A 400-year-old shark just whispered its DNA secrets
The News
Scientists at the University of Tokyo, led by Shigeharu Kinoshita, just mapped 96.7% of the genome of a Greenland shark — the very first time anyone has done that. Greenland sharks are remarkable: they can live for around 400 years , don't become adults until they're 150, grow to 13–16 feet long, and cruise in the cold dark waters of the North Atlantic and Arctic down to 1.65 miles deep. By reading their DNA, scientists hope to learn how these giants avoid cancer and live so astonishingly long. The study was published May 19 in PNAS .
Professor Pip pulled his magnifying glass from his coat pocket and pressed it against the glowing blue glass of his big lab tank. Inside, a long, slow, pale-grey shadow drifted by — the size of a small canoe.
"Children," Pip whispered, "meet a Greenland shark. The longest-lived backboned animal on the entire planet."
Mia pressed her cheek to the glass. "How old is it?"
"Some are four hundred years old," Pip said. His spectacles slipped down his nose and he didn't even notice.
Leo's mouth fell open. "FOUR HUNDRED?!"
"This shark," Pip said, tail swishing in slow ocean rhythm, "could have been born before electricity, before cars, before airplanes. It is still swimming. And it doesn't even become a grown-up until it's 150."
"It's a teenager longer than my whole grandma's life!" Mia gasped.
Pip clapped his paws. "Precisely!"
He pulled his chemistry flask of bright green liquid from a pocket and set it gently on the table. "Scientists in Japan just did something wonderful. Every animal carries an instruction book in every one of its cells. We call that book the genome. It tells the cell what to build, what to fix, what to throw away."
He tapped the flask. "These researchers read almost the entire Greenland shark instruction book — page 1 to page 96.7 out of 100. They want to know: what does it say? What chapters does this shark have that we don't? Why does it almost never get cancer? Why doesn't it seem to grow tired?"
Leo squinted at the slow grey shape. "Maybe it doesn't get tired because it's so slow. My grandpa says he saves energy by sitting down."
"Exactly right!" laughed Pip, eyes shining. "Greenland sharks live where it's cold and dark, more than a mile deep — pressure, ink-black ocean, freezing water. Going slowly is one of their secrets. So is having a body that knows how to fix its own damage, again and again, for centuries."
Pip looked into the tank. "Imagine. Out in the Arctic, right now, sharks older than this building are paddling silently in the dark. Reading their DNA might teach us how to live longer, healthier lives."
He handed Mia and Leo each a little notebook. "Now you try. Write down three questions you'd ask this shark — if it could answer."
Spark a Conversation
- If you could ask a 400-year-old shark one question, what would it be?
- What do you think would be hard about being alive for 400 years? What would be wonderful?
- Why do you think living down in the deep, cold ocean might help an animal live so long?