Morphometric parameters of the midgut cells of Aedes aegypti L. (Insecta, Diptera) under various conditions

Previous morphometric or biochemical investigations have yielded different data on the distribution of free and membrane-bound ribosomes in midgut cells of Aedes aegypti. In the present paper ribosomal distribution has been morphometrically analysed to determine whether different mosquito strains, different food and different narcosis used in these previous studies, and/or methodological errors, could account for the different results. Most of the cellular parameters in the stomach epithelium of female A. aegypti, strain Rockefeller, and their changes during blood digestion, are comparable to those measured for another Aedes strain (Segemaganga, Hecker and Rudin, 1979), and ae generally similar to those of Anopheles stephensi (Hecker 1978). Proteolytic activity against casein is similar for both Aedes strains with a maximum activity being registered around 30 h after a blood meal. During digestion of human serum there is no increase in the ratio of membrane-bound to free ribosomes, and no significant increase in the surface area of the rough endoplasmic reticulum or of the number of bound or free ribosomes. Proteolytic activity is distinctly lower than during blood digestion. Immobilization of mosquitoes prior to dissection by either narcosis or by shaking in a test tube has no significant influence on cellular parameters in females fed on sugar solution and investigated 3 days after emergence. It is concluded that the differences in ribosomal parameters previously obtained by morphometrical (Hecker and Rudin 1979) and biochemical (Gander et al. 1980) methods, can only partly be explained by the selection of different food for the mosquitoes, and must also have been caused by methodological inadequacies.