
• fish
• water quality
• toxic effects
• sublethal effects
• endocrine disruption

Acknowledgments

We would like to thank the former Director of the Biology Institute Dr. Antônio Batista Filho and Dr. Marcos Roberto Potenza (in memoriam) for their collaboration in carrying out this project and for the opportunity to carry out the doctoral dissertation of Scientific Researcher Magda Santiago.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The data supporting the results and analyses presented in this paper are in possession of the corresponding Author.

Additional information

Funding

This work was supported by Biological Institute and Hospital das Clínicas of the University of Sao Paulo.