CLARK, T.M.; FLIS, B.J.; Indiana Univ. South Bend; Indiana Univ. South Bend: Identical pH Tolerances of Saline Water and Freshwater Aedes Mosquito Larvae

The pH tolerances of larvae of the freshwater mosquito Aedes aegypti and the salt marsh mosquito Aedes taeniorhynchus are identical. Each species can develop to the pupal stage in waters ranging from pH 4 to pH 11. Hemolymph pH is well regulated throughout the entire pH range. Duration of the larval stage, pupal mass, and larval growth rate are remarkably robust to pH but are influenced strongly by species and sex. Further studies in A. aegypti show that the ionic composition of the water (3.5 g/L sea salt, 3.5 g/L NaCl, or nominally NaCl free) has no effect on the range of pH that is tolerated but influences the relationship between growth rate and pH. In particular, sea salt enhances performance at low pH. Acclimatization to pH 4 enhances survival in pH 3, and acclimatization to pH 11 enhances survival in pH 12. Such acclimatization extends rather than shifts the range of tolerable pH, as larvae acclimatized to one extreme have no reduction in survival at the other extreme. Transfer of acclimatized larvae from pH 4 to pH 11 has no discernable effect on growth or development whereas transfer from pH 11 to pH 4 slows growth of females only. Larvae reared in pH 11 maintain the pH of the anterior midgut > 9.8 when transferred to pH 4.