The Haenyeo girls who dive deep into the East China Sea to reap sea urchins and shellfish spend the most time underwater of any people ever studied — one to 5 hours a day, researchers report August 18 in Present Biology.
“It’s as shut as you get to finding out a mermaid,” says Chris McKnight, a marine mammal biologist on the College of St. Andrews in Scotland.
McKnight and colleagues labored with seven Haenyeo divers who reside on Jeju Island in South Korea. Over 1,786 dives, the ladies wore units that measured how lengthy they stayed underwater and the way deep they dove. The units additionally tracked oxygen ranges within the girls’s brains and muscle tissues.
The ladies dove repeatedly for 2 to 10 hours every day and spent a mean of 56 p.c of the time beneath the floor — extra underwater time than many aquatic mammals, together with beavers, polar bears and sea otters, the researchers say.
Chronicles of feminine divers on this a part of Asia date again 3,000 years. Researchers have studied the divers within the lab, however the crew needed to watch them in a real-life setting to place their talents in context with different water-dwelling mammals. Learning the Haenyeo girls’s physiological diversifications could make clear how the ancestors of whales and different marine mammals efficiently transitioned from a terrestrial to an aquatic surroundings, McKnight says.
The crew anticipated to see low oxygen ranges and gradual coronary heart charges within the Haenyeo, attribute of different mammals’ physiological dive response. As a substitute, it was the other: The ladies had elevated coronary heart charges and little or no oxygen discount of their mind or muscle tissues whereas diving, a shock that could be defined by the ladies’s frequent, shallow dives. The Haenyeo dives vary from three to fifteen toes deep, averaging 11 seconds in size with simply 9 seconds between dives to recuperate on the floor.
What makes the feats much more spectacular is the ladies’s common age: 70. “This speaks to an unimaginable well being span, which is actually thrilling, as a result of we might actually dig into what’s permitting that to be doable on this inhabitants,” says examine coauthor Melissa Ilardo, an evolutionary geneticist on the College of Utah in Salt Lake Metropolis. Ilardo led a lab-based examine that in contrast the Haenyeo girls with non-diving Koreans, and uncovered genetic variations within the divers from Jeju Island related to their blood stress in addition to their capability to resist chilly water, which can contribute to skillful diving, she and colleagues reported Might 27 in Cell Reviews.
McKnight says that the Haenyeo may have tailored to tolerate excessive ranges of carbon dioxide, which builds up within the physique after repeated breath holds. Elevated carbon dioxide ranges are “extremely uncomfortable” for many people, McKnight notes, inciting nervousness and panic. He hopes to watch the ladies’s CO2 ranges sooner or later.
The foraging practices of the Haenyeo are much like “a surface-oriented, shallow-diving marine mammal like a sea otter,” says marine biologist Ted Cheeseman, who heads Happywhale, a web based picture database of marine mammals, and was not affiliated with this examine. The diversifications that enable these girls to spend greater than half their time underwater “actually speaks to tradition driving evolution,” Cheeseman says.
