Low temperature-induced variation in plasma biochemical indices and aquaglyceroporin gene expression in the large yellow croaker Larimichthys crocea

Low temperature influences multiple physiological processes in fish. To explore the adaptability of the large yellow croaker (Larimichthys crocea) to low temperature, the concentrations of glycerol, blood urea nitrogen (BUN), and triglycerides (TG) in plasma, as well as the expression levels of metabolism-related genes aqp7 and aqp10, were measured after exposure to low temperature stress and during subsequent rewarming. In addition, tissue samples from the intestine and liver were histologically analyzed. We found that the concentrations of plasma glycerol, BUN, and TG, decreased under low temperature stress, suggesting the metabolism of fat and protein slowed at low temperature. The expression levels of aqp7 and aqp10 mRNA were also downregulated under exposure to low temperature. Interestingly, above plasma indices and gene expression returned to basic levels within 24 h after rewarming. Furthermore, the liver and the intestine were damaged under continuous low temperature stress, whereas they were repaired upon rewarming. From the above results, we concluded that aqp7 and aqp10 genes were sensitive to low temperature, and that the decrease in their expression levels at low temperature might reduce energy consumption by L. crocea. However, the adaptation to low temperature was limited because the key metabolic tissues were damaged under continuous exposure to low temperature. Interestingly, the metabolism of L. crocea was basically back to normal within 24 h of rewarming, showing that it has high capacity of self-recovery.