SPERMIOGENESIS AND MEIOTIC DRIVE IN AEDES AEGYPTI

Abstract:
We recognise that insecticides must continue to play a major role in most control programmes against insect pests or vectors, particularly when there are emergencies which cannot wait for alternative means of control to be developed. We believe genetic methods should be given serious thought and investment, in any long term strategy. This opinion is strengthened against a background of (i) expanding insecticide resistance (ii) tightening regulation of insecticide use. (iii) multiple drug resistance in vector borne parasites and (iv) considerable progress made in genetic engineering and recombinant DNA research. In our recent work on spermiogenesis and meiotic drive in the mosquito, Aedes aegypti, we have established that some strains carry the distorter gene Don the Y chromosome which causes the production of more males than females, the proportion of females being below 12% in some cases. Any means of producing fewer blood engorging females must be good news. Electron microscopic studies on testes reveal evidence of massive degeneration of spermatozoa, reduction in their numbers within cysts and considerable degree of malformation, and early senescence in strains which respond to the effect of the meiotic drive by D. These features are evident in the testes of emergent males, which will not be ready to mate till 48 hours later (Christophers, 1960; Clements, 1992). Meiotic drive has been mentioned as one possible vehcle by which genes altered through recombinant DNA technology could be introduced into the populations (Eggleston, 1991). We would be the first to recognise the difficulties that lie ahead, in any attempt to exploit the potential of genetic control commercially The fact that most of the recommendations of the Rockefeller Foundation committee of experts (Hoy and McKelvey,1979) still remain unfulfilled a decade and a half after they were made, in spite of a considerable increase in knowledge of gene technology puts aspirations for genetic control in perspective. At the same time we believe that any progress in this direction is better than none at all.