Dados do Trabalho

Título

Effects of Metarhizium anisopliae propagules on the digestive system of Aedes aegypti larvae, and viability of fungi exposed to gut lytic factors

Introdução

Vector management methods encompass direct control of the target population mainly by the use of insecticides. However, continuous employment of such substances may promote undesirable effects, especially in anthropophilic insects. Metarhizium anisopliae (brunneum) is an entomopathogenic fungi widely used as a sustainable mycoinsecticide in agriculture. Aedes aegypti larvae are detritivore and ingest particles, and the ingestion of fungal propagules is the main form of infection in culicidean larvae.

Objetivo(s)

The aim of this study is to characterize the enzymatic profile of Ae. aegypti larvae treated with forms of M. anisopliae, in order to identify physiological targets for optimization of biological control tools. In addition, we aim to clarify if larvae can counteract the conidia infection by synthesis of lytic factors.

Material e Métodos

Ae. aegypti larvae were exposed to 108 propagules/mL of conidia and blastospores formulated in 0.1% (v/v) Tween 80. β-glucosidase and β 1,3-glucanase activity were analysed from dissected intestine and rest of body of individual larvae samples. For β-glucosidase assays, homogenates were incubated with β-D-glucopyranoside (100 µM) and enzyme activity was measured by fluorimetry. For β-1,3-glucanase assays, pools of samples from 5-10 insects were incubated with laminarin (0,25 mg/µL) and the colorimetric of reduction sugars were measured by spectrofometry. Conidial viability was estimated by resazurin assay after exposure of a propagule suspension to carcass and intestine pool extracts.

Resultados e Conclusão

Conidia and blastospores decreased the activity of β-glucosidase in the gut after one post treatment in comparison to control groups. However, at the fifth day post treatment, conidia seemed to increase activity, while blastospores reduce it in larvae gut. Although no statistical differences were detected in β 1,3-glucanase assays, a tendency of increased enzymatic activity were detected at first and third day after treatment only in the rest of body in both treatments. Resazurin assays showed relevant decrease of conidial viability exposed to larval gut and rest of body extracts, in comparison to control groups. Preliminarily, we suggest that fungi propagules can modulate enzymatic activity in the digestive system of Ae. aegypti larvae. Additionally, insect´s lytic factors may interfere with the entomopathogen’s viability, demonstrating biochemical interactions and limitations of such host-pathogen interface.

Palavras-chave

Vector management, biological insecticide, biochemistry

Área

Eixo 04 | Entomologia / Controle de Vetores