Gonadal degeneration in sub-adult male pejerrey (Odontesthes bonariensis) during exposure to warm water

High water temperature has been shown to cause germ cell death in teleost fish but little is known on the process of cell death. This study was conducted to examine the mechanism and dynamics of heat-induced gonadal cell death in pejerrey (Odontesthes bonariensis) sub-adult males. Gonads of fish that were reared under three different thermal regimes were examined by light microscopy (hematoxylin-eosin), fluorescence microscopy (acridine orange, AO), and biochemical analysis (caspase-3 activity). Increases in the number of AO-stained cells preceded by peaks of caspase-3 activity were observed only in heat-stress groups and in a temperature-dependent manner. The results of histological and biochemical analyzes are consistent with apoptosis as a possible cause of gonadal cell death in heat-stressed pejerrey males.