Comparative histomorphology of epidermis of head and caudal peduncle in Otolithes ruber, Huso huso and Pangasius hypophthalmus fish

Three species of fish including, macroscopic scaled fish  as Otolithes ruber, microscopic scaled sturgeon as Huso huso and free scaled cat fish as  Pangasius hypophthalmus were prepared and specimen of dorsal of head and caudal peduncle were carried out. Routine procedures of tissues preparation followed and paraffin sections stained with (H&E) and (PAS). Results showed, epidermis formed non keratinized stratified squamous epithelium with epidermis, lymphocytes, goblet cells, taste bud and club cells. The epidermis thickness of the head skin was higher than that of the caudal peduncle, as demonstrated by image analysis using light microscopy. Goblet cells were along the superficial cells layers and their distributions were varied. In histomorphometric studies by PAS staining the highest number of these cells were seen in head of O. ruber and the lowest were seen in the caudal peduncle of P. hypophthalmus. Most of them were seen from the middle to surface layer of the epidermis. Club cells, with large nucleus, mostly evident in the deep and middle layer of the epidermis, being the largest cells within the epithelium. The highest numbers of these cells (61.8 ± 2.16) were found in head region of P. hypophthalmus. Taste buds as a sensory organ were not seen in caudal peduncle of O. ruber and H. huso. Based on the results of this study, epidermis had similarities in cell type and differences in their numbers that could be justified by the presence or absence of scales.