EFFECTS OF PLASMODIUM-YOELII NIGERIENSIS INFECTION ON ANOPHELES-STEPHENSI EGG DEVELOPMENT AND RESORPTION

It has been shown previously that infection with Plasmodium yoelii nig eriensis reduces the number of eggs produced by female Anopheles steph ensi. Here we examine the mechanism underlying fecundity reduction. Ov aries from infected and uninfected (control) female mosquitoes were ex amined 12, 24 or 36h after blood-feeding during the first gonotrophic cycle (replicated) or the second gonotrophic cycle (unreplicated). Fol licular development was assessed according to Christophers' stages and the proportions of developing and resorbing follicles per ovary were determined. Resorption of some follicles commenced within 12 h of bloo d-feeding, affecting significantly more follicles in the infected fema les: 1.1% v. 3.2%. The difference was greatest 36h after blood-feeding : 25% reduction (10 v. 35%) in the first cycle; 16% reduction (9 v. 25 %) in the second gonotrophic cycle. The mean speed of oogenesis was al so found to be significantly retarded in infected mosquitoes. During t he second gonotrophic cycle, for example, only 92-94% of follicles rea ched stage III by 24h and stage IV by 36h in infected females, whereas all the developing follicles of uninfected females reached these stag es more or less synchronously in the time specified.