The aim of this study was to test whether temperature acclimation (10 vs 20 °C) effects on tissue
glycogen content,
hypoxia tolerance, and swimming performance of Chinese crucian carp (Carassius auratus) varied with seasonal acclimatization (winter vs spring) and potential combined interactions. Both the routine metabolic rate (MO(2rout)) and critical
oxygen tension (P(crit)) of the MO(2rout) increased significantly with temperature, whereas the seasonal acclimatization showed no significant effect. Only the high temperature group that acclimatized in spring showed a significantly higher aquatic surface respiration (ASR(crit)) value compared with the other three groups. Fish in spring tended to show ASR behavior at higher
oxygen tension compared with those in winter, which might have been caused by a more active lifestyle. Time to show LOE prolonged by 25-34% under low temperature. Spring fish showed 20% shorter LOE duration
at 10 °C, whereas the difference tended to vanish at 20 °C.
Glycogen contents in both liver and muscle were higher in winter than spring. The liver and muscle
glycogen content decreased by 5-42% after exposure to anoxic conditions, whereas the magnitude was much smaller in spring. When fish swam in normoxic conditions, fish in higher temperatures showed higher critical swimming speed (Ucrit) than low temperature (5.49 vs 3.74 BL s(-1) in winter and 4.27 vs 3.21 BL s(-1) in spring), whereas fish in winter also showed higher U(crit) than fish in spring for each temperature. However, when fish swam in hypoxic waters, fish in higher temperatures showed a more profound decrease (52-61%) in U(crit) compared to those in lower temperature (25-27%). Fish in lower temperatures that had acclimatized in winter showed the highest U(crit), which might have been caused by higher
glycogen storage. The present study suggested that both
glycogen storage and alterations in lifestyle had profound effects on
hypoxia tolerance and swimming performance, which resulted in a profound difference between seasons and acclimation temperatures.