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Caitlin Bailey, a senior majoring in marine science at the University of Delaware, holds the jaw of a sand tiger shark. This shark species, which is federally protected in U.S. Atlantic waters, has an unusual reproductive strategy. The first shark to hatch from its egg case (while in its mother’s uterus) seeks out and devours its smaller, less fortunate siblings. Bailey is examining how and why this shark’s teeth change at various life stages.
Caitlin Bailey, a senior majoring in marine science at the University of Delaware, holds the jaw of a sand tiger shark. This shark species, which is federally protected in U.S. Atlantic waters, has an unusual reproductive strategy. The first shark to hatch from its egg case (while in its mother’s uterus) seeks out and devours its smaller, less fortunate siblings. Bailey is examining how and why this shark’s teeth change at various life stages.

A sharper look at shark teeth

Photos by Evan Krape and courtesy of Caitlin Bailey | Photo illustration by Jeffrey C. Chase

UD undergraduate student Caitlin Bailey examines sand tiger shark teeth

Editor’s note: Every year, hundreds of undergraduates at the University of Delaware pursue research under the guidance of a faculty mentor. Such experiences provided by UD — a nationally recognized research university — can be life-changing, introducing young scholars to a new field, perhaps even the path to a future career, as they uncover new knowledge. These spotlights offer a glimpse into their world. 

With rows of long, razor-sharp teeth jutting out from a mouth that never closes, sand tiger sharks inspire awe at marine aquariums worldwide. Despite their fearsome appearance, these sharks are not aggressive to humans. Rather, humans are the sand tiger shark’s top predator. It is federally protected in U.S. Atlantic waters and is listed as critically endangered in some parts of its global range.

At the University of Delaware, Caitlin Bailey, a senior majoring in marine science from Chatham, New Jersey, is taking a closer look at this shark’s teeth. Her adviser is Jennifer Wyffels, a researcher at Ripley’s Aquariums and UD’s Center for Bioinformatics and Computational Biology, who received project support from Ripley’s Aquariums. 

What are you studying and why?

Bailey: Sand tiger sharks are remarkable to me because they are the only documented species of shark that uses in utero sibling cannibalism (adelphophagy) as a reproductive strategy. The first shark to hatch from its egg case (while in the uterus) seeks out and devours its smaller and less fortunate siblings. Gestation lasts approximately 10 months and the surviving embryo grows to nearly a meter in length before birth. Once I learned about this unique and extreme reproductive mode, I was enthralled and wanted to research the species more.

Sand tiger shark teeth at various life stages. One of the more obvious changes observed is in the lateral cusplets, which become more prominent in larger sharks.
Sand tiger shark teeth at various life stages. One of the more obvious changes observed is in the lateral cusplets, which become more prominent in larger sharks.

At different life stages, sand tiger shark teeth change in morphology. The shifting tooth shape might reflect changes in their diet. I am using microtomography (micro-CT) to image the teeth in 3D and collect measurements to compare tooth morphology between adult and immature sharks.  One of the more obvious changes observed is in the lateral cusplets, which become more prominent in larger sharks. I am intrigued by these changes and the reasons for them, as well as comparing the anatomy of the teeth between life stages to understand sand tiger sharks further. 

How did you feel when you first held one of the shark’s teeth?

Bailey: I was honestly nervous since breaking or damaging any of the teeth would be a major setback for the project. I still maintain caution when handling the teeth, but now I am more inspired when I hold them, and I realize they are not very fragile. It makes me excited to get to work and understand more about sand tiger sharks as a species.

Some of the teeth Caitlin Bailey has analyzed are from a sand tiger shark named “Rip” born at Ripley’s Aquariums two years ago, as well as from adult sharks there. Ripley’s Aquariums provided funding for the research.
Some of the teeth Caitlin Bailey has analyzed are from a sand tiger shark named “Rip” born at Ripley’s Aquariums two years ago, as well as from adult sharks there. Ripley’s Aquariums provided funding for the research.

Why does research like this matter?

Bailey: Research like this fills in gaps about the basic biology and physiology of the species. It helps with understanding the ecological niche of sand tiger sharks in various life stages. Furthermore, this research allows for a more extensive understanding of tiger shark gestation and growth.

What’s the coolest thing about being involved in this project? Any surprising or especially memorable experiences?

Bailey: The coolest part of this project is creating the 3D reconstructions and being able to compare and contrast the various textures and shapes present in the teeth at each life stage.

A 3D reconstruction of a sand tiger shark tooth that Caitlin Bailey is working on, with support from UD’s Center for Biological and Brain Imaging.

The most memorable experience was CT-scanning the teeth with Dr. Mary Boggs at the Center for Biological and Brain Imaging on campus. The CT scanner makes virtual sections through the sample. These sections are then put back together or reconstructed with the help of software. Once reconstructed, measurements can be collected digitally using internal and external features of the teeth. The process was so intriguing, and the results are vital to understanding more about the various functions of these teeth throughout the sand tiger’s life. 

Is there anything you've discovered about yourself and your career goals as you've worked on the project?

Bailey: I have really enjoyed setting my own pace and being able to work through roadblocks myself. I have enjoyed working with many different researchers and, as a result, would like to work with a wide array of perspectives and expertise in my future career.

What career are you aiming for?

Bailey: I would like to work with aquatic species at an aquarium or zoo as either a veterinarian or aquarist. This would require collaboration with various researchers, caretakers and aquatic veterinarians. 

What do you enjoy doing in your spare time?

Bailey: I enjoy being on the beach, reading and doing technical theater with the Harrington Theater Arts Company on campus.

UD undergraduate student Caitlin Bailey (left) examines the jaw of a sand tiger shark with her research project adviser, Jennifer Wyffels.
UD undergraduate student Caitlin Bailey (left) examines the jaw of a sand tiger shark with her research project adviser, Jennifer Wyffels.

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