P1.212 Wednesday, Jan. 4 Cardiac thermal plasticity in the longjaw mudsucker Gillichthys mirabilis JAYASUNDARA, N.*; SOMERO, G.N.; Stanford University; Stanford University email@example.com
An insufficient supply of oxygen under thermal stress is thought define thermal limits in aquatic animals including fish. In most fish venous blood provides oxygen to the hearts. Considering the already depleted Po2 in venous return, fish cardiac performance might be compromised when under a thermal stress. Thus heart function might play a key role in establishing thermal limits in fish. We investigated effects of temperature acclimation on cardiac function of a eurythermal goby fish, the longjaw mudsucker Gillichthys mirabilis. We measured heart rate, metabolic enzyme activity, hemoglobin content and the change in global protein expression in fish acclimated to 9oC, 19oC and 26oC. Heart rate measurements were recorded under an acute heat ramp until the fish reached their cardiac arrhythmia temperature (TA). Fish acclimated to 9oC for one month had a lower heart rate than 19oC and 26oC acclimated fish at their respective acclimation temperatures. Fish acclimated to higher temperatures were able to extend their TA by 7oC; however, there was no significant difference between 19oC and 26oC acclimated fish. Blood hemoglobin content increased significantly with acclimation temperature, from 35 g/L in 9oC fish to 60-80 g/L in 19oC and 26oC fish. Fish acclimated to 26oC showed a decrease in aerobic metabolism. Elevated anaerobic enzyme activities were detected at both 9oC and 26oC. Global proteomic analysis suggests a variation in protein expression across different acclimation temperatures. These results illustrate the phenotypic plasticity of G. mirabilis and suggest that this eurythermal species maximizes its ability to circulate O2 at 19oC, a temperature shown by behavioral studies to be close to the species’ preferred temperature.