Assessment of Gill Pathological Responses in Yellowfin Sea Bream (Acanthopagrus Latus) Under Aeromonas Hydrophila Exposure

Abstract

<span>Bacterial diseases in cultured fish are considered the main problem with aquaculture system in Iran. The gills are multifunctional organs responsible for respiration, osmoregulation, nitrogenous waste excretion, and acid-base balance. Moreover, they are very sensitive to water contamination. <em>Aeromonas hydrophila</em> (<em>A. hydrophila</em>) is an opportunist pathogen responsible for a wide range of diseases in different species of fish. The gill histological alterations were used to assess the effects of <em>A. hydrophila</em> exposure on yellowfin sea bream, <em>Acanthopagrus latus</em> (<em>A. latus</em>). In this regard, 90 <em>A. latus</em> were exposed to the concentrations of <em>A. hydrophila</em> (10³ and 10⁶ CFU/ml) for three weeks. The most histopathological alterations in the gill of the exposed fish included hypertrophy and hyperplasia of the epithelial cells, lamellar fusion, club shaping of gill lamellae, lifting of the epithelium and edema of lamellae with large sub-epithelial space, blood congestion, and hypertrophy and hyperplasia of the mucosal cells. The histopathological alterations were observed in the gill of fish exposed to higher levels of <em>A. hydrophila </em>(10⁶ CFU/ml) consisted of aneurysm and hemorrhage with blood congestion. According to the obtained results of this study, <em>A. hydrophila </em>could cause severe histopathological changes in the gill of <em>A. latus </em>and decrease gas change capability in yellowfin sea bream. Furthermore, the findings of the present study suggested that histopathological changes of the gill provide helpful information about the environmental conditions and as particular biomarkers may help the evaluation of fish general health.</span>