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First published online November 28, 2008
Journal of Experimental Biology 211, 3767-3774 (2008)
Published by The Company of Biologists 2008
doi: 10.1242/jeb.023754
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Digestive physiology of the Burmese python: broad regulation of integrated performance

Stephen M. Secor

Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL 35405, USA


Figure 1
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  		Fig. 1. (A) A Burmese python swallowing a laboratory rat which it had killed by constriction. (B) A Burmese python 24 h after consuming a rat meal greater than 50% of the snake's body mass. This snake had experienced further distension of its body after feeding due to the build up of gases within the ingested dead rat.

 

Figure 2
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  		Fig. 2. (A) Daily X-ray images of a python digesting a rat that was equal to 25% of the snake's body mass. At 1 day postfeeding (DPF), the rat's skeleton is completely intact within the python's stomach, whereas by day 6 the rat's skeleton has been completely broken down and passed into the small intestine. (B) The postprandial profile of gastric pH for Burmese pythons demonstrating the rapid drop in pH after feeding, the steady maintenance of a very acidic pH during digestion, and the rise in pH upon the completion of gastric digestion when acid production ceases. Error bars in B and subsequent figures represent ±1 s.e.m. Gastric pH profile redrawn from data presented in Secor (Secor, 2003Go).

 

Figure 3
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  		Fig. 3. Transmission electron micrographs illustrating the rapid postprandial lengthening of the python's intestinal microvilli, reaching a peak in length at 3 days postfeeding. After digestion is complete (after day 6), the microvilli shorten in length. Bar in images represent 1 µm.

 

Figure 4
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  		Fig. 4. Activities of the brushborder enzymes aminopeptidase-N (APN) and maltase, and uptake rates of the amino acid L-proline and the sugar D-glucose as a function of time postfeeding for the proximal region of the Burmese python's small intestine. For both proteins and simple sugars, pythons experience matched regulation of intestinal digestion and absorption. Enzyme activity profiles taken from Cox and Secor (Cox and Secor, 2008Go).

 

Figure 5
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  		Fig. 5. Images of the small intestine of similar-sized Burmese pythons fasted and at 2 and 10 days postfeeding (DPF). By 2 DPF, the intestine has increased in diameter due primarily to hypertrophy of the epithelial cells; a response that has reversed by 10 DPF.

 

Figure 6
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  		Fig. 6. Plasma concentrations of cholecystokinin (CCK), glucose-dependent insulinotropic peptide (GIP), glucagon and insulin as a function of time postfeeding for the Burmese python. The dramatic postprandial release into circulation of these regulatory peptides may serve to signal the upregulation of tissue structure and function. Profiles of CCK, GIP and glucagon redrawn from data presented in Secor et al. (Secor et al., 2001Go).

 

Figure 7
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  		Fig. 7. Hypothetical model of the cellular mechanisms involved in the postprandial lengthening of the python's intestinal microvilli and subsequent shortening of the microvilli once digestion is complete. In this scenario, structural proteins and vesicles of membrane sequestered within the cytoplasm during fasting rapidly migrate to the apical membrane with feeding and are inserted in place to further lengthen the existing microvilli. After digestion is complete, the components of the microvilli are either released into the lumen or return back to the cytosol for reuse.

 

Figure 8
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  		Fig. 8 The effects of meal size (% of snake body mass, A) and body temperature (B) on the postprandial profile of VO2 (ml h–1) for juvenile Burmese pythons. Increasing meal size generates a more elevated and prolonged metabolic response. With an increase in body temperature, the metabolic profile becomes narrower and higher. A and B redrawn from data presented in Secor and Diamond, and Wang et al., respectively (Secor and Diamond, 1997bGo; Wang et al., 2003Go).

 

Figure 9
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  		Fig. 9. Positron emission tomography (PET) images of a fasted and fed (1 day postfeeding) Burmese python. Snakes were injected with 2-[18F]fluoro-2-deoxyglucose prior to scanning. Bright areas signify regions experiencing high rates of glucose metabolism. The difference between the two images is actually greater given that the intensity of the fasted image had to be increased 1000-fold in order to view the entire snake.

 

Figure 10
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  		Fig. 10. Wet mass of the heart, pancreas, liver and kidneys plotted against time postfeeding for Burmese pythons fasted (0) and following the consumption of rodent meals equal to 25% of the snake's body mass. Feeding generates respective increases in wet mass of 40%, 94%, 106% and 72% for the heart, pancreas, liver and kidneys.

 

Figure 11
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  		Fig. 11. Transmission electron micrograph of python intestinal epithelium embedded with spherical particles composed of calcium and phosphate. It is hypothesized that the source of the calcium and phosphate is the degraded skeleton of the rodent meal (Lignot et al., 2005Go). The bar in the image represents 1 µm.

 

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© The Company of Biologists Ltd 2008