(A) Representative histology of pancreatic and gut tissue immunostained with antibodies against insulin (green) and BrdU (red). As expected, criptae of the gut, at the bottom, are strongly positive for BrdU. (B, C, E) Pancreatic islets from 9 months (B and E) and 5 months old fish (C) immunostained for insulin (green) and BrdU (red) and counterstained with DAPI (blue). White arrowheads indicate insulin and BrdU copositive cells. (D) Proliferation of beta cells, although at a low rate, was also confirmed by PCNA immunostaining as indicated by the arrowhead. (F) Histology of proliferating alpha/delta cells within an islet stained with antibodies against glucagon and somatostatin (cytoplasmic red). A white arrowhead indicates a glucagon/somatostatin producing cell copositive for BrdU (light nuclear red). (G) Representative pancreatic section showing a proliferating hormone negative cells (white arrowhead). Scale bar: 100 μm.