Figure 1.

(A) An overview of the morphology of the gastrointestinal tract in Atlantic salmon. (B) A longitudinal section of the entire middle and posterior intestine from SW-acclimated salmon with higher magnifications shown as inserts. The brush border is visualized by staining for alkaline phosphatase activity with NBT/BCIP. Staining of the brush border (dark brown) is seen throughout the intestine, however, more intensely in the middle segment. Abbreviations: E, esophagus; L, liver; S, stomach; PC, pyloric caeca; MI, middle intestine; PI, posterior intestine; IV, ileo-rectal valve.