EFFECT OF PLASMODIUM-YOELII NIGERIENSIS (HAEMOSPORIDIA, PLASMODIIDAE)ON ANOPHELES-STEPHENSI (DIPTERA, CULICIDAE) VITELLOGENESIS

Our previous studies demonstrated a significant reduction in the egg p roduction and survival of Anopeles stephensi Listen infected with Plas modium yoelii nigeriensis Killick-Kendrick. We investigated the physio logical mechanism underlying the malaria-induced curtailment of reprod uctive fitness. Polyclonal antibodies were raised against An. stephens i vitellin (Vn) and used in an enzyme immunoassay to quantify ovarian Vn and hemolymph vitellogenin (Vg) at 8, 12, 16, 20, 24, and 48 h post blood feeding in infected and noninfected mosquitoes. Initially, the c oncentration of Vg in the hemolymph and the accumulation of Vn in the ovaries of infected females were identical to females fed on noninfect ed mice, indicating that the synthesis of yolk protein by the fat bodi es was initiated normally. However, there was a significant reduction in ovarian Vn at 24 and 48 h postblood feeding and a significant accum ulation of Vg at 20 and 24 h postblood feeding in the hemolymph of inf ected mosquitoes. This increase in concentration of Vg in the hemolymp h just before Vn reduction in the ovaries of infected mosquitoes indic ated that synthesis at the fat body level may not be affected, but tha t sequestration of Vg by ovarian follicles of malaria-infected mosquit oes may be affected before resorbing follicles lose protein.