Avian and non-avian reptiles excrete excess nitrogen in solid form – colloquially called “urates” – as an evolutionary adaptation that contributes to water conservation. However, many questions remain open regarding the composition, structure and assembly of these biogenic materials. In new research, scientists from Georgetown University, the International Diffraction Data Center, the Chiricahua Desert Museum and Georgia State University analyzed the urate excretions of ball pythons (King of the Pythons) and 20 other reptile species and revealed an intelligent and highly adaptable system that manages both nitrogen waste and salts.
Thornton and others. studied the solid urine of more than 20 reptile species. Image credit: Thornton and others., doi: 10.1021/jacs.5c10139.
“Most living things have some sort of excretory system — after all, what goes in must come out,” said Jennifer Swift, a chemist at Georgetown University, and colleagues.
“In humans, excess nitrogen in the form of urea, uric acid and ammonia is excreted in the urine.”
“But many reptiles and birds package some of these same nitrogen-containing chemicals into solids, or urates, that the animals eliminate through their cloaca.”
Scientists believe this process may have evolved to conserve water.
“Although crystal formation in urine is a potential evolutionary advantage for reptiles, it is a serious problem for humans,” the researchers said.
“When too much uric acid is present in the human body, it can solidify into painful bursts in the joints, causing gout, or in the urinary tract as kidney stones.”
In the new study, the authors investigated how reptiles excrete crystalline waste safely, by studying urates from more than 20 reptile species.
“This research was really inspired by a desire to understand how reptiles are able to excrete this material safely, in the hope that it can inspire new approaches to disease prevention and treatment,” Dr Swift said.
The microscope images revealed that three species – ball pythons, Angolan pythons and Madagascar tree boas – produced urates made of tiny textured microspheres varying from 1 to 10 micrometers wide.
X-ray studies have shown that the spheres are made of even smaller nanocrystals of uric acid and water.
Additionally, scientists have discovered that uric acid plays an important role in converting ammonia into a less toxic solid form.
They think uric acid might actually play a similar protective role in humans.
“Our analysis of urates produced by a range of squamate reptiles serves to elucidate key aspects of the highly intelligent adaptable system they use to manage nitrogen waste and salt,” the researchers said.
“With dietary controls in place, an appreciation of how environmental storage and aging can affect sample analyzes and the benefits of advances in instrumentation, the current study provides a much more detailed understanding of the structure and function of biogenic urates.”
“How and where microspheres are assembled remain open and intriguing questions, although the fact that they are produced by a diverse set of uricotelic species suggests a low-energy process apparently optimized by similar selection regimes.”
“Recognition of the role of uric acid in ammonia management could have broader implications for human health, although clinical studies are needed to fully support this hypothesis.”
The results were published today in the Journal of the American Chemical Society.
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Alyssa M. Thornton and others. Uric acid monohydrate nanocrystals: an adaptable platform for nitrogen and salt management in reptiles. Jam. Chemical. Socpublished online October 22, 2025; doi: 10.1021/jacs.5c10139
