en تخصصي Special پژوهشي Research <strong>Background:</strong> Bacterial diseases in cultured fish are considered the main problem to aquaculture system. Skin is the structure that covers the body in fish. Skin histopatological alterations were used to assess the effects of <em>Aeromonas hydrophila</em> exposure on the yellowfin seabream <em><span dir="RTL">)</span>Acanthopagrus latus<span dir="RTL">(</span></em>.<br> <strong>Methods:</strong> In this regard, 90 <em>A. latus</em> were exposed to sublethal concentrations of <em>A. hydrophila</em> (10³,10⁶ CFU/ml) for 3 weeks.<br> <strong>Results:</strong> Some more severe alternations found in the skin of fish exposed. The most frequent histopathological changes detected in the skin including hyperplasia of epidermis, hypertrophy and hyperplasia of the mucosal cells and dermis edema. Some more severe alternations found in the skin of fish exposed to higher level of <em>A. hydrophila </em>(10⁶ CFU/ml) included telangiectasia of dermis layer. In addition, according to the results of histometrical studies in treated fish compared to control group showed that thickness of epidermis and dermis layers were increased significantly (<em>P</em><0.05).<br> <strong>Conclusion:</strong> <em>A. hydrophila </em>can cause major histophatological changes in the skin of <em>A. latus</em>. In addition, histopathological changes of the skin provide helpful information about the environmental conditions and as particular biomarkers may provide imminent into evaluating the general health and stress status of fish. Hispathology, Skin, Acanthopagrus latus, Aeromonas hydrophila Acanthopagrus Latus, Aeromonas Hydrophila, Hispathology, Skin 1 5 http://ijt.arakmu.ac.ir/browse.php?a_code=A-10-479-1&slc_lang=en&sid=1 Fatemeh Azadbakht f.azadbakht6776@gmail.com 10031947532846006732 10031947532846006732 Yes Department of Marine Biology, Faculty of Marine Science, Khorramshar University of Marine Science and Technology, Khorramshar, Khouzestan, Iran. Solmaz Shirali 10031947532846006733 10031947532846006733 No Department of Marine Biology, Faculty of Marine Science, Khorramshar University of Marine Science and Technology, Khorramshar, Khouzestan, Iran. Mohammad Taghi Ronagh 10031947532846006734 10031947532846006734 No Department of Marine Biology, Faculty of Marine Science, Khorramshar University of Marine Science and Technology, Khorramshar, Khouzestan, Iran. Issac Zamani 10031947532846006735 10031947532846006735 No Department of Marine Biology, Faculty of Marine Science, Khorramshar University of Marine Science and Technology, Khorramshar, Khouzestan, Iran.