Imunidade celular em operárias de formigas-cortadeiras (Hymenoptera: Formicidae), coletadas em áreas externas ao ninho

Abstract

Leaf-cutting ants are social insects of great agronomic importance due to the defoliation they cause in various crops. The innate immune system of insects, especially in eusocial ones, is crucial for defense against pathogens and maintaining individual and colony health. The cellular immune response is carried out by cells present in the hemolymph, called hemocytes, which perform functions such as encapsulation, nodulation, phagocytosis, and melanization. Insects produce various types of hemocytes traditionally identified using morphological, histochemical, and functional characteristics. This study was divided into two chapters. The first chapter investigated the relationship between the size of the head capsule of two groups of workers - foragers and larger workers outside the nest, referred to as "soldiers" - and the quantity of freely circulating hemocytes in the hemolymph of leaf-cutting ants Atta laevigata and Atta sexdens. Hemocyte quantity was quantified in a Neubauer chamber, along with head capsule width. In the second chapter, hemocyte types in the hemolymph of Acromyrmex balzani, A. sexdens, and A. laevigata were characterized and determined. Hemocyte counting and identification were conducted at the Laboratory of Insect-Microorganism Symbioses (LASIM), Federal University of Tocantins, Gurupi Campus. To quantify the numbers of each hemocyte type, ImageJ software was used for slide analysis. After hemolymph extraction from ten workers of each species using capillarity, three slides were prepared for each species. These slides were stained using the May Grunwald-Giemsa staining method for hemocyte visualization. The area of the slide was quantified using the ImageJ program, allowing determination of the quantity of each type of hemocyte present. Additionally, correlation analyses for variables related to cell types present in the hemolymph were performed using the R Core Team program. This step allowed investigation of possible relationships between the abundance of different hemocyte types and other variables studied, such as morphological characteristics of ants or environmental conditions of the nests.