Sub-Lethal Peak Exposure to Insecticides Triggers Olfaction-Mediated Avoidance in Zebrafish Larvae

Abstract

In agricultural areas, insecticides inevitably reach water bodies via leaching or run-off. While designed to be neurotoxic to insects, insecticides have adverse effects on a multitude of organisms due to the high conservation of the nervous system among phyla. To estimate the ecological effects of insecticides, it is important to investigate their impact on non-target organisms such as fish. Using zebrafish as the model, we investigated how different classes of insecticides influence fish behavior and uncovered neuronal underpinnings of the associated behavioral changes, providing an unprecedented insight into the perception of these chemicals by fish. We observed that zebrafish larvae avoid diazinon and imidacloprid while showing no response to other insecticides with the same mode of action. Moreover, ablation of olfaction abolished the aversive responses, indicating that fish smelled the insecticides. Assessment of neuronal activity in 289 brain regions showed that hypothalamic areas involved in stress response were among the regions with the largest changes, indicating that the observed behavioral response resembles reactions to stimuli that threaten homeostasis, such as changes in water chemistry. Our results contribute to the understanding of the environmental impact of insecticide exposure and can help refine acute toxicity assessment.

Zebrafish Larvae Rapidly Recover from Locomotor Effects and Neuromuscular Alterations Induced by Cholinergic Insecticides

“…In order to do so, sample triplicates were analyzed on the first day and the last day of exposure. The detailed method is described by Könemann et al (2021) . Briefly, samples were separated using LC on a C18 Nucleodur column and measured using a Quadrupole Orbitrap mass spectrometer (Q Exactive Plus, Thermo Fisher Scientific Inc., USA) with electrospray ionization in a positive ion mode.…”

Sublethal Exposure to Cadmium Induces Chemosensory Dysfunction in Fire Ants

“…Cu-exposed zebrafish exhibited different microRNA (miRNA) expression profiles in a dose–response manner, and these deregulated miRNAs may be involved in neurogenesis . To date, numerous studies have confirmed the association between chemosensory dysfunction and environmental contaminants. − However, the potential mechanisms underlying the effects of contaminants on the chemosensory process remain poorly understood …”

“… 20 To date, numerous studies have confirmed the association between chemosensory dysfunction and environmental contaminants. 21 − 23 However, the potential mechanisms underlying the effects of contaminants on the chemosensory process remain poorly understood. 15 …”

Addressing chemical pollution in biodiversity research

“…In juvenile Coho salmon, low levels of copper also increased the fish's vulnerability to predators, but via a different mechanism, namely by decreasing its ability to detect and respond to chemosensory cues indicating predator presence (McIntyre et al, 2012). Zebrafish larvae were shown to smell the presence of certain insecticides in water and actively avoid contaminated areas, raising the question of whether chemicals can affect fish migratory behaviour as a result (Könemann et al, 2021). Similar effects can be expected to unfold in other animal species as well.…”