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| Author(s): |
Marilucia Santorum
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Botucatu. 2019-07-04. |
| Institution: | Universidade Estadual Paulista (Unesp). Instituto de Biociências. Botucatu |
| Defense date: | 2019-05-15 |
| Advisor: | Daniela Carvalho dos Santos |
| Abstract | |
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. (AU) | |
| FAPESP's process: | 15/07119-9 - Toxicity evaluation of the insecticide Novaluron in Bombyx mori (Lepidoptera: Bombycidae) |
| Grantee: | Marilucia Santorum |
| Support Opportunities: | Scholarships in Brazil - Doctorate |