Salinity Responsive Aquaporins in the Larval Mosquito Aedes Aegypti

The anal papillae (AP) of the mosquito larva, Aedes aegypti are important sites for ionoregulation because they actively take up ions from a dilute external environment to help maintain appropriate ion levels in the hemolymph. An apparent paradox is that these structures are also permeable to water and because of the syncytial nature of the epithelium, aquaporins (AQPs) are likely to be involved. A previous study has revealed expression of AQP homologs in the anal papillae of freshwater reared larvae. In the present study, transcript expression levels of six AQP homologs in the AP were examined in larvae reared in ion poor water and 7.5 g L-1 Instant Ocean® salts (~ 30% seawater). The mRNA expression of four of these AQP homologs (AaAQP2, AaAQP3a, AaAQP3b, AaAQP4) was salinity responsive suggesting the importance of these homologs in salinity acclimation. In addition, western blot analysis of AaAQP3a and AaAQP3b confirmed the salinity responsive nature of these two proteins. Immunohistochemistry also confirmed the presence of AaAQP3a and AaAQP3b in both the apical and basal membranes of the AP.