pax2a:venus expression in the adult zebrafish midbrain. (A) Scheme indicating a plane of coronal section of the adult zebrafish mid brain with optic tectum, hypothalamus and the pituitary corresponding to the cross section in “B” (orientation indicators A->P: anterior to posterior; D->V: Dorsal to Ventral). (B) Cross section of the midbrain immunostained against venus (green) and DAPI (blue). (C) in situ hybridization against pax2a in the midbrain similar to the coronal planes in “A,B” showing similar expression pattern as that of venus in the knock in reporter line. (D,F,H) Higher magnification of a midbrain indicated by white boxes in “B” showing neuronal nuclei expressing venus in regions, valvula cerebelli (red dotted line area) and dorsal tegmental nucleus (yellow dotted line area) “D,” neighboring (left side) to the lateral longitudinal fascicle “F” and the rostral tegmental nucleus “H.” (E,G,H) Higher magnification of a region from the midbrain tectum indicated by black boxes in “C” showing in situ expression pattern for pax2a showing highly similar pattern to their counter parts expressing pax2a:venus. Anatomical descriptions were based on (zebrafish brain atlas; Wullimann et al., 1996). Scale bars (B,C): 100 μm; (D,E,G,I): 20 μm; (F,H): 10 μm. (B: max intensity projection; D,F,H: single Z-Plane; C,E,G,I: DIC image).