Gene expression in bumble bee larvae differs qualitatively between high and low concentration imidacloprid exposure levels

Abstract

Neonicotinoid pesticides negatively impact bumble bee health, even at sublethal concentrations. Responses to the neonicotinoid imidacloprid have been studied largely at individual adult and colony levels, focusing mostly on behavioral and physiological effects. Data from developing larvae, whose health is critical for colony success, are deficient, particularly at the molecular level where transcriptomes can reveal disruption of fundamental biological pathways. We investigated gene expression of Bombus impatiens larvae exposed through food provisions to two field-realistic imidacloprid concentrations (0.7 and 7.0 ppb). We hypothesized both concentrations would alter gene expression, but the higher concentration would have greater qualitative and quantitative effects. We found 678 genes differentially expressed under both imidacloprid exposures relative to controls, including mitochondrial activity, development, and DNA replication genes. However, more genes were differentially expressed with higher imidacloprid exposure; uniquely differentially expressed genes included starvation response and cuticle genes. The former may partially result from reduced pollen use, monitored to verify food provision use and provide additional context to results. A smaller differentially expressed set only in lower concentration larvae, included neural development and cell growth genes. Our findings show varying molecular consequences under different field-realistic neonicotinoid concentrations, and that even low concentrations may affect fundamental biological processes.

Imidacloprid disrupts larval molting regulation and nutrient energy metabolism, causing developmental delay in honey bee Apis mellifera

“…A recent study using next-generation sequencing has indicated that sublethal imidacloprid treatment during the larval stage causes changes in gene expression in larvae, pupae, and adults, suggesting a persistent sublethal impact on honey bee development ( Chen et al, 2021 ). Furthermore, a latest study has demonstrated that imidacloprid induces differential gene expression in bumble bee larvae, resulting in unique expression patterns related to various biological processes such as starvation response, cuticle genes, neural development, and cell growth ( Martín-Blázquez et al, 2023 ).…”

A New Approach for Detecting Sublethal Effects of Neonicotinoids on Bumblebees Using Optical Sensor Technology

“…The field-realistic concentration of imidacloprid found in nectar is 10 ppb [ 33 , 34 ] which means that, given the fact that a bumblebee worker consumes in a full day 150–300 μL of nectar, a worker ingests 1,5–3 ng of imidacloprid/day [ 35 ]. The findings of these studies show that exposure to field-realistic concentrations of neonicotinoids can impair their physiology [ 36 , 37 , 38 ], behaviour [ 20 , 35 , 37 , 39 , 40 , 41 , 42 ], and colony survival [ 22 , 43 , 44 , 45 ]. Among all of these studies, there are some that focus on the sublethal effects of field-realistic concentration of neonicotinoids on bumblebee flight and forage activity.…”