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First published online January 8, 2007
Journal of Experimental Biology 210, 340-356 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.02626

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Adaptive regulation of digestive performance in the genus Python

Brian D. Ott^* and Stephen M. Secor

Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL 35487-0344, USA

View larger version (13K): [in this window] [in a new window]   Fig. 1. Photographs and relative body shape (body mass, Mb/total length, TL) of the five Python species used in this study. (A) P. brongersmai, (B) P. regius, (C) P. sebae, (D) P. molurus, (E) P. reticulatus. Note the significant variation in body shape from the short and stout P. brongersmai to the long and slender P. reticulatus. In the histogram, letters above bars that are different denote significant (P<0.05) differences between means, as determined from post hoc pairwise comparisons.

View larger version (13K): [in this window] [in a new window]   Fig. 2. Mean rates of oxygen consumption (O2) prior to day 0 and up to 10 days following the consumption of rodent meals equaling 25% of the snake body mass for Python brongersmai, P. molurus, P. regius, P. reticulatus and P. sebae (N=6-8 for each species). In this and the following figures, error bars indicate ± 1 s.e.m. and are omitted if the s.e.m. is smaller than the width of the symbol used for the mean value. Note the rapid increase in O2 following the consumption of a meal and a slower return to fasting rates by days 6-9.

View larger version (7K): [in this window] [in a new window]   Fig. 3. Percentage of ingested meal that was recovered within the stomach (A) and small intestine (B) of Python brongersmai, P. molurus, P. regius, P. reticulatus and P. sebae 2 days after the consumption of rodent meals equaling 25% of their body mass (N=3 for each species). There was significant variation in the percentage of the ingested meal remaining within stomachs among the species, as both P. brongersmai and P. regius had more of the meal still remaining than P. reticulatus and P. sebae. By contrast, there was no variation in the percentage of the ingested meal left in the small intestine. In A, letters above bars that are different denote significant (P<0.05) differences between means as determined from post hoc pairwise comparisons.

View larger version (27K): [in this window] [in a new window]   Fig. 4. Uptake rates of the amino acids L-leucine and L-proline and of the sugar D-glucose by the anterior (A) and distal (D) portions of the small intestine of fasted (following a 30-day fast, open bars) and fed (2 days postfeeding, solid bars) Python brongersmai, P. molurus, P. regius, P. reticulatus and P. sebae. All species (with the exception of P. brongersmai for L-leucine and L-proline) showed significant postprandial increases in nutrient uptake by the anterior small intestine and in many cases by the distal intestine. *P<0.05, **P<0.01, ***P<0.001.

View larger version (10K): [in this window] [in a new window]   Fig. 5. Aminopeptidase-N activity of the anterior (A) and distal (D) portions of the small intestine of fasted (following a 30-day fast, open bars) and fed (2 days postfeeding, solid bars) Python brongersmai, P. molurus, P. regius, P. reticulatus and P. sebae. There were significant postprandial increases in aminopeptidase-N activity of the anterior small intestine in all species, and the distal small intestine in three species; *P<0.05, **P<0.01, ***P<0.001.

View larger version (35K): [in this window] [in a new window]   Fig. 6. Small intestinal mass and length of fasted (following a 30-day fast, open bars) and fed (2 days postfeeding, solid bars) Python brongersmai, P. molurus, P. regius, P. reticulatus and P. sebae. All five species had significant postfeeding increases in small intestinal mass, whereas only P. reticulatus showed an increase in intestinal length with feeding. The photographs of small intestines of fasted and fed P. molurus illustrate the postprandial trophic response. Asterisks indicate significant differences between the two states; *P<0.05, **P<0.01.

View larger version (43K): [in this window] [in a new window]   Fig. 7. Width of the intestinal muscularis/serosa and mucosa layers, and height, width and volume of intestinal enterocytes and micrographs of the intestinal epithelium of fasted (following a 30-day fast, open bars) and fed (2 days postfeeding, solid bars) Python brongersmai, P. molurus, P. regius, P. reticulatus and P. sebae. Note that after feeding there is a lack of change in muscularis/serosa layer thickness and enterocyte height, and the significant increase in thickness of the mucosal layer and enterocyte width and volume. Asterisks indicate significant differences between the two states; *P<0.05, **P<0.01, ***P<0.001.

View larger version (27K): [in this window] [in a new window]   Fig. 8. Small intestine uptake capacities of L-leucine, L-proline and D-glucose. and intestinal aminopeptidase-N activity of fasted (following a 30-day fast, open bars) and fed (2 days postfeeding, solid bars) Python brongersmai, P. molurus, P. regius, P. reticulatus and P. sebae. After feeding, all five Python species significantly increased uptake of each nutrient and aminopeptidase-N activity; *P<0.05, **P<0.01, ***P<0.001.

View larger version (7K): [in this window] [in a new window]   Fig. 9. Standard metabolic rate (SMR) at 30°C plotted against body mass Mb for seven species of frequently feeding snakes and 11 species of infrequently feeding snakes. Interspecific allometric equations were generated from least-squares regression analysis of data from Secor and Diamond (Secor and Diamond, 2000), this study, and our unpublished observations. Numbers signify the following species: 1, Thamnophis marcianus; 2, Thamnophis sirtalis; 3, Lampropeltis getula; 4, Coluber constrictor; 5, Masticophis flagellum; 6, Nerodia rhombifer; 7, Pituophis melanoleucus; 8, Morelia spilota; 9, Crotalus cerastes; 10, Lichanura trivirgata; 11, Acrantophis dumerili; 12, Boa constrictor; 13, Python sebae; 14, P. regius; 15, P. molurus; 16, P. reticulatus; 17, P. brongersmai; 18, Eunectes murinus. Note that across the range of body masses compared, infrequently feeding snakes have SMR that are almost 50% less than those of frequently feeding species.