Essay #1

Intestinal plasticity is the ability of the digestive tract to change its size, thickness, and function in response to physiological demands. This typically occurs in sit-and-wait predators, like the Burmese python , the python is able to fast for weeks to months and then ingest a large prey. While fasting their intestines shrink, which reduces the metabolic cost related to maintaining digestive tissue. When feeding the pythons intestine goes through hypertrophy, this is when the intestine doubles in mass boosting the nutrient transport rate to efficiently digest and absorb the nutrients. The intestine also sends out specialized cells to aid in digestion and absorbing the skeleton, processing the excess calcium and phosphorus to avoid toxicity. This process changes more than just the structure of the intestine but it also increases enzymatic activity, blood flow, and nutrient transporter expression. This whole ordeal shows how close the relationship between physiological and ecological strategy is. It also highlights how energy efficiency is optimized in animals with intermittent feeding habits (Secor & Diamond, 1998).
The ability to adjust internal systems in response to external demands is evident in vertebres regulation of mineral homeostasis particularly calcium and phosphorus levels. Parathyroid hormone (PTH) and calcitonin are two major hormones that regulate calcium and phosphorus acting as a physiological antagonists to maintain homeostasis. PTH is produced by the parathyroid glands in response to low calcium levels, this then stimulates the release of calcium and phosphorus from the bones into the bloodstream. The PTH also increases calcium absorption and decreased phosphorus reabsorption into the kidney, leading to a higher blood calcium and lower blood calcium, it does this through the activation of vitamin D. Together these hormones function as an antagonistic system. They illustrate the precise endocrine mechanisms organisms employ to sustain homeostasis, ensuring skeletal integrity, efficient muscle contraction, and proper neural signaling (Song, 2017). The dynamic changes in intestinal plasticity mirror this principle of physiological responsiveness this shows that organisms rely on multiple coordinated systems to survive in a forever changing environment.
Being able to understand these adaptations at the cellular level requires advanced tools capable of linking structure and function. Electron microscopy is an advanced imaging technique that uses a beam of electrons instead of light to visualize biological samples at extremely high resolution. EDX (Energy-Dispersive X-ray) analysis is an add-on technique used with electron microscopes to determine the elemental composition of samples, it also allows for the identification and quantification of elements within biological samples. EDX detects characteristics by hitting the specimen with an electron beam. The process consist of Exciting atoms in the specimen with the electron beam, collecting emitted X-rays using detectors, and analyzing X-ray energies to assign specific elements present in the sample. This process makes it possible to measure elements like calcium, phosphorus and trace metals. This whole process of imaging and element analysis is important for biological processes like bone mineralization, tissue remodeling, and nutrient absorption. By being able to connect structural observations to chemical composition scientist can better understand physiological systems (Thompson et al., 2016).
In conclusion, these topics reveal how organisms respond to environmental challenges, maintain internal balance, and how researchers are able to study these processes using advanced tools. The Burmese python’s ability to rapidly remodel its intestine, the precise hormonal control of calcium and phosphorus, and the visualization of elemental composition in tissues all underscore the complexity of life at both the structural and molecular level. Understanding these systems provides insight into the strategies organisms use to survive illustrating the connections between physiology and biochemistry.
 
References
Secor S. M., & Diamond J. (1998). A vertebrate model of extreme physiological regulation. Nature, 395(6703), 659-662. 10.1038/27131
Song L. (2017). Calcium and Bone Metabolism Indices. Advances in Clinical Chemistry, Volume 1, 1-46. 10.1016/bs.acc.2017.06.005
Thompson R. F., Walker M., Siebert C. A., Muench S. P., & Ranson N. A. (2016). An introduction to sample preparation and imaging by cryo-electron microscopy for structural biology. Methods, 100, 3-15. 10.1016/j.ymeth.2016.02.017

Essay #2

Burmese pythons is an interesting type of snake because of its digestive systems and how fast its able to switch between fasting and feeding. Pythons can go weeks without food then eat an entire prey in one meal. Because of how rapidly their intestines grow after feeding scientist use them for research on digestion and nutrient absorbing. An article by Lignot, Pope, and Secor (2025) studied the pythons intestinal cells to see how different types of diets can affect calcium regulation in the body. During the study the researchers found unusual calcium and phosphorus rich spheroids in the intestines of the fed pythons. They believed that these pythons might have and unknown intestinal cell type. In another article by Starr (2025) in Nature stated how these cells allow pythons to completely digest the skeletons of their prey.
When the python is fasting its intestinal tissue looks inactive and the epithelial lining forms a thin pseudostratified layer. Also while fasting the microvilli are short and atrophied. In figure 1A of the article the intestinal surface looks flattened and the empty crypts are easily visible, this tells us that during fasting the intestine is basically shut down. Once the python eats a normal meal with bones and organs the intestine starts to change immediately. The epithelial cells become tall and filled with lipid droplets as the snake begins digesting and absorbing nutrients, the microvilli are long in order to increase absorption efficiency. It was within this layer that the researchers found a new kind of cell with an apical crypt containing a small particle (Lignot et al., 2025, Fig. 1D–E). These crypts looked different because they didn’t contain lipids like the other cells and they also appeared darker under the microscope. The particles within them stained positive with Alizarin Red S which is a dye that binds to calcium. This suggest that they were mineralized spheroids forming during digestion of calcium-rich food. (Starr, 2025) said they found no bone fragments in the pythons feces suggesting that they fully digest and metabolize their preys skeleton. When the pythons are feed boneless prey the crypts are still there but they lack calcium deposits. An elemental X-ray (EDX) analysis showed that the crypts contain iron, sulfur, and phosphorus, with little to no calcium present (Lignot et al., 2025, Fig. 3C–D). The enterocytes remain active, but without the minerals from the bones, they do not produce the same layered spheroids. This shows that the formation of these particles depends directly on dietary calcium availability. Feeding the pythons boneless prey but supplementing it with calcium carbonate did the opposite. All the crypts has calcium and phosphorus. The spheroids form multilayered structures with dense nucleation centers surrounded by acellular layers. These cells very narrow, have short microvilli, and feature an apical fold forming the crypt (Starr, 2025).
The crypt particles form soon after feeding. When looking at them under electron microscopy they look circular, layered spheroids with a dense central core. They are mainly composed of calcium, phosphorus, oxygen, and some iron this suggest that they have a role in mineral storage or regulation. These structures likely prevent dangerous spikes in blood calcium levels following bone digestion by temporarily sequestering excess minerals inside intestinal cells.
Just like in other verterbres the calcium balance is controlled by the hormones calcitonin and parathyroid hormone. During fasting the hormone levels remain low because there isn’t any calcium to regulate. After a normal feeding the calcium levels rise and so does the calcitonin because its helping to regulate absorption and deposition. On the other hand when the pythons are feed boneless prey instead of the calcitonin rising the PTH rises because its releasing calcium from the bone reserves to maintain homeostasis. These hormonal responses show how the python’s body can quickly adjust to either excess or deficiency in dietary calcium, maintaining stability through endocrine feedback.
In the article by Lignot the researchers proposed that the intestinal cells crypt cells represent a new epithelial cell type unique to bone-eating snakes. These cells lack lipid droplets, show no peroxidase activity, and contain mineralized spheroids that no other intestinal cells exhibit. Their specialized morphology suggests that there might be a distinct function related to mineral management. Starr (2025) notes that similar cells were later identified in other reptiles, including boas, anacondas, and Gila monsters, indicating that this adaptation may have evolved multiple times or be more widespread among species that swallow prey whole.
In conclusion, both of these articles proves that pythons have evolved a efficient digestive strategy. When they fast the intestine rest, when feeding they activate crypt cells that regulate mineral activity from the bones. These calcium- and phosphorus-rich spheroids act as temporary storage sites, protecting the snake from mineral overload while ensuring efficient digestion. The changing levels of calcitonin and PTH further highlight the python’s precise control over calcium metabolism.