Sensitivity of immature stages of dengue causing mosquito, Aedes aegypti (L.) to gamma radiation

Aedes aegypti is a cosmopolitan urban mosquito that causes dengue every year in Bangladesh. The present study was carried out to observe the sensitivity level of immature stages of A. aegypti mosquito to gamma irradiation. Different developmental stages of A. aegypti were exposed to a series of irradiation doses in Co⁶⁰ gamma source to observe sensitivity regarding egg hatching, pupation, adult emergence, mortality and body size. Irradiation doses of 1-10 Gray were applied to eggs, 10-100 Gy to larvae and 10-250 Gy were applied to pupae. Egg hatching, pupae formation and adult emergence decreased with increasing dose (p = 0.000). Pupation decreased significantly (p = 0.000) with increasing radiation dose in 1st, 2nd, 3rd and 4th instar larvae. Regression analysis showed increase of percent mortality with increasing dose significantly in both 19-23 h old (early) and 42-46 h old (late) pupae (p = 0.000). A linear positive relationship was found between doses and mortality in both larvae and pupae. Irradiation of early and late pupae had no significant effect on adult emergence up to 40 Gy, however, while higher doses applied (100-250 Gy) emergence rate decreased significantly (p = 0.000). Lethal dose, LD50 and LD90 for 4th instar larvae were lower than pupae but higher than eggs. Even, LD50 and LD90 for early pupae were lower than late pupae. There was no significant effect of radiation on wing length compared to control (unirradiated) which were exposed to radiation at pupal stage (p = 0.153). Overall radiation had effect on egg hatching, pupation, adult emergence, mortality but had no effect on adult's body size of Aedes aegypti.