New shark species described

An Atlantic sixgill pup found off the coast of Belize. Credit: Ivy Baremore/MarAlliance 

Colleagues around the world are finding new species every day showing us how much we still have to learn about our planet's biodiversity. That being said, it is fairly rare that a new species of shark is described or resurrected based on additional evidence. 

Scientists of the Florida Institute of Technology confirmed after decades of uncertainty that sixgill sharks residing in the Atlantic Ocean are a different species than their counterparts in the Indian and Pacific oceans. With ancestors dating back over 250 million years, sixgill sharks are among the oldest creatures on Earth. Yet the fact that they reside at extreme ocean depths, sometimes hundreds of meters below the surface, has made them especially challenging to study.

Only by using two mitochondrial genes, COI and ND2, could the group confirm that bigeye sixgill sharks from the Atlantic Ocean (Belize, Gulf of Mexico, and Bahamas) diverged from those in the Pacific and Indian Oceans (Japan, La Reunion, and Madagascar). It also turns out that with up to 2m in length, Atlantic sixgill sharks are far smaller than their Indo-Pacific relatives, which can grow to 5m or longer. 

With their new classification, Atlantic sixgill sharks will now have a better chance at 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.