Xenobiotic metabolism modulation after long-term temperature acclimation in juveniles of Solea senegalensis

The Senegalese sole, Solea senegalensis, originates from subtropical waters and displays great adaptability to environmental factors such as temperature. A comprehensive study on the effect of long-term temperature acclimation on xenobiotic metabolism, along with the assessment of other parameters related to physiological status, was designed to characterize the response of this species to temperature fluctuations within a realistic range. S. senegalensis juveniles were acclimated for a period of 60 days to two different ambient temperatures, 15 and 20 A degrees C. Several hepatic, gill, muscular and plasmatic parameters were measured over time at the two temperatures. The lower temperature triggered, over time, the synthesis of hepatic microsomal cytochrome P450-related enzymes (e.g. 7-ethoxyresorufin O-deethylase (EROD), carboxylesterases, and the conjugating enzyme uridine diphosphate glucuronosyltransferase and, more significantly, EROD activity in gills. The antioxidant enzyme activities: catalase and glutathione reductase in liver were positively correlated to temperature. Plasmatic parameters (glucose, lactate, triglycerides and osmolality) were consistent with a good physiological status of the experimental fish. The expression of heat shock proteins in muscle did not significantly change in the two temperature groups. The results evidenced that the subtropical species S. senegalensis also uses the temperature compensation strategy to different degrees for most biotransformation enzymes; this response was more intense and faster in gills than in liver. This compensatory strategy did not apply to antioxidant enzymes and GST. The present findings highlight the need to consider the thermal history of the fish when using S. senegalensis as a sentinel in a biomarker-based pollution monitoring study. The fish plasticity on its strategy of physiological adaptation to temperature changes could contribute to explain the success in the geographical expansion of this species.