Histological changes in Horabagrus brachysoma acclimated to warm temperature and exposed to critical thermal maxima and minima

Abstract

Escalating concerns about global climate change necessitate investigations into its consequences for the survival of poikilothermic animals like fish. The present study describes histological alterations in gill, skin, kidney, liver, and brain tissues of the juvenile Horabagrus brachysoma specimens acclimated to 26°C (control) and 36°C for 30 days, and those exposed to dynamic temperature changes (increased or decreased at the rate of 0.3°C/min from 26°C), the critical thermal maxima (CTMax) and critical thermal minima (CTMin). The fish acclimated to 36°C and those exposed to CTMax (40.23 ± 0.12°C) and CTMin (14.15 ± 0.10°C) showed severe histological aberrations in gill, skin, liver, kidney, and brain tissues. Histological alterations in gill tissues included loss of epithelial cells in the branchial arch, thinning of the primary lamellae, and loss of the secondary lamellae. Thickening of the epithelial layer (36°C), and desquamation of epithelial cells (CTMax) were the histological alterations detected in skin tissues. Alterations in liver tissues included severe congestion with vacuolization and the cloudy appearance of cells and extensive loss of cellular contour. Extensive vacuolization with complete flattening of the tubule epithelial cells, distorted appearance of tubular lamellae, and marked loss of glomerular tuft were the changes recorded in kidney tissues. Brain tissue alterations comprised increased cellularity and vacuolization in the cerebrum (36°C), and nodular masses of various sizes in the cerebrum (CTMin). The present study showed that acclimation to warm temperature (36°C) and exposure to dynamic temperature changes (CTMax and CTMin) cause histopathological alterations in the vital organs of H. brachysoma. The findings of the present study can help in monitoring the health of H. brachysoma in the natural environment and in culture systems under a climate change scenario.