Fig. 6. The completed pattern of R1-R6 connectivity was severely disrupted in adult otk mutants. Cryostat sections of wild-type (A,C) and otk³ eye-specific mosaic heads (B,D) were stained with MAb 24B10 to visualize all R-cell axons. In wild type (A), R7 and R8 axons projected into different layers within the medulla. Individual R7 and R8 axon terminals could be readily identified. In an otk³ mosaic head (B), the medulla appeared to be innervated by an increased number of R-cell axons. C and D are higher magnification views of the boxed region in A and B, respectively. Whole-mount wild-type (E) and otk³ mosaic brains (F) carrying an adult R1-R6 specific marker, Rh1-LacZ, were stained with anti-ß-galactosidase antibody. In wild type (E), LacZ staining was exclusively observed in the lamina, as all R1-R6 axons terminate within this layer. In an otk³ mosaic brain (F), a large number of R1-R6 axons (arrow) connected abnormally to the medulla. Scale bar: 20 µm in A,B,E,F; 5 µm in C,D.