The genetics and ecology of male reproductive investments in the malaria mosquito Anopheles gambiae s.s
Ekechukwu, Nkuru Esther
Malaria continues to be a major global health problem due to high mortality and morbidity rate in endemic regions. An. gambiae s.s is the major vector in endemic African countries. About 198 million cases of malaria were recorded globally in 2013 and this have led to over 584 000 deaths. Different measures have been implemented in order to reduce and control the transmission rate. However, the drug resistant parasites and insecticide resistant mosquitoes have created problems towards achieving this goal. The use of the sterile insect technique and genetically modified mosquitoes as a control measure seems very promising but requires massive releases of males that are vigorous and competitive for the strategy to be realistic. Thus, there is need to understand the genetics and ecology of male mosquitoes with reference to their reproductive investments particularly for the laboratory reared An. gambiae due to inbreeding effects in colonized strains. Here we developed a qPCR technique based on TaqMan assay to quantify male sperm investment and used the assay to examine the effects of hydric stress on sperm investment by males and sperm maintenance in mated females. From two inbred strains of An. gambiae s.s, we generated heterotic supermales and tested for inbreeding and heterosis effects on sex peptide and sperm investments by males in large and individual male mating cages to determine male reproductive success. No evidence of heterosis was found in the large group mating cages except in sperm activity. However, in the individual male mating cages, the heterotic supermales achieved higher reproductive success than the inbred strains. They produced more eggs and fathered numerous larvae. Furthermore, inbreeding affects the size of the sex peptide deposited and survival in inbred males. Conclusively, heterosis could be the quickest method to produce vigorous and competitive laboratory reared males for vector control projects where male reproductive success is required.