Effect Of Temperature On The Metabolic Strategies Of Juvenile Southern Catfish (Silurus Meridionalis)

To estimate whether the effects of feeding on swimming performance vary with acclimation temperature and test the hypothesis that digestion has a more notable physiological effect at high temperature than low temperature in juvenile southern catfish (Silurus meridionalis), an ambush forager distributed along the JiaLing and Yangtze Rivers, China, we investigated the specific dynamic action (SDA), critical swimming speeding (Ucrit) and oxygen consumption rate (VO2) of fasting and feeding fish at acclimation temperatures of 15, 21, 27, and 33 oC.The results as follows:1. The pre-fed resting oxygen consumption rate (VO2rest) values increased significantly with temperature (p < 0.05). The VO2 increased significantly 2 h after feeding in every temperature group, then reached a plateau and decreased significantly to the pre-fed level. The peak time values were 27.14 h at 15 oC, 20.00 h at 21 oC, 13.43 h at 27 oC, and 14.00 h at 33 oC. The VO2peak increased with temperature (p < 0.05), whereas the factorial metabolic scope did not significantly differ among the four temperature groups. The SDA duration decreased from 65.43 to 40.29 h as the temperature increased from 15 to 33 oC (p < 0.05). The duration of SDA did not differ in temperatures ranging from 15 to 21 oC, but it increased as the temperature increased from 21 to 33 oC (p < 0.05). The SDA coefficient increased from 15 to 21 oC (p < 0.05), but there was no significant difference among 21, 27 and 33 oC.2. The Ucrit values were 2.18, 2.74, 3.69, and 3.67 BL s-1 at 15, 21, 27 and 33 oC, respectively. The Ucrit significantly increased in the temperature zone of 15 to 25 oC (p < 0.05), but there was no significant difference between 27 and 33 oC. The VO2 increased with an increase of the swimming speeds (U) at every acclimation temperature (p < 0.05). The active oxygen consumption rate (VO2active) were 101.4, 161.9, 240.0, and 265.2 mgO2 kg-1 h-1 at 15, 21, 27 and 33 oC, respectively. The VO2active increased with the increase of temperature (p < 0.05).3. The Ucrit of the feeding groups were 2.15, 2.41, 3.00, and 2.90 BL s-1 at 15, 21, 27 and 33 oC, respectively. There was no significant difference between the unfed and fed group at 15 oC (p = 0.66). However, Ucrit values of the feeding groups were 12.04, 18.70, and 20.98% lower than those of the fasting groups at 21, 27, and 33 oC, respectively (p < 0.05).4. The VO2rest values of the fasting groups were 25.43, 36.82, 43.72, and 54.22 mgO2 kg-1 h-1 at 15, 21, 27 and 33 oC, respectively, whereas the resting metabolic rates of the feeding groups in peak times were 49.7, 89.8, 127.6, and 163.5 mgO2 kg-1 h-1 at 15, 21, 27 and 33 oC, respectively. The VO2max values of the feeding groups were 128.1, 184.9, 273.7, and 237.9 mgO2 kg-1 h-1 at 15, 21, 27 and 33 oC, respectively. The VO2max values of all feeding groups were higher than those of the fasting groups at all temperature (p < 0.05).The indications as follows:1. The VO2max increased with increasing temperature, but the relative residual metabolic scope (VO2max-VO2peak) during swimming decreased with increasing in temperature. The present study showed that the impairment of postprandial swimming performance increased with increasing temperature due to the unparalleled changes in the catfish's central cardio-respiratory, peripheral digestive and locomotory capacities.2. The different metabolic strategies of juvenile southern catfish at different temperatures may relate to changes in oxygen demand, imbalances in ion fluxes and dissolved oxygen levels with changes in temperature.