Comparative histology in the liver and spleen of three species of freshwater teleost

We describe and compare the histology of liver and spleen of Geophagus brasiliensis (Perciformes), Hypostomus francisci (Siluriformes) and Hoplias aff. malabaricus (Characiformes), tropical freshwater fishes. In G. brasiliensis and H. aff. malabaricus the hepatocytes were arranged in tubular form whereas in H. francisci they cord-like. In all species, hepatocytes presented glycogen, but in G. brasiliensis and H. aff. malabaricus they showed strong stained for hemossiderin in the cytoplasm. In G. brasiliensis and H. aff. malabaricus, melanomacrophage centres (MMCs) were associated to hepatic structures and only in G. brasiliensis was observed intrahepatic exocrine pancreas. The spleen, in all species, was characterized by red and white pulp without boundary between the two regions, but only in H. francisci was recorded nodular organization in splenic parenchyma. The G. brasiliensis and H. aff. malabaricus presented in the white pulp MMCs linked mainly to ellipsoids. Besides, we observed large MMCs in the spleen in relation to liver of G. brasiliensis and H. aff. malabaricus. In liver, highest values of reticular fibers and collagen were observed in G. brasiliensis. In spleen, highest values of reticular fibers and collagen were recorded in H. aff. malabaricus and H. francisci, respectively. Histological differences confirm the hypothesis that the phylogenetic distance is reflected in liver and spleen.