Meeting Abstract
Global warming is likely to intensify heat stress in marine and coastal organisms, affecting their development, growth, and reproductive functions. In this study, we performed histological observations on gonadal functions, immunohistochemical analyses of heat shock protein (HSP) and nitrotyrosine protein (NTP, an indicator of reactive nitrogen species, RNS) expressions, in situ TUNEL assay for cellular apoptosis, biochemical analyses of caspase-3/7 activity and protein carbonyl (PC, a measure of reactive oxygen species, ROS) contents, and coelomic fluid (CF, body fluid that regulates physiological functions) pH in the American oyster gonad with various water temperatures. Oysters were placed in six different twenty-gallon aquariums and exposed to control (24oC), medium (28oC), and high (32oC) temperatures under controlled laboratory conditions for one week. Higher temperature significantly decreased the number and diameter of eggs in ovary of female oysters and sperm cell growth, development, and production in male oyster’s. CF protein concentrations also declined compared to control temperature (24oC). In contrast, CF pH and HSP expression in gonad increased after heat-exposure, consistent with increased cellular apoptosis. The enhanced apoptosis in gonads of heat-exposed oysters was associated with increased gonad caspase-3/7 activity, PC contents, and NTP expression. Collectively, these results suggest that higher temperatures drastically increase ROS and RNS levels leading to increased cellular apoptosis, which subsequently decline gonadal functions in oyster.
