We use RNA-Seq to investigate gene expression differences in response to saltwater exposure by the larval stages of the obligate freshwater mosquito Anopheles coluzzii (formerly An. gambiae "M" form), and the euryhaline An. merus. Overall design: After rearing in freshwater, both young and old larval instars of each species were briefly (6 h) exposed to either saltwater (SW) or freshwater (FW) conditions to test the impact of salinity on mRNA levels.