Ever wondered what a live shark’s reproductive organs look like on ultrasound? Well an adventurous team in the Galapagos Islands have recently found out. The team, led by Jonathan R. Green, managed to perform ultrasound scans of free swimming whales sharks of up to 45 feet in length in order to assess the ovaries and, in doing so, managed to see not only the ovaries but also the developing follicles within them.
“Almost nothing is known about the reproduction of these giant sharks. After I first saw these huge female whale sharks in the far north Galapagos, I realised that this was a great opportunity to learn more. We’ve been able to put together an experienced team to research sharks in this remote area, one of the world’s most isolated dive sites,” said Jonathan R. Green, the expedition leader and founder of the Galapagos Whale Shark Project.
As any sonographer worth their salt will know well, producing reliable images at depth is very difficult due to trade off with resolution. An issue which is particularly important given that whale skin can be up to 20cm thick. So how did the team of scientists manage to capture these images? The first challenge was to have an underwater system capable of being submerged in water. Then came the fact that the ultrasound equipment was not exactly portable at 17kg or streamlined. And to make things even more difficult, while carrying all this equipment the team needed to be as agile and as fast as the moving sharks. They also needed to scan the entire length of the shark’s belly – which is no easy feat given their size and speed.
“We used some interesting technology anyway, but working with the Okinawa team was something else”, commented Dr Pierce. “I felt cool by association. We saw dive groups a couple of times at the site, and I can only imagine what they thought – why is that guy diving with a briefcase? And a jetpack?”
Dr Matsumoto added that the initial results were promising: “We confirmed the presence of follicles in the ovaries but none of the images captured embryos or egg capsules inside the uterus. These adult female sharks we saw at Darwin Island might be on their way to mate further offshore. I am confident that we can judge the sexual maturity, and probably also determine the pregnancy of whale sharks in the field, using the underwater ultrasound”.