Researchers at the Florida Institute of Technology have now confirmed that the Atlantic sixgill shark is a separate species from those residing in the Indian and Pacific ocean.
The Atlantic sixgill shark is one of the oldest species on the Earth, with ancestors dating back long before the existence of dinosaurs – over 250 million years ago. However, because these sharks live at incredible depths, it has been difficult to study them in depth. For this reason, it was not certain for decades whether the Atlantic sixgill shark was actually part of the same species we found in the Indian and Pacific Oceans.
Toby Daly-Engel, an assistant professor of biological sciences at Florida Institute of Technology, led the team in looking through 1310 base pairs of two mitochondrial genes. She worked in collaboration with colleagues from MarAlliance in Belize, the National Marine Fisheries Service, The Southeast Fisheries Science Center in Panama City, and the University Coastal and Marine Laboratory in Teresa, Florida. This multidisciplinary team determined that there are enough genetic differences to establish the Atlantic sixgill shark as its own unique species – renamed as hexanchus vitulus.
“We showed that the sixgills in the Atlantic are actually very different from the ones in the Indian and Pacific Oceans on a molecular level, to the point where it is obvious that they’re a different species even though they look very similar to the naked eye,” Daly-Engel said.
At only around 6 feet in length, the Atlantic sixgill shark is less than half the size of their cousins in the Indian and Pacific Ocean – organisms that can grow up to 15 feet or longer. The fact that the shark has six gills is also rather unique (hence the namesake) due to the fact that the majority of sharks only have five gill slits.
While identifying the Atlantic sixgill shark as its own species is important for academia in and of itself, Daly-Engel also believes that it has the potential to help the species out in terms of long-term survival.
“Because we now know there are two unique species, we have a sense of the overall variation in populations of sixgills. We understand that if we overfish one of them, they will not replenish from elsewhere in the world,” she said.
At the end of the day, we honestly don’t know very much about the Atlantic sixgill shark or its brethren, due to the fact that they’re extremely difficult to locate and study. Understanding that these sharks are disparate species calls attention the fact that the population of these different sharks may actually be much smaller than initially anticipated. With the numbers now spread over at least two species, it’s possible that the population isn’t as healthy as we had thought.
Daly-Engel also stated this is important for the study of the diversity of sharks in general, given that our knowledge in this field is particularly lacking.
“Particularly diversity in the deep ocean…which we don’t know much about.”
More research in the future will help us learn more about these fascinating deep ocean dwellers and help us work to better protect them moving forward.