Burmese Pythons and their wondrous stomachs!
The Burmese Python, a constrictor snake notably found naturally in Southeast Asia, with a large invasive population in Florida, is an apex predator that can grow on average 16 feet (ca. 5 m) in length (Smithsonian’s National Zoo and Conservation Biology Institute, n.d.). As a snake without venom, these creatures will eat their meals whole after killing them through asphyxiation. With such a large meal, it can supply the body with enough nutrients to not eat for many days. Many of these days are spent digesting their food. These wondrous creatures are able to do this due to the extreme plasticity of their intestines. Intestine plasticity is the ability of the intestines and its cells to undergo morphological changes as well as functional changes (Melo & Sauvage, 2019). Specifically, the Burmese Python’s small intestines double in mass after just 24 hours of consumption (Andrew et al., 2015). Additionally, microvilli of the simple columnar epithelium of the small intestines will increase in length up to six times (Andrew et al., 2015). These changes help with the absorption and movement of the food through the digestive tract.
While the extreme intestinal plasticity explains how the Burmese Python can digest such a large meal, it does not explain how they are able to handle the large amounts of some nutrients or minerals that come with eating such a large prey. More precisely, how do these animals process the large amount of calcium and phosphorous that can come from digesting the skeleton? The two hormones that regulate the uptake and release of these two minerals are calcitonin and parathyroid hormone (Shaker, 2023). Calcitonin and parathyroid hormone work inversely to one another to maintain homeostasis of calcium and phosphorus levels (Shaker, 2023). Calcitonin reduces calcium by inhibiting the absorption of it in the intestines and kidneys as well as slowing the activity of osteoclasts that break down bone tissue, increasing calcium levels in the blood stream (Shaker, 2023). Parathyroid hormone increases calcium levels by promoting activity of osteoclasts and absorption of calcium by the intestines and kidneys (Shaker, 2023). Parathyroid hormone and calcitonin work similarly to maintain homeostasis of phosphorus (Shaker, 2023). For Burmese Pythons, they have a third method to regulate levels of phosphorus and calcium. Once the prey is eaten, the plasticity of the intestines changes certain cells into specialized cells that can intake excess calcium and phosphorous and collect it in crypts for the disposal later in their feces (Lignot et al., 2025).
The observation of these phenomena in Burmese Pythons was possible through electron microscopy and Energy-Dispersive X-Ray (EDX) analysis. EDX is done by firing an incident electron beam at the tissue being studied (Scimeca et al., 2018). Once this beam reaches the atoms of the tissue, it causes elastic and inelastic scattering of electrons (Scimeca et al., 2018). This ionizes the atom, which in turn, will fire back an x-ray that has the same energy as the difference of separation-energy between the outer and inner shell of the atom that it was fired upon (Scimeca et al., 2018). Matching the energy levels of these x-rays to known energy levels of elements confirms what elements the tissue consists of (Scimeca et al., 2018). For the Burmese Python, this could locate crypts with large amounts of calcium and phosphorus in them.
Burmese Pythons have very recently been discovered to have specialized cells capable of storing and excreting excess calcium and phosphorous. These specialized cells have apical crypts or divots within the epithelial tissue of the intestinal tract. When the Burmese Python intakes a large meal after killing it, their body morphologically changes and acquires these specialized cells. During digestion, excess calcium and phosphorous get stored in the crypts of these animals to be expelled at a later date. When conducting the research for this, the researchers tested their hypothesis through deliberately feeding different Burmese Pythons different meals. Specifically, they analyzed Burmese Pythons that fasted, Burmese Pythons that were fed normally with rats, Burmese Pythons that were fed a boneless diet, and Burmese Pythons that ate a boneless diet but were also fed calcium carbonate, a calcium-rich supplement (Lignot et al., 2025). When the researchers observed the Burmese Pythons during their digestion phase, they saw various things occurring. First, in the fasting snakes and snakes that had a boneless diet, they saw no calcium or phosphorous within the intestinal crypts. However, for the snakes that either were normally fed or had a calcium-rich supplement, they found large particles of calcium and phosphorous within these snakes.
The crypts are depicted as small pits that are bulbous within the intestinal tract. They have dense microvilli on the outside of the crypt prior to the entrance. However, once in the crypt, the microvilli are less dense and less developed. In crypts where the snakes were not fed calcium or phosphorous, they maintained their light bulb shape. However, in those snakes that had meals dense with calcium and phosphorous, the lining of the crypt would expand to accompany a large particle within it (Starr, 2025). These large particles found in the crypts of the intestinal tract contained traces of calcium, phosphorous and iron. The different masses of each of these substances caused these particles to form multiple layers. Iron was found to be in the centre of the particles, followed by phosphorous and finally calcium.
Although the crypts serve as an excellent way for these snakes to regulate high levels of calcium and phosphorous in the body. Like many other animals, snakes also use a combination of hormones to maintain homeostasis of calcium and phosphorous. These two hormones that are primarily responsible for calcium and phosphorous homeostasis are Parathyroid Hormone (PTH) and calcitonin. PTH forms in the parathyroid gland as a 115 amino acid polypeptide that is not yet active. It is cleaved twice down to 84 amino acids where it becomes active (Khan et al., 2022). PTH regulates calcium by stimulating osteoblasts to express receptor activators responsible for converting osteoblasts to osteocytes (Khan et al., 2022). They also inhibit osteoprotegerin, allowing improved production of osteoclasts to break down bone to supply the body with calcium and phosphorous (Khan et al., 2022). Thyroid parafollicular cells release calcitonin when there are high levels of calcium and phosphorus in the body. Calcitonin decreases the level of calcium in the body by stimulating osteoblasts to deposit calcium and phosphorus while also increasing the absorption of calcium and phosphorus in the kidneys so that it can be excreted out (Yu & Sharma, 2023). When looking at Burmese Pythons on these specific diets, snakes that were fasting or had calcium deficient diets had notable signs of PTH and calcitonin increase, suggesting that the body was trying to maintain homeostatic conditions with the scarce availability of calcium in their diet (Lignot et al., 2025).
Although these researchers continually stated that these intestinal crypts were new cell types within the Burmese Python, I believe that this statement was not accurate. The morphological change that these animals go through is what causes the intestinal tract to interfold, creating these intestinal crypts using the epithelial tissue that lines the intestinal tract along with other progenitor cells that will differentiate into necessary cells to conduct the collection of calcium, phosphorus, and iron into the crypts (Sumigray et al., 2018). This is similar to the way the crypts of our intestinal tract form, though they do not have the same function. What causes the calcium, phosphorus, and iron to collect in these crypts is unknown and could be the path to understanding the mechanism behind how these large particles form.
References:
Andrew A. L., Card D. C., Ruggiero R. P., Schield D. R., Adams R. H., Pollock D. D., Secor S. M., & Castoe T. A. (2015). Rapid changes in gene expression direct rapid shifts in intestinal form and function in the Burmese python after feeding. Physiological Genomics, 47(5), 147-157. 10.1152/physiolgenomics.00131.2014
Deftos L., & Shaker J. (Publication_Date). Calcium and Phosphate Homeostasis – Endotext – NCBI Bookshelf. Publication_Title, https://www.ncbi.nlm.nih.gov/books/NBK279023/
de Sousa e Melo F., & de Sauvage F. J. (2019). Cellular Plasticity in Intestinal Homeostasis and Disease. Cell Stem Cell, 24(1), 54-64. 10.1016/j.stem.2018.11.019
Lamsira H., Bischetti S., IRCCS San Raffaele R., Rome O., Department of Biomedicine and Prevention U. o. R. “. V., Scimeca M., Italy D., Bonfiglio R., & Bonanno E. (Publication_Date). Energy Dispersive X-ray (EDX) microanalysis: A powerful tool in biomedical research and diagnosis – PMC. Publication_Title, https://pmc.ncbi.nlm.nih.gov/articles/PMC5907194/
Lignot J., Pope R. K., & Secor S. M. (2025). Diet-dependent production of calcium- and phosphorus-rich ‘spheroids’ along the intestine of Burmese pythons: identification of a new cell type?. Journal of Experimental Biology, 228(14), Page. 10.1242/jeb.249620
Schield D., Alabama D., Card D., Ruggiero R., and D., Adams R., Texas; D., Castoe T., Pollock D., Andrew A., & Secor S. (Publication_Date). Rapid changes in gene expression direct rapid shifts in intestinal form and function in the Burmese python after feeding – PMC. Publication_Title, https://pmc.ncbi.nlm.nih.gov/articles/PMC4421790/
Starr M. (2025, July 9). New Cell Discovered in Pythons Allows Them to Completely Digest Bones. ScienceAlert, https://www.sciencealert.com/new-cell-discovered-in-pythons-allows-them-to-completely-digest-bones