On June 29, 2019, a group of researchers submerged off the coast of Eleuthera, in the Bahamas. They were aboard the Nadir, a submersible that allowed them to go down to a depth of one thousand meters in the waters of the Gulf of Mexico. Down there, where the sunlight doesn’t reach, they had an extraordinary encounter: they spotted a comb shark, a species 200 million years old.
“It was like seeing a T. rex in the water”
So said Gavin Naylor , director of the Shark Research Program at the Florida Museum of Natural History. Naylor was leading the expedition, accompanied by Dean Grubbs of the University of Florida, Brendan Talwar and Edd Brooks, both of the Cape Eleuthera Institute. The four formed the team of scientists who descended under the command of Lee Frey, the pilot of the Nadir, a submarine launched from Alucia, a ship of the OceanX ocean exploration initiative. The goal was to find specimens of a species of shark that is still with us after hundreds of millions of years. In fact, the comb shark is a prehistoric species that existed twenty million years before the age of the dinosaurs.
“This lineage has been around 100 times longer than Homo erectus, and these sharks haven’t changed that much.”
a prehistoric shark
The comb shark is as Hexanchus griseus is known. It also receives names such as gray boot or sixgill shark. And it is precisely that it belongs to the Hexanchidae family, sharks with six and seven pairs of gills considered the most primitive among sharks. They are also the largest of the family, with specimens that can exceed six meters in length.
In addition to the more pair of gills compared to other sharks, Hexanchus griseus is characterized by having a flattened snout. It has a terrifying mouth (in addition to the trauma that Steven Spielberg and his movie “Jaws” has left us forever) with a row of teeth in the upper jaw and six rows of comb-shaped teeth in the lower jaw .
They have huge, elliptical, fluorescent, greenish eyes. With its gray hue and darker fins, it blends perfectly into the darkness of the great tropical and temperate depths it inhabits.
These sharks survived the Permian-Triassic mass extinction. Thanks to the fact that the dark and deep waters that they inhabit are hardly affected by drastic climatic changes , this species has been able to adapt to its environment over hundreds of millions of years and avoid the extinctions that wiped out a very high percentage of the species that have lived on our planet.
an unknown species
Despite the interest in sharks, this prehistoric species has not received much scientific attention . Undoubtedly, one of the reasons is the difficulty involved in spotting them. It is possible that the human being steps on the surface of Mars before the deeper soil under the waters of our own planet.
The comb shark lives at a depth of between 200 and 1,000 meters , although Dean Grubbs has records of specimens swimming at 1,500 meters. That is why this expedition that sighted several specimens in 2019 had so many setbacks. You need a submarine, almost 1,000 kilos of bait, special harpoons and the weather with calm seas. On June 29, after several failed attempts, the investigation team tried one last time when the night had already caught them in full swing. Luck favors the bold.
How do you study a shark that lives so deep?
They spotted a male at a depth of 500 meters. The team had two chances to shoot a tag to tag the shark. Naylor, who had never been in a submarine, hit his shot.
This tag will record data on the depth in which the shark moves, the light and temperature to which it is exposed and all this over three months. When the time comes, the tag comes off and rises until it floats on the surface of the sea, transmitting the stored data via satellite . State-of-the-art technology to learn a little more about the habits and way of life of one of the greatest survivors in the history of life on Earth.
The researchers investigated
The Nadir was going down in search of sharks when a 5-meter female approached the submarine. He made a careful examination of the strange intruder that had appeared in his habitat. Naylor said it was the most magical experience he had ever had. He was in the dark, stuck in an underwater balloon, in a place that seemed like another world. His hair stood on end when he was observed by a shark that has been hunting in the deep sea for 200 million years.
“He was studying us. It was wonderful for me to see a shark being curious.
We would be arrogant if we thought that we are the only ones doing the evaluation.”
We are lucky to have the images recorded during the dive, available on the OceanX channel.
Reference:
van Hoose, N. 2019. Florida scientists tag deep-sea shark from submersible. floridamuseum.ufl.edu.
