Age-dependent mating dynamics, body size, and sex ratio in colonised Anopheles coluzzii.

Malaria is a serious life-threatening disease transmitted by Anopheles mosquitoes. Knowledge of physiological parameters associated with mosquito fitness is essential to understand mating dynamics, population structure, and the effectiveness of vector control interventions. This study investigated key biological parameters, including body size and insemination rate in relation to adult age, as well as sex ratio, in a laboratory-reared Anopheles coluzzii colony. A total of 1526 female mosquitoes were dissected, of which 1494 were included in the analysis; a significant non-linear relationship was found between age and insemination status (Quasibinomial GLM, F (1,48) = 265.3, P < 0.001). Insemination rates of 1-day-old females were low but not absent (mean ± SEM: 6.00% ± 2.5%); at three days, insemination rates were highly variable, ranging from 13.33% to 86.67%, suggesting inconsistent mating success, while the highest insemination rates were observed in older females. Morphometric analyses indicated that females presented significantly longer wings (mean ± SEM: 3.16 ± 0.01 mm) than males (mean ± SEM: 2.91 ± 0.01 mm), and that mosquitoes sampled at older ages had larger average wing lengths (F (1,57) = 5.60, P = 0.02). Moreover, a significant male-biased sex ratio was found, with males representing on average 52.0% (95% CI: 50.54-53.66%) of the emerged adults. Together, these findings provide detailed baseline data on age-dependent mating success, body size variation, and sex ratio structure in laboratory-reared An. coluzzii.