The effect of dieldrin exposure on Anopheles gambiae (Diptera: Culicidae): fitness, fecundity and fertility.

Abstract

The effect of dieldrin exposure on fecundity, fertility and longevity was investigated in two populations of the African malaria vector Anopheles gambiae s.s: A wild representative strain and a laboratory strain were used. Experimental procedures were designed and optimised to obtain the maximum amount of data for individual females. In some instances, novel experiments had to be designed to answer specific research questions as no similar studies were available in the literature. A compilation of reference photographs depicting the different stages of oocyte growth in An. gambiae females was produced to assist in the identification of growth phases. Fecundity was shown to be reduced in dieldrin exposed females with close correlation to egg retention. Oocyte developmental rate was reduced in both populations of mosquitoes after exposure to dieldrin. Longevity was observed to decrease in the wild strain and remained unchanged in the laboratory strain when compared to the unexposed controls. Fertility was generally decreased, however dieldrin exposure appeared to have no negative affect on mating or spermatozoan viability before or after mating in male testes or female spermathecae respectively. In summary this study showed that exposure to dieldrin had subtle effects on the biology of these mosquitoes, but would probably not have a detrimental effect on a population as a whole.