Alterações no cérebro e no ventrículo de abelhas Apis mellifera expostas ao imidacloprido
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Data
2016-07-25
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Universidade Estadual Paulista (Unesp)
Resumo
As abelhas Apis mellifera se destacam expressivamente no contexto econômico e ecológico pelos produtos apícolas fornecidos como própolis, geleia real, mel, cera e apitoxina, e pela extrema importância que o processo de polinização representa para o equilíbrio dos ecossistemas. Estudos atuais indicam que algumas substâncias sintéticas, utilizadas no controle de pragas na agricultura, podem estar envolvidas em casos de intoxicação de abelhas. Os efeitos desses produtos podem não ser imediatamente notados, mas podem causar sérios efeitos fisiológicos e comportamentais que acabam por comprometer a viabilidade da colônia, de uma maneira geral. Diante do exposto, este trabalho teve como objetivos principais: avaliar a toxicidade oral do imidacloprido para A. mellifera por meio da determinação da concentração letal média (CL50), e analisar os efeitos de uma concentração subletal (CL50/100) no intestino e no cérebro por meio de de microscopia eletrônica de transmissão, bem como na distribuição de proteínas no cérebro, por meio da técnica do MALDI-Imaging. O valor da CL50 estabelecido foi de 1,4651 ng imidacloprido/μL de dieta. A exposição à CL50/100 (0,0146 ng imidacloprido/μL alimento) causou alterações bastante significativas nas células do ventrículo, principalmente a partir do quarto dia de exposição, como redução do tamanho do núcleo, condensação cromatínica, alterações mitocondriais e aumento de vacúolos digestivos e citoplasmáticos. No cérebro, destacaram-se os danos mitocondriais, espaçamento entre as células, núcleos irregulares e dilatação do espaço perinuclear. Essa concentração subletal afetou também a distribuição espacial de diversas proteínas no cérebro de abelhas, envolvidas principalmente com processos de sinapses, suprimento de oxigênio, estresse químico e oxidativo, degeneração neuronal e aprendizado e memória, demonstrando que esse inseticida causa alterações bioquímicas que podem inviabilizar funções neuronais importantes.
The bees Apis mellifera stand out significantly in the economic and ecological context for products supplied as propolis, royal jelly, honey, beeswax and venom, and because the extreme importance that the pollination process is for the equilibrium of ecosystems. Current studies indicate that some synthetic substances used to control pests in agriculture may be involved in cases of intoxication of bees. The effects of these products may not be immediately noticeable, but they can cause serious physiological and behavioral effects that can compromise the viability of the colony. Given the above, this work had as main objectives: to evaluate the oral toxicity of imidacloprid to A. mellifera through the determination of the lethal concentration (LC50), and analyse the effects of a sublethal concentration (LC50/100) in the midgut and brain through transmission electron microscopy as well as the distribution of proteins in the brain, by MALDI-Imaging technique. The LC50 value established to imidacloprid was 1.4651 ng/μL diet. The exposure to LC50/100 (0.0146 ng imidacloprid/μL diet) caused quite significant alterations in ventricular cells, especially after the fourth day of exposure, such as reduction of the size of the nucleus, chromatin condensation, mitochondrial alterations and increased of digestive and cytoplasmic vacuoles. In the brain, it was possible to observe mitochondrial damages, spacing among cells, irregular nuclei and dilation in the perinuclear space. This sublethal concentration also affected the spatial distribution of several proteins in the brains of bees, mainly involved in synapse processes, oxygen supply, chemical and oxidative stress, neuronal degeneration, learning and memory, demonstrating that this insecticide cause biochemical changes that can derail important neuronal functions.
The bees Apis mellifera stand out significantly in the economic and ecological context for products supplied as propolis, royal jelly, honey, beeswax and venom, and because the extreme importance that the pollination process is for the equilibrium of ecosystems. Current studies indicate that some synthetic substances used to control pests in agriculture may be involved in cases of intoxication of bees. The effects of these products may not be immediately noticeable, but they can cause serious physiological and behavioral effects that can compromise the viability of the colony. Given the above, this work had as main objectives: to evaluate the oral toxicity of imidacloprid to A. mellifera through the determination of the lethal concentration (LC50), and analyse the effects of a sublethal concentration (LC50/100) in the midgut and brain through transmission electron microscopy as well as the distribution of proteins in the brain, by MALDI-Imaging technique. The LC50 value established to imidacloprid was 1.4651 ng/μL diet. The exposure to LC50/100 (0.0146 ng imidacloprid/μL diet) caused quite significant alterations in ventricular cells, especially after the fourth day of exposure, such as reduction of the size of the nucleus, chromatin condensation, mitochondrial alterations and increased of digestive and cytoplasmic vacuoles. In the brain, it was possible to observe mitochondrial damages, spacing among cells, irregular nuclei and dilation in the perinuclear space. This sublethal concentration also affected the spatial distribution of several proteins in the brains of bees, mainly involved in synapse processes, oxygen supply, chemical and oxidative stress, neuronal degeneration, learning and memory, demonstrating that this insecticide cause biochemical changes that can derail important neuronal functions.
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Inseticida, Toxicidade, Ultraestrutura, Espectrometria, Proteína, Insecticide, Toxicity, Ultrastructure, Spectrometry, Proteins