A comparative study of malpighian tubules and rectum in the haematophagous dipterans: glossina and stomoxys

The medical and veterinary importance of Dipteran insects as well as the problems of the blood-sucking habit is outlined in the introductory chapter of the thesis. The excretory system of insects, which comprises the Malpighian tubules and rectum, and the variation in the organization of insect Malpighian tubules, is also outlined. In chapter II, a comparative analysis of the tubules of the tsetse, Glassina morsitans and stable fly Stomoxys calcitrans is given. There was ultra structural zonation in the Malpighian tubules of both insects; the tubules consisting of the distal, intermediate and proximal regions, which themselves had distinct cell types. A possible implication of the similarity in the ultra structural organization of the tubules of the two haematophagous dipteran insects is discussed in the thesis. Chapter III gives a description of the various cell types in the recta of G. M. morsitans and S. calcitrans. In chapter IV possible changes in the morsitans in relation to feeding is discussed. Observations made on G. M. morsitans tubules at various stages of a hunger cycle indicated that ultra structural changes in the unfolding of the epithelial cell basal plasma membrane and in the organization of some of the organelles were related to feeding. Preliminary morphometric analysis indicated that there was increase in the number of dense bodies after feeding in G. m. morsitans, suggesting greater synthetic and transport activity in the tubules. As discussed in chapter IV, functional zonation in the Malpighian tubules of G. m. morsitans was studied by auto radiography using titrated glucose. There was greater incorporation of the radiolabel in the distal and intermediate regions, which were secretory, than in proximal region which was absorptive. These observations indicated that structural zonation in G. m. morsitans tubules was closely related to their function.