Stopping male mosquitoes from sealing their sperm inside females with a 'mating plug' could prevent mosquitoes from reproducing, and offer a potential new way to combat malaria, say scientists publishing new results in PLoS Biology on 22 December.
The new study focuses on the species of mosquito primarily responsible for the transmission of malaria in Africa, known as Anopheles gambiae. These mosquitoes mate only once in their lifetime, which means that disrupting the reproductive process offers a good way of dramatically reducing populations of them in Africa.
When they mate, the male transfers sperm to the female and then afterwards transfers a coagulated mass of proteins and seminal fluids known as a mating plug. This plug is not found in any other species of mosquito and until now, very little has been known about what it is for and the role it plays in An. gambiae reproduction.
The authors of today's study, led by Imperial College London, have shown for the first time that the mating plug is essential for ensuring that sperm is correctly retained in the female's sperm storage organ, from where she can fertilise eggs over the course of her lifetime. Without the mating plug, sperm is not stored correctly, and fertilisation cannot occur.
In Imperial's mosquito labs, the scientists showed it was possible to prevent the formation of the plug in males, and that this stopped them successfully reproducing with females.
Lead author Dr Flaminia Catteruccia, from Imperial's Department of Life Sciences, explains the significance of their discovery:
"We have shown that the male mating plug is not a simple barrier to insemination from rival males, as has been previously suggested. Instead, we discovered that the plug plays an important role in allowing the female to successfully store sperm in the correct way inside her, and as such is vital for successful reproduction.
"Removing or interfering with the mating plug renders copulation ineffective. This discovery could be used to develop new ways of controlling populations of An. gambiae mosquitoes, to limit the spread of malaria."