Fig. 4. Comparison of the rectal structure of the freshwater culicine Ae. aegypti (A), the saline-tolerant culicine Oc. taeniorhynchus (B), and the freshwater anopheline, An. gambiae (C) using confocal microscopy of whole mount immunohistochemical preparations. Similar data have previously been reported (Patrick and Gill, 2003; Smith et al., 2007; Okech et al., 2008). Protein localizations are shown for visual distinction of rectal segments in each species. Freshwater culicine larvae possess a structurally uniform rectum as shown by Na⁺/K⁺-ATPase (red) localization (A) whereas saline-tolerant culicine larvae possess a rectum structurally divided into distinct anterior (AR) and posterior (PR) regions as shown by the localization of Na⁺/K⁺-ATPase (red) to the AR and V-ATPase (green) to the PR (B). By contrast, both freshwater and saline-tolerant anopheline larvae possess a unique type of segmented rectum, which differs from culicines and consists of a patch of cells on the dorsal anterior region of the rectum (DAR cells), which are distinguishable from the rest of the rectum (non-DAR cells) as shown by the localization of Na⁺/K⁺-ATPase (red) to the non-DAR cells and CA9 (blue) to the DAR cells (C). AR, anterior rectum; DAR, dorsal anterior rectum; PR, posterior rectum. Scale bars: A,C, 150 µm; and B, 186 µm.