Comparison of male reproductive success in malaria-refractory and susceptible strains of Anopheles gambiae
Date
2008-06-05
Authors
Voordouw, Maarten J
Koella, Jacob C
Hurd, Hilary
Journal Title
Journal ISSN
Volume Title
Publisher
BioMed Central
Abstract
Background: In female mosquitoes that transmit malaria, the benefits of being refractory to the
Plasmodium parasite are balanced by the immunity costs in the absence of infection. Male
mosquitoes, however, gain no advantage from being refractory to blood-transmitted parasites, so
that any costs associated with an enhanced immune system in the males limit the evolution of
female refractoriness and has practical implications for the release of transgenic males.
Methods: Aspects of the male cost of carrying Plasmodium-refractory genes were estimated by
comparing the males' immune response and reproductive success among strains of Anopheles
gambiae that had been selected for refractoriness or extreme susceptibility to the rodent malaria
parasite, Plasmodium yoelii nigeriensis. The refractory males had a stronger melanization response
than males from the susceptible line. Four traits were used as correlates of a male's reproductive
success: the proportion of females that were inseminated by a fixed number of males in a cage
within a fixed time frame, the proportion of females with motile sperm in their spermathecae, the
proportion of ovipositing females, and the mean number of eggs per batch.
Results: Although there were significant differences among groups of males in sperm motility and
oviposition success, these differences in male reproductive success were not associated with the
refractory or susceptible male genotypes. Contrary to expectation, females mated to early
emerging refractory males laid significantly more eggs per batch than females mated to later
emerging susceptible males. Sperm motility and oviposition success were strongly correlated
suggesting that variation in sperm motility influences female oviposition and ultimately male
reproductive success.
Conclusion: An increased melanization response in male A. gambiae does not diminish male
reproductive success under the experimental protocol used in this study. That refractory males
induced ovipositing females to lay more eggs than susceptible males is an interesting result for any
strategy considering the release of transgenic males. That sperm motility influences female
oviposition is also important for the release of transgenic males.
Description
BioMed Central
Keywords
Citation
Voordouw et al.: Comparison of male reproductive success in malaria-refractory and susceptible strains of Anopheles gambiae. Malaria Journal 2008, 7:103.