Irvine, Calif., July 1, 2026 — Stingrays are instantly recognizable creatures known for their graceful movements through coastal waters. However, hidden along their tails is one of nature’s most notorious defensive tools: a sharp, venomous spine. For humans, encounters with these spines can result in painful and potentially severe injuries. For predators, these spines can mean the difference between a successful hunt and a failed attack. Yet despite their importance, scientists have long known surprisingly little about why stingray spines vary so widely in shape from one species to another.
A new study published in Proceedings B offers fresh insight into this evolutionary puzzle. Led by PhD student Emily Poulin in the lab of Assistant Professor Christopher Martinez at the UC Irvine Charlie Dunlop School of Biological Sciences, the research shows that stingray spines reflect a delicate balance between various competing needs: the ability to puncture deeply, anchor in a predator’s flesh, resist breakage, or even break off when useful.
“Stingrays live in diverse habitats ranging from coastal oceans to the select rivers, like the Amazon,” said Poulin. “In these environments, they face very different predators, from sharks to river dolphins. We found that these differences are reflected in the shape and function of their defensive spines. Some species have spines that puncture deeply and may snap off inside a predator, while others have sturdier spines that are less likely to break and can be reused across multiple defensive encounters. The shape of a stingray spine can help reveal the evolutionary pressures a species has faced over tens of millions of years of predator-prey interactions.”
To uncover these patterns, the team studied spines from 30 stingray species, including both marine and freshwater rays. Because many of the specimens were rare and housed in museum collections, the researchers could not risk damaging them.
Poulin said the careful, preservation-minded approach was essential to the project’s success. “Many of the species we wanted to study are rare and represented by only a handful of specimens in museum collections,” she said. “Even when specimens were available, their defensive spines were often damaged or incomplete. Because these structures are irreplaceable, we could not simply test them by breaking or damaging them. Instead, we used high-resolution micro-CT scans to create digital and physical models that allowed us to study how the spines function while preserving the original specimens.”
The findings point to nature’s remarkable ability to solve problems through different evolutionary strategies. Some stingrays appear to rely on slimmer spines that can pierce deeply and potentially break off, giving the animal a chance to escape. Others, including many freshwater species, have stronger spines that may be better suited for repeated use.
Beyond stingrays, the study could help scientists better understand how defensive structures evolve across the animal kingdom, from porcupine quills to insect stingers. It may also inspire new designs for medical tools, protective materials or technologies that need to balance sharpness, strength and durability.
The work also highlights the value of museum collections, modern imaging, and collaboration across institutions. Future research, Poulin said, will need to look more closely at the predators stingrays face in the wild. “One of the biggest unanswered questions is how different predators influence the evolution of stingray defenses,” she said. “Integrating these approaches will help us better understand how animals adapt to the challenges of surviving and avoiding predation.”
As oceans and freshwater ecosystems face mounting pressures, studies like this underscore the importance of protecting biodiversity and supporting the research collections that help scientists understand it. Continued investment in natural history museums, imaging technology and ecological research will be essential for revealing how life adapts — and for applying those lessons to a more sustainable future.
About the University of California, Irvine Charlie Dunlop School of Biological Sciences:
Recognized for its pioneering research and academic excellence, the Charlie Dunlop School of Biological Sciences plays a crucial role in the university’s status among the nation’s top 10 public universities, as ranked by U.S. News & World Report. It offers a broad spectrum of degree programs in the biological sciences, fostering innovation and preparing students for leadership in research, education, medicine and industry. Nestled in a globally acclaimed and economically vibrant community, the school contributes to the university’s impact as Orange County’s largest employer and a significant economic contributor. Through its commitment to exploring life’s complexities, the Dunlop School embodies the UC Irvine legacy of innovation and societal impact. For more on the Charlie Dunlop School of Biological Sciences, visit https://www.bio.uci.edu/.