It may come as a surprise, but not all animals pee. While almost every living organism possesses an excretory system, most reptiles don’t eliminate excess nitrogen-containing waste in the form of liquid urine. Instead, they rid themselves of the chemicals by expelling them in the form of crystalline solids called urates.
Biologists believe reptiles evolved this unique system as a way to conserve water, but have long wondered how the urates don’t ultimately end up harming the animals. For humans, crystalline buildups in the body manifest as excruciating shards in joints—a condition known as gout—or as kidney stones in the urinary tract. Both conditions can become serious or even life-threatening when not treated properly.
For researchers, including Georgetown University chemist Jennifer Swift, analyzing reptilian pee crystals presented an opportunity to potentially improve or possibly save human lives. Their study, published on October 22 in the Journal of the American Chemical Society, offers some of the most detailed looks into reptile urates.
“This research was really inspired by a desire to understand the ways reptiles are able to excrete this material safely, in the hopes it might inspire new approaches to disease prevention and treatment,” Swift said in an accompanying statement.
Swift’s team used microscopic and X-ray imaging techniques to examine crystal samples from over 20 snake and lizard species. They found that at least three species—ball pythons (Python regius), Angolan pythons (Python anchietae), and Madagascan tree boas (Sanzinia madagascariensis)—produced urates featuring textured microspheres measuring anywhere from 1-to-10 micrometers wide.
X-ray analysis also revealed that these spheres contain even smaller nanocrystals composed of uric acid and water. They found that these small amounts of uric acid may help convert the reptiles’ accumulated ammonia into a less toxic, excretable solid form.
“Importantly, this points to a previously unrecognized physiologic function of uric acid, namely the ability to sequester ammonia by transforming it into a solid,” they write in their study.
Although more research is required, the team theorizes that in proper amounts, uric acid may actually have a surprising, similarly protective role in humans. Crystallized uric acid is still something no one wants in their body, but a better understanding of reptiles’ evolutionary urate solution may one day help develop new treatments for related human health complications.
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