Fig. 6. (A–E) UV opsin-ir in the retina and optic lobe (Cy3, red). Nuclei were stained with DAPI (blue). (A) UV opsin-ir of the most proximal part of the lamina (C-layer), adjacent to the first optic chiasm (arrow). (B) Adjacent section to A processed with the primary antibody omitted. Strong autofluorescence of the cuticle and trachea are indicated here and in C by arrowheads. (C) UV opsin-ir in the retina and the lamina. The width of the labeled neuropil increases towards the lateral edges of the lamina (bottom left). (D) Perikarya cluster at the ventral edge of the lamina (arrow). The maximum number of labeled cells we could detect in a single section was 15. (E) The column-like structure of the UV opsin-ir neuropil in the proximal part of the lamina. Two layers of nuclei border the labeled neuropil (blue). The structure of UV opsin-ir columns found in our study shows high similarity with the optical cartridges described at the same location in the honeybee by Sinakevitch et al. (2003) using reduced silver staining. Arrow indicates cell layer comprising glial nuclei or nuclei of the monopolar cells that communicate with the long photoreceptor cell fibers. (F) UV opsin mRNA detected by in situ hybridization using an antisense riboprobe. Hybridization signal was found in the perikarya of the two layers bordering the lamina columns (see also arrow in E) in between which the UV opsin-ir was detected and in perikarya at the distal rim of the medulla (arrowhead), adjacent to the first optic chiasm. (Inset) PER-like-ir (green) was found in the perikarya layer that is located adjacent to the distal rim of the medulla in the first optic chiasm and in the 3rd layer of the lamina (arrow). Nuclei are stained with DAPI (blue). Arrows in F and in the inset indicate similar location. D, dorsal; 1. Oc, first optic chiasm; La, lamina; Me, medulla; Re, retina; V, ventral. Scale bars, 50 µm (A,B,C,F); 20 µm (D,E).