Overlapping experession of Tt - c - opsin and Tt - Pax6 in the apical lobe. (A) Dorsal and (B) lateral views of Tt-c-opsin expression in the apical lobe of the middle larva stage. Strong expression is observed in two lateral lines of punctate staining, matching the position of the larval eyes (black arrows). (C, D) Tt-Pax6 is expressed in a broader domain at the same stage. The anterior edge of the Tt-Pax6 expression domain overlaps with that of Tt-c-opsin (white arrows). (E-H) Two-color fluorescent in situ with Tt-Pax6 and Tt-Otx probes. All images are of the same embryo. (E) Single confocal section of Tt-Pax6 expression (white arrows). Fluorescence at the edge of the apical lobe (white arrowheads) is due to endogenous autofluorescence of the vesicular bodies. Fluorescence between the mantle and pedicel lobes (blue arrowheads) is due to probe trapping. (F) Single confocal section of Tt-c-opsin expression (white arrows). Fluorescence between the mantle and pedicel lobes (blue arrowheads) is due to probe trapping. (G) Single confocal section showing overlapping Tt-Pax6 (green) and Tt-c-opsin (purple) expression (white arrows). (H) Single confocal section of Tt-c-opsin expression (purple; white arrows) overlayed with a DIC image to show the morphological position of expression domains.