Patogenicidade de Metarhizium Anisopliae em combinação com sulfato de zinco em operárias de Atta Sexdens

Abstract

In order to evaluate the pathogenicity of M. anisopliae in combination with ZnSO4 in A. sexdens workers, three experiments were carried out in the Laboratory of the Insect-microorganism symbiosis at the Federal University of Tocantins. The experiments were divided into two chapters. The first one aimed to evaluate the effects of ZnSO4 as an immunosuppressive substance in A. sexdens workers. The experimental design consisted of seven replicates (0, 0.15, 0.25, 0.50, 1.50, 2.50 and 5.00 g/L) of ZnSO4, with eight replicates (containing 1 worker per replicate) and two evaluation periods (24 and 48 hours). For each dose, the repetition was immersed for 20 seconds, later each worker was individualized in glass test tubes with moistened cotton. After 24 and 48 hours, 1μL of hemolymph was removed from the occipital region of the head of each worker and the total hemocytes was counted using a Neubauer chamber. The doses of ZnSO4 were efficient in reducing the number of hemocytes of the workers in both periods. The two schedules evaluated presented a high performance in the common dose: 0.15 g/L of ZnSO4. The period of 48 hours presented greater interference in the immunity of the workers. The second chapter aimed to verify the increase in the mortality of A. sexdens workers associating ZnSO4 with the fungus M. anisopliae. The experiment was composed of three treatments: 105, 106 and 107 conidia / mL of the fungus M. anisopliae, with 3 replicates each, being divided into 10 groups with 10 workers each and one control consisted of the application of autoclaved distilled water. Each worker received 1 μl of suspension in the thorax in each corresponding treatment and placed in BOD. In the evaluation, the dead workers were collected every day and disinfected, placed in autoclaved Eppendorf tubes and placed in BOD to confirm if the death was caused by M. anisopliae. The dose of 106 conidia / mL presented intermediate mortality and was chosen for the second stage of the experiment. ZnSO4 allowed opportunistic fungi to become pathogenic. The association between ZnSO4 and M. anisopliae was efficient to promote the activity of M. anisopliae by increasing the infection rate and mortality from 30% (treatment with fungus suspension only) to 60%.