Researchers at Florida Atlantic University (FAU) have used high-resolution imaging techniques to examine the skin of bonnethead sharks, a small relative of hammerhead sharks, in order to better understand how the microscopic structures known as dermal denticles change as the animals grow.
Dermal denticles are tiny, tooth-like structures made of the same material as teeth. They help sharks move efficiently through water and protect their skin, especially during mating. While scientists have known about these structures for some time, questions remained about how their shape and structure vary across different parts of a shark’s body and between males and females.
To address these questions, FAU researchers used advanced scanning electron microscopy to capture detailed images of bonnethead shark skin from 24 individuals at various life stages. The imaging focused on small features such as denticle shape, size, and ridge patterns—details not visible with standard microscopes.
The findings, published in Integrative and Comparative Biology, indicate that as bonnethead sharks mature, the morphology of their skin denticles changes significantly. Younger sharks were found to have fewer ridges on their denticles, less overlap between them, and smaller ridge angles compared to older sharks. However, the overall length of the denticles did not change with age. These changes are believed to improve swimming efficiency and skin protection as sharks grow.
“Shark skin is far more dynamic than people realize,” said Marianne E. Porter, Ph.D., senior author and 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.”
Previous research suggested female sharks might have thicker skin and higher denticle density to protect against male bites during mating. However, this study found only minimal differences between males and females in bonnethead sharks. The only notable difference was that males had slightly larger ridge angles on their denticles. There were no significant differences across the dorsal, medial, and ventral parts of the abdominal region.
“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 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.”
Patterns observed in this study were similar to those found in other shark species such as Portuguese dogfish, which show different denticle shapes at various developmental stages. Past research has also shown juveniles tend to have smaller denticles than adults—a trend also seen 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 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 at FAU offers students access to high-tech equipment for research projects across various fields such as cancer treatment, vaccine development, and prosthetics creation. The lab is equipped with advanced imaging tools and is available to researchers at all levels within FAU.
Madeleine E. Hagood, a Ph.D. student of integrative biology at FAU, is also a co-author of the study. 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.
