Avaliação da toxicidade do inseticida novaluron em Bombyx mori (Lepidoptera: Bombycidae)
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Data
2019-05-15
Autores
Santorum, Marilucia
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Universidade Estadual Paulista (Unesp)
Resumo
O bicho-da-seda, Bombyx mori (Lepidoptera: Bombycidae), é o inseto de maior importância econômica na produção de seda. A lagarta se alimenta de folhas de amoreira e é altamente sensível a agrotóxicos, assim o uso destes em culturas agrícolas circunvizinhas às plantações de amoreira pode afetar o desenvolvimento de B. mori, acarretando em desequilíbrio nas suas funções metabólicas e, consequentemente, comprometendo a produção de casulos. Entre estes agrotóxicos, destaca-se o Novaluron, inseticida inibidor da síntese de quitina nos insetos e empregado no controle de insetos pragas de culturas agrícolas próximas as plantações de amoreira. Assim, investigamos os efeitos tóxicos de Novaluron no desenvolvimento de B. mori. Lagartas de B. mori, foram separadas em dois grupos experimentais: grupo controle (GC) e grupo tratamento (GT: tratado com 0, 15 mL/L de Novaluron). Após ecdise do 2° para o 3° instar, lagartas do GT foram alimentadas por 24 horas com folhas de amoreira tratadas com o inseticida. Paralelamente foi realizada uma nova exposição, porém em lagartas que realizavam a ecdise do 4° para o 5° instar. Lagartas, pupas e adultos de B. mori foram anestesiadas e segmentos do intestino médio, glândula da seda e órgãos reprodutores retirados e processados convencionalmente para técnicas de microscopias de luz, eletrônica e imunohistoquímica. Além disso, os efeitos no desenvolvimento, reprodução e qualidade do casulo também foram avaliados. O Novaluron provocou efeitos citotóxicos no intestino médio e na glândula da seda de lagartas de B. mori, bem como reprotoxicidade nos testículos e ovários de lagartas, pupas e adultos, através de pronunciadas alterações, como extrema rarefação citoplasmática e nuclear, dilatação do retículo endoplasmático, alteração mitocondrial, presença de vacúolos citoplasmáticos e dilatação celular com liberação de protusões citoplasmáticas, além de espaçamento entre células epiteliais e a lâmina basal e o desprendimento de algumas células para o lúmen. Em adição, destacamos vários sintomas de toxicidade de Novaluron em todas as fases do desenvolvimento de B. mori, tais como: grande taxa de mortalidade das lagartas, efeito negativo na qualidade do casulo produzido, redução no peso dos casulos construídos, construção de casulos defeituosos, além da significante redução no número de ovos ovipositados pelas fêmeas adultas de B. mori tratadas. Estes resultados nos mostram que Novaluron tem grande efeito tóxico em B. mori, afetando seu desenvolvimento, bem como a produção dos casulos da seda, o que pode causar sérios prejuízos à sericultura no Brasil.
The silkworm, Bombyx mori (Lepidoptera: Bombycidae is the insect of major economic importance in the production of silk. The larvae feeds on mulberry leaves and is highly sensitive to agrochemicals, thus the use of these in agricultural crops surrounding the mulberry plantations can affect the development of B. mori, causing an imbalance in its metabolic functions and, consequently, compromising the production of cocoons. Among these agrochemicals, stands out the Novaluron, an insecticide inhibitor of the synthesis of chitin in insects and used in the control of insect pests of crops near mulberry plantations. Thus, we investigated the lethal and sublethal effects of Novaluron on the development of B. mori. Larvae were selected into two experimental groups: control group (CG) and treatment group (TG: treated with 0, 15 mL/L Novaluron). After ecdysis from the 2nd to the 3rd instar, the TG larvae were fed for 24 hours with mulberry leaves treated with the insecticide. In parallel, a new exposition was carried out, however in larvae that carry out the ecdysis from the 4th to the 5th instar. B. mori larvae, pupae and adults were anesthetized and segments of the midgut, silk gland and reproductive organs were removed and processed conventionally for light microscopy, electron microscopy and immunohistochemistry. In addition, the effects on the development, reproduction and quality of the cocoon were also evaluated. Novaluron caused cytotoxic effects on the midgut and the silk gland of B. mori larvae, as well as reprotoxicity on the testes and ovaries of larvae, pupae and adults, through pronounced alterations such as extreme cytoplasmic and nuclear rarefaction, endoplasmic reticulum dilatation, mitochondrial alteration, presence of cytoplasmic vacuoles and cell dilatation with release of cytoplasmic protrusions, as well as spacing between epithelial cells and the basal lamina and the detachment of some cells into the lumen. In addition, we highlight several symptoms of Novaluron toxicity in all stages of the development of B. mori, such as: great mortality of larvae, negative effect on the quality of the cocoon produced, reduction in the weight of the cocoons constructed, construction of defective cocoons, besides the significant reduction in the number of eggs deposited by adult B. mori females treated. These results show that Novaluron has a great toxic effect on B. mori, affecting its development, as well as the production of the silk cocoons, which can cause serious damages to sericulture in Brazil.
The silkworm, Bombyx mori (Lepidoptera: Bombycidae is the insect of major economic importance in the production of silk. The larvae feeds on mulberry leaves and is highly sensitive to agrochemicals, thus the use of these in agricultural crops surrounding the mulberry plantations can affect the development of B. mori, causing an imbalance in its metabolic functions and, consequently, compromising the production of cocoons. Among these agrochemicals, stands out the Novaluron, an insecticide inhibitor of the synthesis of chitin in insects and used in the control of insect pests of crops near mulberry plantations. Thus, we investigated the lethal and sublethal effects of Novaluron on the development of B. mori. Larvae were selected into two experimental groups: control group (CG) and treatment group (TG: treated with 0, 15 mL/L Novaluron). After ecdysis from the 2nd to the 3rd instar, the TG larvae were fed for 24 hours with mulberry leaves treated with the insecticide. In parallel, a new exposition was carried out, however in larvae that carry out the ecdysis from the 4th to the 5th instar. B. mori larvae, pupae and adults were anesthetized and segments of the midgut, silk gland and reproductive organs were removed and processed conventionally for light microscopy, electron microscopy and immunohistochemistry. In addition, the effects on the development, reproduction and quality of the cocoon were also evaluated. Novaluron caused cytotoxic effects on the midgut and the silk gland of B. mori larvae, as well as reprotoxicity on the testes and ovaries of larvae, pupae and adults, through pronounced alterations such as extreme cytoplasmic and nuclear rarefaction, endoplasmic reticulum dilatation, mitochondrial alteration, presence of cytoplasmic vacuoles and cell dilatation with release of cytoplasmic protrusions, as well as spacing between epithelial cells and the basal lamina and the detachment of some cells into the lumen. In addition, we highlight several symptoms of Novaluron toxicity in all stages of the development of B. mori, such as: great mortality of larvae, negative effect on the quality of the cocoon produced, reduction in the weight of the cocoons constructed, construction of defective cocoons, besides the significant reduction in the number of eggs deposited by adult B. mori females treated. These results show that Novaluron has a great toxic effect on B. mori, affecting its development, as well as the production of the silk cocoons, which can cause serious damages to sericulture in Brazil.
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Palavras-chave
Bicho-da-seda, ultraestrutura, Novaluron, toxicidade, sintomatologia, silkworm, ultrastructure, toxicity, symptomatology