Squid olfactory epithelium. A: Arginine. The image is marked to indicate the main features of the OE. The AOI mask is overlaid and color-coded (see legend in Fig. 3) by class: 1, blue; 3, red; 4, green; 5, cyan; 6, fuchsia; 8, peach; 10, cream; 11, pink; 12, maroon (Classes 2, 7 and 9 see Fig. S5). B: Aspartate. C: Glutamate. D: Glycine. E: GSH. F: Taurine. G-H: RGB images of the squid OE. I: Higher magnification image of area within white dashed line in G. Numbers, arrows and arrowheads indicate the Class number. CP, cilia pocket; CT, connective tissue; T2, type 2 ORN; T3, type 3 ORN; T4, type 4 ORN; T5, type 5 ORN; basal lamina; dashed line in A. Scale bars = 10 μm.