Aedes albopictus, Aedes fluviatilis, Culex quinquefasciatus, Anopheles aquasalis and Anopheles

The fat body is the main storage and intermediary metabolism organ of insects and is responsible for the synthesis and supply of haemolymph substances. It consists of a mass of cells located underneath the epidermis and, in some insects, the fat body also surrounds the digestive and reproductive organs (reviewed by Haunerland & Shirk 1995 and Roma et al. 2010). Fat body cells, known as trophocytes, are clustered together by a thin basal lamina that expands into the haemocoel and forms amorphous lobes or ribbons that increase the organ surface area, which in turn enhance the exchange of substances between the organ and the haemolymph (Martins & Pimenta 2008, Arrese & Soulages 2010). Trophocytes are mesodermic with a cytoplasm rich in lipids, proteins and glycogen that provide energy and nutrients used mainly for insect locomotion and reproduction (Haunerland & Shirk 1995, Arrese & Soulages 2010). Ectodermic cells, such as oenocytes, are also present in the mosquito fat body (Martins et al. 2011c). Oenocytes can be associated with either epidermal cells or trophocytes whose functions are linked with the synthesis of hydrocarbons and homeostasis (Gutierrez et al. 2007, Martins et al. 2011b). Among blood-sucking insects, mosquitoes are considered the most important disease vectors, with several species involved in the transmission of pathogens such as helminths, protozoans and arboviruses to humans and animals (Eldridge 2004). Despite their importance, many aspects of the physiology of mosquitoes, such as the morphophysiology of the fat body, have been poorly researched. Clearly, the vast number of species encompassing the various mosquito vectors contributes to the difficulty of bridging such knowledge gaps. The fat body of the yellow fever mosquito Aedes aegypti has been extensively studied with regards to the storage of proteins and lipids used during morphogenesis (Marinotti et al. 2006), the role of lipophorins in lipid transport (Roy et al. 2007), the synthesis of vitellogenin for egg maturation (Roy & Raikhel 2011) and the detoxification of ammonia from blood meal proteins (Scaraffia et al. 2010). Predominantly, Ae. aegypti has been the focus of recent research on the mosquito’s innate immunity (Bian et al. 2005, Feitosa et al. 2006, Antonova et al. 2009). Despite this wealth of information on the basic functions of the fat body, little is known regarding the structural organisation of the fat body in mosquitoes other than Ae. aegypti. Our recent data on morphological aspects of the Ae. aegypti fat body revealed the differential staining properties of cells and the fat body’s capacity to change at the cellular and subcellular levels according to adult female nutritional status (Martins et al. 2011c). We now extended our investigation to include a comparative structural analysis of the fat body of five adult mosquito species including Aedes albopictus, Aedes fluviatilis, Culex quinquefasciatus, Anopheles aquasalis and Anopheles darlingi. Our approach utilised light microscopy (coupled with histochemistry) along with high magnification scanning and transmission electron microscopy (SEM and TEM) to assess differences in the fat body morphology of these important mosquitoes. Our analyses revealed, for the first time, general and detailed overviews of these mosquito fat bodies. The results obtained Financial support: CNPq, FAPEMIG, FIOCRUZ, NIH (AI074691 and AI083831 to JMR-O) + Corresponding author: [email protected] Received 19 March 2011 Accepted 17 June 2011 A comparative study of fat body morphology in five mosquito species