Both avian and non-avian reptiles excrete excess nitrogen in solid form—colloquially called “urate”—as an evolutionary adaptation to promote water conservation. However, many open questions remain regarding the composition, structure, and assembly of these biogenic materials. In a new study, scientists from Georgetown University, the International Diffraction Data Center, the Chiricahua Desert Museum, and Georgia State University analyzed urate emissions from ball python (King Python) and 20 other reptile species and identified a smart and adaptable system that handles both nitrogenous waste and salts.
Thornton etc.. examined the solid urine of more than 20 species of reptiles. Image credit: Thornton etc.., doi: 10.1021/jacs.5c10139.
“Most living things have some sort of excretory system—after all, what goes in must come out,” the Georgetown University chemist said. Jennifer Swift and her colleagues.
“In humans, excess nitrogen in the form of urea, uric acid and ammonia is excreted in the urine.”
“But many reptiles and birds convert some of the same nitrogen-containing chemicals into solids, or urates, which the animals excrete through their cloacae.”
Scientists believe that this process may have arisen as a way to conserve water.
“Although the formation of crystals in urine is a potential evolutionary advantage for reptiles, it is a serious problem for humans,” the researchers say.
“When too much uric acid is present in a person’s body, it can harden into painful shards in the joints, causing gout, or in the urinary tract as kidney stones.”
In a new study, the authors examined how reptiles safely excrete crystalline waste by studying urate from more than 20 reptile species.
“This research was really inspired by the desire to understand how reptiles are able to safely excrete this material, in the hope that it could inspire new approaches to disease prevention and treatment,” Dr Swift said.
The microscope images showed that three species—ball pythons, Angolan pythons and Madagascar tree boas—produce urates made of tiny textured microspheres ranging from 1 to 10 micrometers wide.
X-ray studies showed that the spheres were composed of even smaller nanocrystals of uric acid and water.
In addition, scientists have discovered that uric acid plays an important role in converting ammonia into a less toxic solid form.
They suggest that uric acid may play a similar protective role in humans.
“Our analysis of urate produced by a range of squamate reptiles helps shed light on key aspects of the highly intelligent adaptive system they use to manage nitrogenous waste and salt,” the researchers said.
“By establishing dietary controls, understanding how storage and environmental aging can affect sample analysis, and benefiting from improvements in instrumentation, the current study provides a much more detailed understanding of the structure and function of biogenic urates.”
“How and where microspheres assemble remain open and intriguing questions, although the fact that they are produced by a diverse set of uricotelic species suggests a low-energy process likely optimized by similar selection regimes.”
“Recognizing that uric acid plays a role in ammonia management may have broader implications for human health, although clinical studies are needed to fully confirm this hypothesis.”
conclusions were published today in Journal of the American Chemical Society.
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Alyssa M. Thornton etc.. Uric acid monohydrate nanocrystals: an adaptable platform for nitrogen and salt management in reptiles. J. Am. chem. Socialpublished online October 22, 2025; doi: 10.1021/jacs.5c10139
