Role of hemocytes of Lymantria dispar larvae during an infection with entomopathogenous microsporidia
Abstract
Microsporidia are unicellular, obligate intracellular parasites that infect hosts of all animal groups; in insects they have potential as biological control agents. The typical life cycle of a microsporidium in the genera Nosema or Vairimorpha in a host insect begins in the gut tissue, from where the infections spreads to the target tissues, such as fat body or silk gland where environmentally resistant spores are produced. In a previous study, we showed that L. dispar larvae react to microsporidian infections with increased melanization capacity of the hemolymph. In some cases, also hemocytic encapsulations of infected tissues could be observed. Frequently hemocytes (both, free and in aggregations) contain microsporidian cells. However, it remains unknown, to what extent this encapsulation can confine the infection or if microsporidia are able to utilize the host hemocytes. We will test whether hemocytes allow successful development of microsporidia and whether they can function as a means to spread the infection within the host. Therefore, we will infect L. dispar larvae orally with microsporidia and after various periods of incubation recover hemocytes from these insects. The hemocytes will be examined under the light microscope for the presence and developmental stage of microsporidia. Infected hemocytes will be purified and injected into uninfected L. dispar larvae. At different points in time, larvae will be dissected and inspected for microsporidian infections under the light microscope. Different timing of harvesting, injection, and dissection will prove whether hemocytes can successfully be utilized by microsporidia and whether a particular developmental stage is able to use host hemocytes to spread the infection within the host body.