The structure of the female sand fly (Phlebotomus papatasi) alimentary canal

In the sand fly vector, Leishmania parasites are confined to the alimentary canal. During much of their development, promastigotes are attached to the wall of the gut via their flagella. In this context, the surface of the different regions of the sand fly alimentary tract lumen warrants scientific attention. In this paper, the various regions are described, for the first time using scanning electron microscopy. The cibarium and the pharynx, which function as pumping organs, are lined with cuticle. Parts of the cibarium and the pharynx bear different types of cuticular spines and appendages. The midgut is lined with microvillar epithelium, which secretes the peritrophic matrix following a blood meal. The wider proximal part of the hindgut (= pylorus) is lined with transverse cuticular ridges with tentacle-like appendages. Leishmania major promastigotes were found to anchor themselves in the midgut and the stomodaeal valve via their flagella. The possible roles of the different internal structures and their importance for the development of Leishmania parasites are discussed.