The present study, considered histopathological changes in the two fish species, Persian sturgeon Acipenser persicus and Stellate sturgeon Acipenser stellatus. The aim was to describe the different gill tissue changes in these two species of sturgeons. The prepared sections of gill were stained with haematoxylin and eosin (HE) and observed under a light microscope. According to the results of this case study, the important histological lesions observed in the gills of sturgeons were: (1) hyperplasia of secondary lamellar epithelium (2) epithelial lifting of secondary lamellae (3) leukocyte infiltration (4) hypertrophy of the respiratory epithelium (5) fusion of adjacent secondary lamellae and (6) lamellar aneurysm. Hyperplasia of secondary lamellar epithelium was the most frequent gill lesion and fusion of adjacent secondary lamellae as a result of hyperplasia, proliferation of epithelial cells or epithelial lifting and in some cases hypertrophy was the second frequent gill lesion.
