By: Jasmine Nyce, M.S. Student & Station Administrator
As scientists, we use many tools and techniques to answer research questions. Based on the nature of the questions, we may need to collect blood samples, tissue samples, morphological measurements, or even an ultrasound to look for trends and make conclusions about the study species. As an undergraduate student, I had opportunities to observe graduate students and principal investigators use ultrasound machines on various elasmobranch species. When I came to the Shark Lab as a volunteer, I was pleased to find out that the lab also had an ultrasound machine and used it for a multitude of previous projects. I was always awed by the information you could obtain from a single scan. The technique was something I had always wanted to learn myself, and I had to chance to do it recently.
At the end of 2022, I joined a group of scientists in a workshop by Dr. Natalie Mylniczenko, who gave us a crash course on ultrasounds, specifically on elasmobranchs. The day started with a lecture introducing us to the terminology and techniques behind ultrasound. In simple terms, ultrasound is sound waves released from a transducer toward a target tissue, which then bounces back to the computer, and an image is reconstructed. This reconstructed image allows the technician to determine various things, including, but not limited to, an individual's body condition and reproductive status.
We dove deeper into the art of scans and learned that the black on the image typically indicates water or fluid, while white would indicate hard tissue, such as bone. The grey tones can show the tissue's or object's density. On each ultrasound machine, you can adjust the depth and gain (similar to the contrast of a photograph), allowing you to create clearer images depending on the species you are working with and the conditions during the scan. The transducer (or probe) can also be held in different orientations to create additional images. The probe provides a cross-section of the tissue below it in a fanning shape. It can be held in a transverse or sagittal orientation, giving the technician different angles and images of the target tissue. Dr. Natalie showed us many examples from her experiences and harped that understanding species' anatomy is of utmost importance when doing ultrasounds, especially considering the diversity of elasmobranch anatomy and reproductive modes.
We then moved on to practice, as there is no better way to learn than hands-on experiences with these techniques. We used our ultrasound machines on a Jell-O mold that Dr. Natalie had created for us. Inside the dark-colored Jell-O were objects we all would know and could find in households. We were able to practice changing the depth, gain, and probe orientation to figure out what objects were inside. When we found something below our probe in the Jell-O, we were urged to slow down and try different scans over that object. Slowly but surely, we started to figure out some objects: hard-boiled eggs, pasta, spam, corn, and other food items. We all knew what these objects looked like, but the ultrasound images were presented in a way that we didn’t recognize and comprehend what the everyday object was. We kept working, and by the end of the first practice, we could easily comprehend what was being scanned in the Jell-O by the ultrasound.
After a quick lunch break, we performed some ultrasound scans on cadavers of elasmobranchs (all under permits from colleagues). We were able to get more comfortable with scanning the common anatomy of elasmobranchs, such as the spiral valve and intestinal tract. This time also allowed us to pick the brains of Dr. Natalie and her veterinary technicians on utilizing ultrasound technology in our research. For my research, I was looking to confirm pregnancy. To do this, I would need to scan the body over the reproductive organs to look for pups. In the case of the study species for my thesis, bull sharks (Carcharhinus leucas), we were looking for what was described to me as small tuna steaks. If you think about it, you would be able to see the small vertebrate in the center, with muscle surrounding it and the skin layer on the outside. The trick was learning the anatomy of bull sharks to ensure I didn’t mistake the pups for other organs in the mom. Other elasmobranch species may have a different mode of reproduction; therefore, the scans to determine pregnancy may look different than those for bull sharks. For example, in tiger sharks (Galeocerdo cuvier), you can often see a pup's whole head later in development due to how pups are laid down in the uterus. The vast differences in elasmobranch reproduction and anatomy make ultrasound scanning for this group of animals a bit difficult but incredibly interesting!
By the end of the day, we had lots of hands-on experience using different ultrasound machines and walked out feeling more comfortable with the technique. Becoming an ultrasonographer takes more than a day, but the experience was the perfect kick-off. This technology allows us to ask more questions about an animal’s health and reproductive status, which, in turn, creates a better understanding of the movements and behavior of animals. I have been fortunate enough to be able to do scans on various elasmobranchs, including some for my thesis. Just like many other techniques and skills in the field of science, practice makes progress. A special thank you to Dr. Natalie for providing an incredible opportunity to learn about ultrasound technology and get comfortable using the technique in fieldwork - funny to think back on it now and how it all started with an ultrasound of Jell-O.