Fig. 3. (A) Schematic illustration of a goldfish nephron based on morphological criteria previously outlined (Sakai, 1985). The goldfish nephron can be divided into the following regions: 1, renal corpuscle (Bowman's capsule and glomerulus); 2, proximal tubule; 3, distal tubule; and 4, collecting duct. (B) Cross-section of goldfish kidney immunostained for occludin (red) and Na⁺,K⁺-ATPase (green). Occludin and Na⁺,K⁺-ATPase show region-specific immunostaining along the nephron. Numbered labels indicate regions of the nephron as defined in A. No occludin or Na⁺,K⁺-ATPase immunostaining was found in the renal corpuscle. A control section can be seen in C (i.e. DAPI fluorescence only). All scale bars are 20 µm.