Representative sagittal sections of intestine, liver and pancreas of Atlantic salmon juveniles at various time points (days post hatch [dph]).

<p><b>(A)</b> General overview of the intestine at 27 dph; <b>(B-E)</b> Development of the proximal intestine; absence of pyloric caeca at 7 dph (B), appearance of pyloric caeca buds at 27 dph (C), and more developed pyloric caeca at 46 and 54 dph (D and E); <b>(F-I)</b> Development of the distal intestine; presence of incipient mucosal folds without goblet cells at 7 dph (F), appearance of mucosal folds scattered with goblet cells (arrows) within epithelium at 27, 46 and 54 dph (G-I), and presence of low level of supranuclear vacuoles at 54 dph (I); <b>(J-K)</b> Development of the mid intestine; simple epithelium without goblet cells at 7 dph (J), and following appearance of mucosal folds scattered with goblet cells at 46 dph (K); <b>(L-M)</b> Development of the rectum (re); epithelium consisting of cuboidal cells devoid of mucus cells at 7 (L) and 46 (M) dph; <b>(N-P)</b> Development of the liver (li) consisting of polygonal hepatocytes with a prominent basophilic nucleus and eosinophilic cytoplasm irregularly arranged along the sinusoids around a central vein; increasing accumulation of glycogen-containing vacuoles (arrows) in hepatocytes from 7 (N) to 46 (O) dph; low level of glycogen deposit in liver following start-feeding at 54 dph (P); <b>(Q)</b> Fully differentiated pancreatic tissue composed of exocrine cells with zymogen granules (arrows), endocrine cells grouped in Langerhans islets, and pancreatic ducts at 7 dph. Abbreviations: bd, bile duct; ct, connective tissue; cv, central vein; di, distal intestine; e, epithelium; en, endocrine pancreas (Langerhans islet); ex, exocrine pancreas; gb, gallbladder; gc, goblet cell; li, liver; lp, lamina propria containing connective tissue; mf, mucosal folds; mi, mid intestine; pa, pancreas; pc, pyloric caeca with simple, columnar epithelium and goblet cells; pd, pancreatic duct; pi, proximal intestine; pyb, pyloric caeca bud; re, rectum; snv, supranuclear vacuoles; st, stomach; u, urinary opening; vs, vitelline syncytium; y, yolk; ylm, yolk-like material; ys, yolk sac. Scale bar: (B-E) = 100 μm or (C, insert) = 50 μm; (F-Q) = 50 μm.