Patterns of blood flow during the postprandial response in ball pythons, Python regius

IntroductionThe integration of a species' ecology and physiology is exemplified in the adaptive interplay between their feeding ecology and digestive physiology (Karasov and Diamond, 1988;McWilliams et al., 1997;Secor, 2005a). A well-known example of this is the adaptive correlation between food habits (i.e. herbivory and carnivory) and the morphology and function of the gastrointestinal (GI) tract. The GI tract of herbivores is typically longer than that of carnivores and possesses specialized regions for the fermentation of plant material (Stevens and Hume, 1995;Karasov and Hume, 1997;Mackie, 2002). Equally apparent is how organisms are able to face routine fluctuations in the amount and type of food consumed due to seasonal changes in food availability, ontogenetic shifts in diet, reproductive status and alternating foraging and feeding strategies (O'Brien et al., 1989;Stergiou and Fourtouni, 1991;Koertner and Heldmaier, 1995;Johnson et al., 2001). In response to such shifts in feeding habits, and thus digestive demand, species modulate gut performance to match pace with digestive load (Hammond and Diamond, 1994;Piersma and Lindström, 1997;Weiss et al., 1998). The plasticity of GI performance is manifested in morphological restructuring and/or functional regulation at the cellular level (Ferraris, 1994;Carey, 1990;Secor, 2005a).The adaptive capacity to regulate digestive performance in response to changes in digestive demand is well expressed by amphibian and reptile species that naturally experience long episodes of fasting (Secor, 2005a). Anurans that estivate during dry seasons and snakes that employ the sit-and-wait tactic of foraging, and thus eat infrequently, severely downregulate GI performance upon the completion of digestion, maintain a quiescent gut while fasting, and with feeding, rapidly upregulate digestive performance (Secor and Diamond, 2000;Secor, 2005b). The benefit of this trait is observed as a reduction in energy expenditure during the bouts of fasting. For example, during estivation, the metabolic rates of anurans are depressed by 70%, and the standard metabolic rates (SMR) of sit-and-wait foraging snakes are 47% less than that of active foraging snakes that only modestly regulate GI performance with feeding and fasting (Guppy and Withers, 1999;Secor and Diamond, 2000).For sit-and-wait foraging snakes, the correlation between infrequent feeding and wide regulation of intestinal performance has been investigated for only four speciesThe adaptive interplay between feeding habits and digestive physiology is demonstrated by the Burmese python, which in response to feeding infrequently has evolved the capacity to widely regulate gastrointestinal performance with feeding and fasting. To explore the generality of this physiological trait among pythons, we compared the postprandial responses of metabolism and both intestinal morphology and function among five members of the genus Python: P. brongersmai, P. molurus, P. regius, P. reticulatus and P. sebae. These infrequently feeding pythons inhabi...

Section: Metabolic Responses To Feedingmentioning

confidence: 99%

Adaptive regulation of digestive performance in the genusPython

Ott

Secor

2007

“…Within 24 h of ingestion of a meal, a python's small intestine doubles in mass (Secor, 1995;Secor and Diamond, 1995;Lignot et al, 2005) and volume (Hansen et al, 2013), and increases its mass-specific lipid content by 75% (Henriksen et al, 2015). A portion of this increase in lipid content is caused by the accumulation of lipid droplets in the apical side of the enterocytes during the first day of digestion (Starck and Beese, 2001;Lignot et al, 2005;Starck and Wimmer, 2005;Helmstetter et al, 2009). It is generally believed that the meal is the primary source of these lipids (Holmberg et al, 2003;Starck and Wimmer, 2005;Secor, 2008;Henriksen et al, 2015), but this phenomenon has not been formally documented using any tracer methods.…”

Section: −1mentioning

confidence: 99%

“…A portion of this increase in lipid content is caused by the accumulation of lipid droplets in the apical side of the enterocytes during the first day of digestion (Starck and Beese, 2001;Lignot et al, 2005;Starck and Wimmer, 2005;Helmstetter et al, 2009). It is generally believed that the meal is the primary source of these lipids (Holmberg et al, 2003;Starck and Wimmer, 2005;Secor, 2008;Henriksen et al, 2015), but this phenomenon has not been formally documented using any tracer methods. A previous study showed that when pit-vipers were fed with mice that had been intravenously injected with [ 13 C]glucose and [ 15 N]leucine, the peak isotopic enrichments in the small intestine and the liver occurred between 48 and 96 h (McCue, 2007b).…”

Section: −1mentioning

confidence: 99%

“…The magnitude and timing of the SDA response in pythons depend on the relative size of the meal Diamond, 1997, 1998;Cox and Secor, 2007), the macronutrient composition of the meal (McCue et al, 2005;Enok et al, 2013;Henriksen et al, 2015), and body temperature (Bedford and Christian, 2000;Toledo et al, 2003;Wang et al, 2003). Nevertheless, under similar feeding conditions the SDA response is highly repeatable (Secor, 1995;Overgaard et al, 2002;Starck and Wimmer, 2005).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Digesting pythons quickly oxidize the proteins in their meals and save the lipids for later

McCue

Guzman

Passement

2015

Pythons digesting rodent meals exhibit up to 10-fold increases in their resting metabolic rate (RMR); this increase in RMR is termed specific dynamic action (SDA). Studies have shown that SDA is partially fueled by oxidizing dietary nutrients, yet it remains unclear whether the proteins and the lipids in their meals contribute equally to this energy demand. We raised two populations of mice on diets labeled with either [ 13 C]leucine or [ 13 C]palmitic acid to intrinsically enrich the proteins and lipids in their bodies, respectively. Ball pythons (Python regius) were fed whole mice (and pureed mice 3 weeks later), after which we measured their metabolic rates and the δ 13 C in the breath. The δ 13C values in the whole bodies of the protein-and lipid-labeled mice were generally similar (i.e. 5.7±4.7‰ and 2.8±5.4‰, respectively) but the oxidative kinetics of these two macronutrient pools were quite different. We found that the snakes oxidized 5% of the protein and only 0.24% of the lipids in their meals within 14 days. Oxidation of the dietary proteins peaked 24 h after ingestion, at which point these proteins provided ∼90% of the metabolic requirement of the snakes, and by 14 days the oxidation of these proteins decreased to nearly zero. The oxidation of the dietary lipids peaked 1 day later, at which point these lipids supplied ∼25% of the energy demand. Fourteen days after ingestion, these lipids were still being oxidized and continued to account for ∼25% of the metabolic rate. Pureeing the mice reduced the cost of gastric digestion and decreased SDA by 24%. Pureeing also reduced the oxidation of dietary proteins by 43%, but it had no effect on the rates of dietary lipid oxidation. Collectively, these results demonstrate that pythons are able to effectively partition the two primary metabolic fuels in their meals. This approach of uniquely labeling the different components of the diet will allow researchers to examine new questions about how and when animals use the nutrients in their meals.

“…In contrast to previous studies on digesting snakes, the postprandial tachycardia in our study was associated with a significant rise in MAP. However, because MAP did not increase proportionally to the rise in f H , and because stroke volume is likely to have been elevated, digestion was probably attended by a reduced total peripheral resistance as blood flow to the digestive organs increases during digestion (Secor et al, 2000a;Starck and Wimmer, 2005;Secor and White, 2010). In addition, lowering of Hct is likely to have reduced blood viscosity and hence could have alleviated the workload on the heart.…”

Section: Adrenergic and Cholinergic Cardiac Tone In Fasting And Posmentioning

confidence: 99%

Reduction of blood oxygen levels enhances postprandial cardiac hypertrophy in Burmese python (Python molurus)

Slay

Enok

Hicks

et al. 2013

Physiological cardiac hypertrophy is characterized by reversible enlargement of cardiomyocytes and changes in chamber architecture, which increase stroke volume and V · O2,max via augmented convective oxygen transport. Cardiac hypertrophy is known to occur in response to repeated elevations of O 2 demand and/or reduced O 2 supply in several species of vertebrate ectotherms, including postprandial Burmese pythons (Python bivittatus). Recent data suggest postprandial cardiac hypertrophy in P. bivittatus is a facultative rather than obligatory response to digestion, though the triggers of this response are unknown. Here, we hypothesized that an O 2 supply-demand mismatch stimulates postprandial cardiac enlargement in Burmese pythons. To test this hypothesis, we rendered animals anemic prior to feeding, essentially halving blood oxygen content during the postprandial period. Fed anemic animals had heart rates 126% higher than those of fasted controls, which, coupled with a 71% increase in mean arterial pressure, suggests fed anemic animals were experiencing significantly elevated cardiac work. We found significant cardiac hypertrophy in fed anemic animals, which exhibited ventricles 39% larger than those of fasted controls and 28% larger than in fed controls. These findings support our hypothesis that those animals with a greater magnitude of O 2 supply-demand mismatch exhibit the largest hearts. The 'low O 2 signal' stimulating postprandial cardiac hypertrophy is likely mediated by elevated ventricular wall stress associated with postprandial hemodynamics.