Maximizing crop yields relies on the use of agrochemicals to control insect pests. One of the most widely used classes of insecticides are neonicotinoids that interfere with signalling of the ...neurotransmitter acetylcholine, but these can also disrupt crop-pollination services provided by bees. Here, we analysed whether chronic low dose long-term exposure to the neonicotinoid thiamethoxam alters gene expression and alternative splicing in brains of Africanized honey bees, Apis mellifera, as adaptation to altered neuronal signalling. We find differentially regulated genes that show concentration-dependent responses to thiamethoxam, but no changes in alternative splicing. Most differentially expressed genes have no annotated function but encode short Open Reading Frames, a characteristic feature of anti-microbial peptides. As this suggested that immune responses may be compromised by thiamethoxam exposure, we tested the impact of thiamethoxam on bee immunity by injecting bacteria. We show that intrinsically sub-lethal thiamethoxam exposure makes bees more vulnerable to normally non-pathogenic bacteria. Our findings imply a synergistic mechanism for the observed bee population declines that concern agriculturists, conservation ecologists and the public.
Nanotechnology has the potential to overcome the challenges of sustainable agriculture, and nanopesticides can control agricultural pests and increase farm productivity with little environmental ...impact. However, it is important to evaluate their toxicity on non-target organisms, such as honeybees (Apis mellifera) that forage on crops. The aims of this study were to develop a nanopesticide that was based on solid lipid nanoparticles (SLNs) loaded with pyrethrum extract (PYR) and evaluate its physicochemical properties and short-term toxicity on a non-target organism (honeybee). SLN + PYR was physicochemically stable after 120 days. SLN + PYR had a final diameter of 260.8 ± 3.7 nm and a polydispersion index of 0.15 ± 0.02 nm, in comparison with SLN alone that had a diameter of 406.7 ± 6.7 nm and a polydispersion index of 0.39 ± 0.12 nm. SLN + PYR had an encapsulation efficiency of 99%. The survival analysis of honeybees indicated that PYR10ng presented shorter longevity than those in the control group (P ≤ 0.01). Empty nanoparticles and PYR10ng caused morphological alterations in the bees’ midguts, whereas pyrethrum-loaded nanoparticles had no significant effect on digestive cells, so are considered safer, at least in the short term, for honeybees. These results are important in understanding the effects of nanopesticides on beneficial insects and may decrease the environmental impacts of pesticides.
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•Nanoparticles showed good properties to be used as pyrethrum carrier system.•Pyrethrum extract in nanocarrier and sublethal concentrations is safer for honeybees.•Pyrethrum and nanotechnology showed promising results aiming agriculture applications.
Fipronil is a phenylpyrazole insecticide that is widely used in Brazilian agriculture for pest control. Although honeybees are not targets of fipronil, studies indicate that this pesticide can be ...harmful to honeybees. To assess the effects of fipronil in the brain of Africanized
Apis mellifera
workers, this study focused on the toxico-proteome profiling of the brain of newly emerged and aged honeybee workers that were exposed to a sub-lethal dose (10 pg fipronil per day. i.e.
1
/
100
of LD
50
/bee/day during 5 days) of the insecticide. Proteomic analysis identified 25 proteins that were differentially up-regulated or down-regulated when the fipronil-exposed and non-exposed groups were compared. These proteins are potentially related to pathogen susceptibility, neuronal chemical stress, neuronal protein misfolding, and occurrence of apoptosis, ischemia, visual impairment, damaged synapse formation, brain degeneration, memory and learning impairment. The exposure of honeybees to a very low dose of fipronil, even for a short period of time (5 days), was sufficient to cause a series of important neuroproteomic changes in the brains of honeybees.
Neonicotinoids have been described as toxic to bees. In this context, the A. mellifera foragers were exposed to a sublethal concentration of thiamethoxam (LC50/100: 0,0227 ng de thiamethoxam/μL−1 ...diet), a neurotoxic insecticide, for 8 days; and it was decided to investigate the insecticide effect on the brain by a shotgun proteomic approach followed by label-free quantitative-based proteomics. A total of 401 proteins were identified in the control group (CG); and a total of 350 proteins in the thiamethoxam exposed group (TMX). Quantitative proteomics data showed up 251 proteins with significant quantitative values in the TMX group. These findings demonstrated the occurrence of shared and unique proteins with altered expression in the TMX group, such as ATP synthase subunit beta, heat shock protein cognate 4, spectrin beta chain-like, mushroom body large-type Kenyon cell-specific protein 1-like, tubulin alpha-1 chain-like, arginine kinase, epidermal growth factor receptor, odorant receptor, glutamine synthetase, glutamate receptor, and cytochrome P450 4c3. Meanwhile, the proteins that were expressed uniquely in the TMX group are involved mainly in the phosphorylation, cellular protein modification, and cell surface receptor signalling processes. Interaction network results showed that identified proteins are present in five different metabolic pathways - oxidative stress, cytoskeleton control, visual process, olfactory memory, and glutamate metabolism. Our scientific outcomes demonstrated that a sublethal concentration of thiamethoxam can impair biological processes and important metabolic pathways, causing damage to the nervous system of bees, and in the long term, can compromise the nutrition and physiology of individuals from the colony.
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•Neurotoxic insecticide affected the bee biological processes and metabolic pathways.•The exposed group to thiamethoxam presented altered expression proteins.•The altered proteins identified are involved in the nervous system of bees.•The data suggest intense brain activities in the exposed group to the insecticide.•Bees can suffer memory loss, olfactory and visual deficiencies.
Securing food supply for a growing population is a major challenge and heavily relies on the use of agrochemicals to maximize crop yield. It is increasingly recognized, that some neonicotinoid ...insecticides have a negative impact on non-target organisms, including important pollinators such as the European honeybee Apis mellifera. Toxicity of neonicotinoids may be enhanced through simultaneous exposure with additional pesticides, which could help explain, in part, the global decline of honeybee colonies. Here we examined whether exposure effects of the neonicotinoid thiamethoxam on bee viability are enhanced by the commonly used fungicide carbendazim and the herbicide glyphosate. We also analysed alternative splicing changes upon pesticide exposure in the honeybee. In particular, we examined transcripts of three genes: (i) the stress sensor gene X box binding protein-1 (Xbp1), (ii) the Down Syndrome Cell Adhesion Molecule (Dscam) gene and iii) the embryonic lethal/abnormal visual system (elav) gene, which are important for neuronal function. Our results showed that acute thiamethoxam exposure is not enhanced by carbendazim, nor glyphosate. Toxicity of the compounds did not trigger stress-induced, alternative splicing in the analysed mRNAs, thereby leaving dormant a cellular response pathway to these man-made environmental perturbations.
Exposure of A. mellifera workers to COâ has been reported to decrease life span, induce behavioral changes, and inhibit the development of some glands and the ovaries. However, the use of COâ is ...currently practiced among beekeepers and how the development of workersâ ovaries are affected is unknown. The present work aimed to evaluate the effect of COâ on the ovaries of A. mellifera workers, using a morphological approach. Newly emerged, and 3, 5, and 10-day-old workers were exposed to saturated COâ for 30 seconds, more than once. The ovaries were examined under light (LM) and transmission electron microscopy (TEM). The ovaries of narcotized, 5-day-old workers exhibited long ovarioles with well-developed germarium, although oogenesis showed little development. While in the control group, the ovaries already exhibited cysts with cystocytes forming rosettes. At 10-days-old, the ovaries feature was variable; some of the ovaries showed ovarioles with many rosette cysts while others showed a high intensity of disorganization due to the beginning of cell death. The ovarioles of the ovaries of 15-day-old treated workers were morphologically varied as oogenesis showed little or no advance. In others cases, a complete disorganization with swollen cells and cell death features were observed. Germ cells of the ovaries of COâ-treated workers exhibited well-structured organelles, such as the Golgi complex, and larger amounts of mitochondria in the cytoplasm than the control group, but there was disorganization of the endoplasmic reticulum membranes. Our findings revealed that the exposure of workers to COâ promotes impairment of oogenesis and ovarian degradation.
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