Stress indicator gene expression profiles, colony dynamics and tissue development of honey bees exposed to sub-lethal doses of imidacloprid in laboratory and field experiments.

Lina De Smet,Pavlos Ioannidis,Guy Smagghe,Dirk C De Graaf,Ivan Meeus,Karel Schoonvaere,Anna Hamamtzoglou,Frédéric Francis,Fani Hatjina,Dean E Riechers

doi:10.1371/journal.pone.0171529

Lina De Smet, Pavlos Ioannidis + Show 8 more

Open Access

https://doi.org/10.1371/journal.pone.0171529

Copy DOI

Abstract

In this study, different context-dependent effects of imidacloprid exposure on the honey bee response were studied. Honey bees were exposed to different concentrations of imidacloprid during a time period of 40 days. Next to these variables, a laboratory-field comparison was conducted. The influence of the chronic exposure on gene expression levels was determined using an in-house developed microarray targeting different immunity-related and detoxification genes to determine stress-related gene expression changes. Increased levels of the detoxification genes encoding, CYP9Q3 and CYT P450, were detected in imidacloprid-exposed honey bees. The different context-dependent effects of imidacloprid exposure on honey bees were confirmed physiologically by decreased hypopharyngeal gland sizes. Honey bees exposed to imidacloprid in laboratory cages showed a general immunosuppression and no detoxification mechanisms were triggered significantly, while honey bees in-field showed a resilient response with an immune stimulation at later time points. However, the treated colonies had a brood and population decline tendency after the first brood cycle in the field. In conclusion, this study highlighted the different context-dependent effects of imidacloprid exposure on the honey bee response. These findings warn for possible pitfalls concerning the generalization of results based on specific experiments with short exposure times. The increased levels of CYT P450 and CYP9Q3 combined with an immune response reaction can be used as markers for bees which are exposed to pesticides in the field.

Highlights

Imidacloprid is a neurotoxic insecticide that acts on the nicotinergic acetylcholine receptors of the central nervous system of insects and belongs to the class of chemicals called neonicotinoids [1]
The latter show a high insecticidal activity and are used against a broad range of agricultural pests. Because of their activity against non-target organisms among which pollinating insects, bees in particular, these insecticides are the subjects of debate in Europe and beyond
The dynamics of a honey bee colony is the result of a wide range of physiological and behavioural changes such as development of brood and population over time

Summary

Introduction

Imidacloprid is a neurotoxic insecticide that acts on the nicotinergic acetylcholine receptors of the central nervous system of insects and belongs to the class of chemicals called neonicotinoids [1] The latter show a high insecticidal activity and are used against a broad range of agricultural pests. The dynamics of a honey bee colony is the result of a wide range of physiological and behavioural changes such as development of brood and population over time. These variables are predictors for the ability of the colony to survive over winter and to reproduce [7, 8]. Development of HPGs starts very early in the life of the adult honey bees, and the glands reach their maximum size and weight when the honey bees are 8–12 days old [12]

Methods

Results

Conclusion