Bacillus thuringiensis para controle de Musca domestica: seleção de estirpes e avaliação do perfil de hemócitos em larvas
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2017-06-28
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Universidade Federal de Goiás
Resumo
Musca domestica is considered one of the most harmful pests to the egg industry due to
its high reproductive capacity and great potential of acting as a mechanical vector of
many pathogenicagens to the egg-laying hens. Currently, the society is interested in
alternative methods for pest control, once the constant and indiscriminate use of
chemical products has caused intoxication to humans and domestic animals. Also, the
irregular use of chemicals has selected resistant fly populations, accumulated chemical
residues in the environment and food, and eliminated insects important to the natural
control of flies. In order to develop alternative methods to control M. domestica, this
study investigated Bacillus thuringiensis strains able to act as promising biological
control agents. Twenty two strains of B. thuringiensis were tested in a screening assay
for selecting the most virulent ones; one third of them were virulent to M. domestica
larva, and two of them were selected for the next tests. Bioassays were conducted with
the strains S601 and S599 to determine the larval treatment efficiency; they showed
efficiency to control larva of M. domestica in all concentrations tested. The current
study also characterized the hemocytes from hemolymph of larva of M. domestica by
their identification and quantification; also, we evaluated the effect of the strain S599 of
B. thuringiensis infection to the total hemocytes counts, and number and size of
hemocyte types, using optical microscopy. Collections were made at the times of 12, 24,
48 and 72 hrs. Five hemocyte types were found: prohemocytes, plasmatocytes,
granulocytes, oenocytoids and spherulocytes, in which plasmatocytes were found in
superior number. Prohemocytes were the smallest cells observed, and oenocytoids were
the biggest ones. The treatment of M. domestica larva with B. thuringiensis did not
change morpholigical characteristics of hemocytes, as well as it did not modify the
counts of hemocyte types. The total number of hemocytes in the hemolymph, however,
increased significantly 48 hours after the larval treatment. B. thuringiensis strains
selected in the current study are promising agents for biological control of M.
domestica.
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STEIN, A. E. K. Bacillus thuringiensis para controle de Musca domestica: seleção de estirpes e avaliação do perfil de hemócitos em larvas. 2017. 59 f. Dissertação (Mestrado em Biologia da Relação Parasito-Hospedeiro) - Universidade Federal de Goiás, Goiânia, 2017.