Effect of meal size on the postprandial metabolic response in Chinese giant salamander Andrias davidianus larvae

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The digestive physiological characteristics of Chinese giant salamander Andrias davidianus have not been reported in the existing literature, and improving our knowledge in this area could help in the artificial culture of the species. The effect of meal size on the specific dynamic action (SDA) of A. davidianus larvae was assessed in this study at a water temperature of 20°C. The Chinese giant salamander was fed by test diets at meal sizes of 0.5, 1, 2, 4, 8 and 12% of its body mass (4.41 ± 0.07 g), and the postprandial oxygen consumption rate (MO2) was measured at 2 h intervals until the rate returned to its preprandial level. Peak MO2 (MO2peak) increased with meal size but levelled off at larger meal sizes within the studied range (8-12% body mass). The factorial metabolic scope increased from 1.27 to 2.11 when meal size increased from 0.5 to 12%. Time to reach MO2peak was not affected by the relative meal size. The SDA duration increased from 8.89 to 47.33 h as the relative meal size increased from 0.5 to 12%. The amount of energy expended during SDA increased linearly with increasing meal size (R2 = 0.842, p < 0.001, n = 60). There was no significant difference in the SDA coefficient among the different relative meal size groups. These data suggest that (1) A. davidianus larvae increase their energy demands during digestion by prolonging the SDA duration rather than increasing the MO2peak as meal size increases, and (2) A. davidianus showed a smaller factorial metabolic scope in the process of digesting large meal sizes, which may be related to the limited MO2peak of the species.