Ultrastructural Alterations in the Gills of Labeo rohita Fingerlings Exposed to Thermal Extremes

This study aimed to determine the cellular alterations in the gill of Labeo rohita exposed to lethal temperature maxima (LTMax) and lethal temperature minima (LTMin) by means of transmission electron microscopy (TEM). Acclimation of advanced fingerlings of L. rohita was carried out at 26 degrees C for 30days. Acclimated fish were subjected to a constant rate of increase or decrease in temperature (0.3 degrees C/min) until the LTMax and LTMin values were reached. Dissected gills were processed for TEM, both at the end of acclimation period at ambient temperature (26 degrees C) and at lethal temperatures. Results indicated that at ambient temperature, the gill tissues appeared normal. However, significant changes were observed at lethal temperatures. The gill tissues at lethal temperature maxima showed severely damaged lamellae, with more vacuolated space. At lethal temperature minima, gill tissues showed increased density of mitochondria. Our prima-facie report indicated that L. rohita exposed to lethal temperatures exhibited marked ultrastructural changes in the gills.