Histological changes in the larvae of the domestic mosquito Culex pipiens treated with the entomopathogenic fungus Beauveria bassiana

Abstract

The Culicidae are biting insects that are most harmful to people. They are almost all blood-suckers, and are responsible for the spread of many important diseases such as malaria, yellow fever and elephantiasis. Entomopathogenic microorganisms occupy an important place among the alternative methods of fighting against pests insect. The fungus, Beauveria bassiana is an entomopathogenic agent naturally present in the ecosystems and offers a very interesting potential for controlling populations of mosquitoes. Our study aims at showing the 4th stage larvae histological changes of the domestic mosquito Culex pipiens, treated with the entomopathogenic fungus B. bassiana in suspension which corresponds to a dose of 107 spore/mL. In fact, after developing the individuals in the fungal solution, histological study was carried out on the following parts; cuticle, intestine, adipose tissue and hemolymph. The histological studies showed many alterations and malformation in the treated 4th instar larvae body and tissues. The infection affected the different parts of the body, especially the cuticle, the adipose cells, and midgut, in addition to the development and the colonization of B. bassiana inside tissues. The application of B. bassiana on the cuticle of the larvae was dependent on an apparent disturbance in the structure of the cuticle or the degeneration of its different parts. The fungus infection does not stop at the level of the body walls, so it even goes to adipose tissue, epidermal cells and intestine. Based on these results, B. bassiana could be suggested as suitable biocontrol agent against C. pipiens.   Key words: Beauveria bassiana, Culex pipiens, cuticle, histological study, midgut, adipose tissue.