Searching beyond the streetlight: Neonicotinoid exposure alters the neurogenomic state of worker honey bees

Abstract

Neonicotinoid insecticides have been implicated in honey bee declines, with many studies showing that sublethal exposure impacts bee behaviors such as foraging, learning, and memory. Despite the large number of ecotoxicological studies carried out to date, most focus on a handful of worker phenotypes leading to a “streetlight effect” where the a priori choice of phenotypes to measure may influence the results and conclusions arising from the studies. This bias can be overcome with the use of toxicological transcriptomics, where changes in gene expression can provide a more objective view of how pesticides alter animal traits. Here, we used RNA sequencing to examine the changes in neurogenomic states of nurse and forager honey bees that were naturally exposed to neonicotinoids in the field and artificially exposed to neonicotinoids in a controlled experiment. We found that neonicotinoid exposure influenced the neurogenomic state of foragers and nurses in different ways; foragers experienced shifts in expression of genes involved in cognition and development, while nurses experienced shifts in expression of genes involved in metabolism. Our study suggests that neonicotinoids influence nurse and forager bees in a different manner. We also found no to minimal overlap in the differentially expressed genes in our study and in previously published studies, which might help reconcile the seemingly contradictory results often reported in the neonicotinoid literature.

Potential Risk of Residues From Neonicotinoid‐Treated Sugar Beet in Flowering Weeds to Honey Bees (Apis mellifera L.)

“…Hence Harwood and Dolezal (2020) suggest that honey bees may be resilient to pesticide stress, and therefore their responses may be context dependent. This leads to the conclusion that effects of insecticides and other pesticides assessed under laboratory conditions may not show their true potential under colony conditions (Tsvetkov & Zayed, 2021). For wild bees, on the other hand, this scenario could be different (Rundlöf et al, 2015).…”

Pesticide risk assessment: honeybee workers are not all equal regarding the risk posed by exposure to pesticides

“…Lastly, given that the impact of pesticides depends not only on the fate of the molecule in the body, but also on its interaction with the biological target and consecutive effects on the organism, we could also expect that sulfoxaflor affected nurses and foragers in different manners. A recent study demonstrated that nurse and forager bees were affected in different ways by neonicotinoids at the gene expression level in the brain: while the expression of genes involved in cognition and development was predominantly affected in foragers, the expression of genes involved in metabolism was modified in nurses (Tsvetkov and Zayed 2021). Although, it is not known how such effects might affect honeybee survival or performance, it could help to explain differences in pesticide sensitivity.…”

Characterization of the Metabolites of Neonicotinoid Insecticide Imidaclothiz in Mice

“…Desnitro-imidacloprid exhibits significantly greater mammalian toxicity than imidacloprid . In addition, neonicotinoids threaten the well-being of bees, aquatic organisms, birds, and mammals. − It is known that imidaclothiz can induce oxidative stress and damage to nontarget earthworms . Whether the degradation products of imidaclothiz pose a risk to nontarget organisms is unknown.…”