Effect of acclimation temperature on thermoregulatory behaviour, thermal tolerance and respiratory metabolism of Lutjanus guttatus and the response of heat shock protein 70 (Hsp70) and lactate dehydrogenase (Ldh-a) genes

This study evaluated the effect of different environmental temperatures in the physiology of Lutjanus guttatus juveniles by analysing their thermoregulatory behaviour, thermal tolerance, oxygen consumption rates and thermal metabolic scope. Jointly, the effect of acclimation and critical temperatures on heat shock protein 70 (Hsp70) and lactate dehydrogenase (Ldh-a) gene expressions were also analysed using acclimation temperatures of 20, 23, 26, 29 and 32 degrees C. The results showed that the final preferred temperature in juvenile snapper was 26 degrees C with a thermal window of 336.5 degrees C2, which was related to an optimal temperature for their physiology determined by the routine metabolic rate and thermal metabolic scope. At temperatures from 20 to 26 degrees C, the routine metabolic rate and Hsp70 and Ldh-a genes had the lowest values related to a basal expression level. At acclimation temperatures from 29 to 32 degrees C and after critical thermal maximum (CTmax) limit, the relative expression of Hsp70 and Ldh-a genes increased significantly, but the main response at CTmax was the upregulation of Hsp70 gene.