(Press-News.org) Have you ever wondered what makes shark skin so tough and sleek? It’s dermal denticles – tiny, tooth-like structures that cover a shark’s skin. Made of the same material as teeth and shaped like small scales with grooves, these microscopic armor plates aren’t just for show. Dermal denticles serve important roles in helping sharks glide effortlessly, and protect their skin, especially during mating.
Although much is known, researchers still lack a full understanding of how dermal denticle shape changes across different parts of the shark’s body as it grows and if there are differences between males and females.
To solve this mystery, researchers from Florida Atlantic University turned to high-resolution imaging to examine bonnethead sharks (Sphyrna tiburo) – the pint-sized cousins of hammerhead sharks. Using advanced scanning electron microscopy, they were able to capture detailed images of the sharks’ skin, focusing on minute features like denticle shape, size and ridge patterns – details far too small to be seen with standard microscopes.
The team studied skin samples from 24 bonnethead sharks across various life stages. These sharks were an ideal subject, as their skin denticles undergo noticeable changes as they grow and show distinct features between males and females, especially in areas linked to mating.
Findings, published in the journal Integrative and Comparative Biology, provide an ultra-magnified peek into the hidden world of shark skin, revealing how evolution fine-tunes this natural armor for survival and reproduction.
Results of the study showed that denticle morphology changes significantly as bonnethead sharks mature, supporting the idea that these changes improve swimming efficiency and skin protection. Younger sharks had fewer ridges on the denticles, less overlap between them, and smaller ridge angles compared to older sharks. However, the overall length of the denticles stayed about the same at all stages. These changes likely help sharks swim better and protect their skin as they mature.
“Shark skin is far more dynamic than people realize,” said Marianne E. Porter, Ph.D., senior author and an associate professor of biological sciences in FAU’s Charles E. Schmidt College of Science. “Our study shows that as bonnethead sharks grow, their skin doesn’t just get bigger – it transforms in ways that improve swimming performance and provide greater protection. These changes help reduce drag in the water and strengthen the skin against physical challenges like predators or mating-related injuries. It’s a remarkable example of how nature fine-tunes biological structures to meet the changing demands of an animal’s life.”
Although previous studies found that female sharks often have thicker, tougher skin with higher denticle density – possibly to protect against male bites during mating – this study found minimal differences between the sexes. The only denticle trait that showed sexual dimorphism was ridge angle, which was slightly larger in males. There were also no significant differences in denticle features across the dorsal, medial and ventral parts of the abdominal region studied.
“This research is relevant because gaining an understanding of the developmental aspects of a shark’s dermal denticles can provide extraordinary insights into their evolutionary role in facilitating survival locomotion and reproductive materials,” said Hannah Epstein, corresponding author, a recent graduate of FAU High School and a current student in FAU’s Harriet L. Wilkes Honors College. “We can also apply these quantifications of shark skin to other fields, such as bioengineering, to specifically design materials that can help someone swim faster, just as denticles help a shark swim faster.”
The patterns observed in this study mirrors findings in other species, such as Portuguese dogfish sharks, which have 11 different denticle shapes that appear at different developmental stages. Past research has also shown that juveniles tend to have smaller denticles than adults, a trend that held true for bonnethead sharks in this study.
“The advanced imaging and analysis tools we have at the Marcus Research and Innovation Center were essential for this research,” said Tricia Meredith, Ph.D., co-author, director of research for Florida Atlantic Laboratory Schools, and an assistant research professor in FAU’s College of Education. “Using scanning electron microscopy and precise morphometric software allowed us to see and measure the tiny details of shark denticles like never before. This technology opens up new possibilities to understand how these structures function and evolve, giving us a clearer picture of shark biology and biomechanics.”
The Berlin Family Bioimaging Lab is a one-of-a-kind research laboratory that provides students access to high-tech equipment to work on complex research projects, including cancer treatment research, vaccine development, and prosthetic creation, among others. Students like Epstein can research some of the world’s most challenging problems at an early age and can share that research and publish it in peer-reviewed journals. The lab includes a micro computed tomography scanner; scanning electron microscope; histology suite; inverted compound microscope; and stereoscope and is available to researchers of all levels at FAU.
Study co-author is Madeleine E. Hagood, a Ph.D. student of integrative biology at FAU.
The research was supported by a National Science Foundation CAREER Award grant, awarded to Porter, and an FAU Office of Undergraduate Research and Inquiry grant awarded to Epstein.
- FAU -
About Florida Atlantic University:
Florida Atlantic University serves more than 32,000 undergraduate and graduate students across six campuses along Florida’s Southeast coast. Recognized as one of only 21 institutions nationwide with dual designations from the Carnegie Classification - “R1: Very High Research Spending and Doctorate Production” and “Opportunity College and University” - FAU stands at the intersection of academic excellence and social mobility. Ranked among the Top 100 Public Universities by U.S. News & World Report, FAU is also nationally recognized as a Top 25 Best-In-Class College and cited by Washington Monthly as “one of the country’s most effective engines of upward mobility.” As a university of first choice for students across Florida and the nation, FAU welcomed its most academically competitive incoming class in university history in Fall 2025. To learn more, visit www.fau.edu.
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