Challenging popular belief, mosquito larvae breathe underwater

Abstract

It is taken for granted that immature mosquito only breathe atmospheric air through their siphons. However, there is no quantitative study that demonstrated it. We analysed the survival of the last instar larvae of Aedes aegypti fully submerged at different temperatures, and measured oxygen consumption from air and dissolved in water, of larvae and pupae of this species under different conditions. Results revealed that under water, larvae survived much longer than expected, reaching 50% mortality only after 58, 10, and 5 days at 15{degrees}, 25{degrees} and 35{degrees}C, respectively. Interestingly, whereas we registered moults to pupae in larvae with access to air, individuals kept submerged never moulted. When remaining at the water surface, larvae obtained 12.72% of O2 from the water, while pupae only 5.32%. When completely submerged, larvae consumed less oxygen than in contact with the surface, but enough for surviving, while pupae did not. At both media, temperature affected larvae respiration rate, with relatively close Q10 values. In the related species, Ae. albopictus, a similar pattern of O2 consumption were observed. Larvae got 12.14% of their oxygen from the water. Interestingly, no significant differences in total O2 consumption were found between water O2 consumption, when Ae. albopictus larvae were submerged, or when they also have access to air (dual O2 consumption). Our findings not only challenge the classical idea that mosquito larvae only breathe atmospheric O2, but also force us to reconsider the potential effectiveness of control methods based on asphyxiating larvae by detaching from water surface. Summary statementWe present the first quantitative analysis of mosquito larvae respiration in air and water, unravelling the unknown capacity of larvae of the most cosmopolitan disease vector of breathing underwater.