Exposure to thiamethoxam during the larval phase affects synapsin levels in the brain of the honey bee

• Published in: Ecotoxicology and environmental safety 2019-03, Vol.169, p.523-528
• Main Authors: Tavares, Daiana Antonia, Roat, Thaisa Cristina, Silva-Zacarin, Elaine Cristina Mathias, Nocelli, Roberta Cornélio Ferreira, Malaspina, Osmar
• Format: Article
• Language: English
• Subjects: Animals; Apis mellifera; Bees - drug effects; Bees - growth & development; Bees - metabolism; Brain - drug effects; Brain - metabolism; Brain - ultrastructure; Honey bee development; Insecticides - analysis; Insecticides - toxicity; Larva - drug effects; Larva - metabolism; Neonicotinoids; Pesticide, mushroom body, antennal lobe; Pollen - chemistry; Pupa - drug effects; Pupa - metabolism; Synapsins - metabolism; Thiamethoxam - analysis; Thiamethoxam - toxicity
• ISSN: 0147-6513; 1090-2414
• DOI: 10.1016/j.ecoenv.2018.11.048

Thiamethoxam (TMX) is a neurotoxic insecticide widely used for insect pest control. TMX and other neonicotinoids are reported to be potential causes of honey bee decline. Due to its systematic action, TMX may be recovered in pollen, bee bread, nectar, and honey, which make bees likely to be exposed to contaminated diet. In this study, we used immunolabeling to demonstrate that sublethal concentrations of TMX decrease the protein levels of synapsin in the mushroom bodies (MBs) and the antennal lobes (ALs) of pupae and newly emerged worker bees that were exposed through the food to TMX during the larval phase. A decrease in the synapsin level was observed in the MBs of pupae previously exposed to 0.001 and 1.44 ng/µL and in newly emerged bees previously exposed to 1.44 ng/µL and no changes were observed in the optical lobes (OLs). In the ALs, the decrease was observed in pupae and newly emerged bees exposed to 1.44 ng/µL. Because the MBs and ALs are brain structures involved in stimuli reception, learning, and memory consolidation and because synapsin is important for the regulation of neurotransmitter release, we hypothesize that exposure to sublethal concentrations of TMX during the larval stage may cause neurophysiological disorders in honey bees. [Display omitted] •Larvae contaminated with thiamethoxam have brain damage in their development.•Thiamethoxam reduced synapsin level in mushroom bodies and antennal lobes.•The alterations on brain may cause damage in the pupae and newly emerged neurophysiology.