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HISTOPATHOLOGICAL AND ULTRASTRUCTURAL EFFECTS OF D-ENDOTOXINS OF BACILLUS THURINGIENSIS SEROVAR ISRAELENSIS IN THE MIDGUT OF SIMULIUM PERTINAX LARVAE (DIPTERA, SIMULIIDAE)
Simulium pertinax
Midgut
Histopathology
Ultrastructure
Affilliation
Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Departamento de Bacteriologia. Rio de Janeiro, RJ, Brasil.
Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Departamento de Virologia. Rio de Janeiro, RJ, Brasil.
Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Departamento de Virologia. Rio de Janeiro, RJ, Brasil.
Secretaria de Saúde do. Estado de São Paulo. Superintendência de Controle de Endemias. São Paulo, SP, Brasil.
Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Departamento de Bacteriologia. Rio de Janeiro, RJ, Brasil.
Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Departamento de Virologia. Rio de Janeiro, RJ, Brasil.
Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Departamento de Virologia. Rio de Janeiro, RJ, Brasil.
Secretaria de Saúde do. Estado de São Paulo. Superintendência de Controle de Endemias. São Paulo, SP, Brasil.
Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Departamento de Bacteriologia. Rio de Janeiro, RJ, Brasil.
Abstract
The bacterium Bacillus thuringiensis (Bt) produces parasporal crystals containing δ-endotoxins responsible for
selective insecticidal activity on larvae. Upon ingestion, these crystals are solubilized in the midgut lumen and
converted into active toxins that bind to receptors present on the microvilli causing serious damage to the epithelial
columnar cells. We investigated the effect of these endotoxins on larvae of the Simulium pertinax, a common black fly
in Brazil, using several concentrations during 4 h of the serovar israelensis strain IPS-82 (LFB-FIOCRUZ 584),
serotype H-14 type strain of the Institute Pasteur, Paris. Light and electron microscope observations revealed, by
time and endotoxin concentration, increasing damages of the larvae midgut epithelium. The most characteristic
effects were midgut columnar cell vacuolization, microvilli damages, epithelium cell contents passing into the
midgut lumen and finally the cell death. This article is the first report of the histopathological effects of the Bti
endotoxins in the midgut of S. pertinax larvae and the data obtained may contribute to a better understanding of the
mode of action of this bacterial strain used as bioinsecticide against black fly larvae.
Keywords
Bacillus thuringiensis serovar israelensisSimulium pertinax
Midgut
Histopathology
Ultrastructure
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