Scientists recently confirmed the Atlantic sixgill shark as a new and distinct species of shark, following extensive genetic analysis that separated them from their relatives in the Indian and Pacific Oceans.
Citing a study published in the journal Marine Biodiversity, Science Daily wrote the species was confirmed “after decades of uncertainty,” as researchers weren’t quite sure what to make of the Atlantic sixgills, which share many similarities with their relatives from the Indo-Pacific. The Atlantic species, however, is noticeably smaller, with a maximum length of 6 feet, as compared to the Indo-Pacific sixgills, which can grow to lengths of more than 15 feet. Atlantic sixgill sharks also have “saw-like” rows of lower teeth, slightly setting them apart from their relatives.
Sixgill sharks, in general, get their name from the fact that they have six gills, as opposed to most other shark species, which have five. They are among our planet’s oldest animals, as their ancestry dates more than 250 million years ago, or a few tens of millions of years prior to the emergence of dinosaurs. According to Science Daily, the creatures have long been difficult to study, as they typically can only be found in deep waters, sometimes as far down as a few thousands of feet below surface level.
In the new study led by Florida Institute of Technology assistant professor of biological sciences Toby Daly-Engel, researchers conducted an in-depth analysis of the Atlantic sixgill shark, taking over 1,300 base pairs of two mitochondrial genes to determine whether it is a distinct species or not. Ultimately, it was found that there were enough differences between the Atlantic sixgill’s genes and those of sixgills found in the Indian and Pacific oceans to consider it a new species, which was given the scientific name 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 in a statement.
Further commenting on her team’s findings, Daly-Engel added that the study offers more clarity on the diversity of sixgill shark populations and deep ocean creatures in general. She said that the discovery of a new species has serious implications with regard to overfishing, and how it could jeopardize these populations.
“We understand that if we overfish one of them, they will not replenish from elsewhere in the world.”
According to Sputnik News, the new discovery made the Atlantic sixgill shark the third species of its kind to be confirmed as distinct, following the bluntnose sixgill and the bigeyed sixgill.