The objectives of this study were to investigate basic descriptions of reproductive biology and mating behaviors of the principle mosquito vector of dengue fever and dengue hemorrhagic fever, Aedes aegypti. Physical traits and environmental conditions that influence Ae. aegypti mating success in the laboratory and a dengue endemic area of Thailand were determined.
This is the first study to report on the effect of male mosquito age and body size on sperm number in three laboratory strains (Thai laboratory, Mexico, and Rockefeller) and one Thai wild strain of Ae. aegypti. Sperm number in Ae. aegypti males increased significantly up to 10 days after emergence and leveled off until 20 days old. After 20 days of age, the number of sperm decreased. Male body size was a major positive predictor of total sperm number with significantly greater numbers in large males compared to small males within the same age group. Variation among laboratory and field strains was observed, with Thai wild strain males producing greater numbers of sperm than all laboratory strains.
The effect of male age, female body size, density, and ambient conditions as influential factors in mating success of the dengue vector, Ae. aegypti were determined. Male age had an effect on insemination rate under both laboratory and field conditions with older males had higher insemination rate than younger males. Female body size is deemed to be a major physical factor affecting female mating success. These results demonstrated that larger virgin females were inseminated by all age group males more frequently than smaller ones did. Insemination in small cages occurred more frequently than in the large ones when number of mating pairs was kept the same. In conclusion, these results suggest that older (10 day old), larger males and larger females of the dengue vector, Ae. aegypti, under the field conditions have the greatest mating success.
Comparison of total number of eggs produced by females that mated once with a male within the same body size in different age groups (1, 5 and 10 day old) were significantly different. There was no difference between the percentages of viable eggs produced by females that mated with 1, 5 and 10 day old males. Thai wild strain Ae. aegypti females that mated once with 1-day-old males produced significant greater number of eggs than females mated with 5 and 10 day old. Female Ae. aegypti survivorship was not correlated with mated male age. In addition to male age, the difference between the survivorship of mated and unmated females was not detected. Interestingly, the overall fitness (expected number of daughters and net replacement rate) for females mated with younger males was greater than for those who mated with older males.
Further investigations of wild population in the dengue-field conditions are clearly required in order to reflect the natural mating behavior of Ae. aegypti and have robust implications for dengue vector control in the future. The knowledge of mosquito mating behavior and optimal physical traits are relevant to vector control, especially to improve efficiency of genetically modified or sterile male Ae. aegypti control programs.
