Integrated postprandial responses of the diamondback water snake, Nerodia rhombifer.

Among snakes, the magnitude to which intestinal performance is regulated with feeding and fasting is adaptively linked to their natural feeding frequency. For infrequently feeding boas and pythons, gastrointestinal form and function are widely regulated with each feeding bout. In contrast, snakes that naturally feed more frequently modestly regulate intestinal function with each meal. To further explore the postprandial responses of a frequently feeding snake and assess whether such responses are matched in magnitude, we examined the postprandial metabolic, morphologic, and functional responses of the diamondback water snake (Nerodia rhombifer) following the consumption of catfish meals equaling 25% of their body mass. After feeding, N. rhombifer experienced 5.4-fold increases in metabolic rate and a specific dynamic action of 101 kJ that equaled 25.3% of the ingested energy. Nerodia rhombifer that were fed did not undergo any change in stomach tissue mass but did experience a rapid drop in gastric pH and a decline in tissue stores of pepsinogen. Feeding triggered an increase in pancreatic mass and a temporary loss of trypsin activity. The small intestine of N. rhombifer responded to feeding with a 70% increase in mass and a 27% increase in enterocyte length but no change in microvillus length. Intestinal nutrient uptake rates did not increase with feeding, whereas intestinal aminopeptidase-N activity increased by fivefold. The postprandial increases in metabolism and gastrointestinal morphology and function of N. rhombifer are of a lower magnitude than is characteristic of infrequently feeding snakes and are more similar to the responses observed for other frequently feeding species. In support of an adaptive interplay between feeding habits and digestive physiology, this study demonstrates that the regulation of gastrointestinal structure and function for the frequently feeding N. rhombifer is generally modest and matched in magnitude.