Get access

Mating, ovariole number and sperm production of the dengue vector mosquito Aedes aegypti (L.) in Australia: broad thermal optima provide the capacity for survival in a changing climate


Craig R. Williams, Sansom Institute for Health Research, GPO Box 2471, University of South Australia, Adelaide, South Australia 5001, Australia. Tel.: +61 883021906; e-mail:


Little is known about mating, ovariole number and sperm production of Aedes aegypti (L.) in Australia, especially in relation to climate. To determine the extent of interpopulation variation and thermal dependence of reproductive traits in A. aegypti, laboratory studies are conducted using colonies originating from up to four locations in Queensland, Australia. Observations of insemination reveal that these behaviours are temperature-dependent, although humidity levels appear to have little effect, with only small increases in insemination at higher humidities. No noteworthy variations in thermal optima (temperature ranges within which maximal performance occurs) for such behaviours are observed between colonies, with all showing high levels of insemination between 25 and 35 °C. Both male and female maximum fecundity for A. aegypti are also found to be temperature-dependent. Sperm counts, not hitherto obtained for Australian A. aegypti, range from approximately 3000–5000 per male, with counts increasing with increased rearing and holding temperature, despite a decreasing body size. Conversely, ovary size decreases with temperature and body size, from approximately 100 ovarioles per female at 17 °C, to 85 at 35 °C. The lack of variation in reproductive capacity between colonies of different geographical origin indicates that any locally-acting selective pressures are not driving divergence in key reproductive traits such as insemination ability and fecundity. This may be because the source populations used are not from sufficiently diverse climates. Nonetheless, the broad thermal optima for reproductive traits in A. aegypti are suggestive of limitations on these traits not being responsible for limiting distribution and population growth in the event of projected mean temperature rises.