Figure 9. Mel1a and Mel1c immunocytochemistry of whole-mounted Xenopus laevis surface corneal epithelium obtained at 4-h intervals during a 24-h light–dark cycle. Frogs were housed under a 12 h:12 h light–dark cycle (6:00 AM: lights on; 6:00 PM: lights off). All tissues in this figure were obtained in the light. Mel1c labeling is represented in green (A, D, and G) and Mel1a labeling is represented in red (B, E, and H). The yellow labeling in the merged images (C, F, and I) indicates regions of co-localization of the red and green signal. A-C: Corneas obtained at 8:00 AM (2 h after lights on). Mel1c and Mel1a labeling is localized to the lateral plasma membrane of different yet overlapping subpopulations of cells. D-F: Corneas obtained at 12:00 N (mid-light). Mel1a and Mel1c immunolabeling is present on the lateral membranes of different populations of CE cells, with some minor regions of overlap. G-I: Corneas obtained at 4:00 PM (2 h before lights off). Most of the Mel1a and Mel1c immunolabeling is co-localized on the lateral membranes, with some cytoplasmic labeling that is not co-localized. Nuclei are stained with DAPI. The confocal images in all panels are comprised of three optical slices of 400 nm each in the z-series. The magnification bar (I) represents 20 µm.