Autogeny in diverse populations of Aedes aegypti from East Africa

Autogeny in Aedes aegypti was found in many diverse populations throughout the range of East Africa. Degree of autogeny is proposed to be measured either by a relative method using an autogeny index (AIX), or by direct count of eggs in dissected ovaries and expressed in percentage. Degree of autogeny varied from population to population but it was always higher in the dark feral Ae. aegypti formosus than in the domestic Ae. aegypti aegypti form. The highest degree of autogeny occurred in the dark form frm Uganda, where in some populations it was as high as 34%. Some autogenous females have a tendency to retain fully developed eggs in their ovaries up to 4 weeks for later oviposition. At the beginning of oogenesis, the autogenous females deposit yolk granuli in many follicles. As soon as the follicles reach the resting stage, translocation of yolk from many to few follicles takes place. The number of eggs developed autogenously depends on the level of nutritional reserves carried by the females from the larval stage. Autogeny could possible serve as one of the preservation mechanisms of haematophagous species when hosts are not available. The vectorial capacity of autogenous populations of Ae. aegypti for transmission of pathogens is substantially lower than anautogenous ones because of their nonhaematophagous feeding behavior at the first gonotrophic cycle and shorter survival of females.