Turtles live a ridiculously long time. The oldest known turtle — a Seychelles giant tortoise named Jonathan is 186 years old and still kicking! Galapagos tortoises have produce healthy, viable young past their 80th birthday. And even smaller species can live for half a century, as long as they aren’t eaten or run over first.
Scientist aren’t 100% sure how these animals live so long but a lot of it seems to build down to preventing wear and tear to the body. In most species, including ours, the odds of dying go up as you get older. That’s because our bodies just kind of deteriorate over time.
Like many machine, parts slowly wear down, and that eventually leads to some kind of catastrophic failure. But that’s now always the case in turtle, in some, being old means they are less likely to croak. And they can even still have healthy offspring.
This ability to stay alive and have healthy babies despite being old is called negligible senescence. And though some of the details are still unclear, it seems turtles pull this off thanks to a remarkable tolerance for oxidative stress. That’s the harm to cells that happens due to react oxygen species or ROS: a family of oxygen-containing compounds that really, really like interacting with other molecules.
The accumulation of this damage, especially to neurons and immune cells, is thought to drive raging. But reactive oxygen species aren’t evil, they are produced all the time, like in the calorie burning process that turns food into cellular fuel.
So the key is not getting rid of Ross, but keeping them under control. One of the ways turtles do that is by producing less of them. They have a slow metabolism, which means they need fewer calories than other animals of similar size. It also helps that they are poikilothermic: their bodies can function at a wide range of temperatures. So they are not as stressed by cold or hot temperature as we are — and less stress means less ROS.
They also have ways to manage the ROS they do produce. Since these compounds can damage telomeres- the protective caps of DNA that shorten every time a cell divides, turtles produce lots of the enzymes tellers, which helps prevent that shortening. And that helps keep their cells healthier longer lessening their odds of developing cancer or other diseases.
They also make lots of strong antioxidants and other proteins that fight cellular damage. While these traits might seem like the perfect adaptations for a long and healthy life, biologist think they arose for another reasons: surviving without oxygen.
Many turtles, including those cut red-eared sliders you might have seen in pet stores, can go weeks without breathing air, a handy trick if you want to spend the winter in an icy pond. They have special ways of keeping important tissue alive during that time, like shutting down oxygen hungry neural circuits. But they also have to deal with the burst of ROS production that happens when they finally come up for air and oxygen levels rapidly rise, which is there those antioxidants and cell healing proteins came into play.
So their longevity might be a happy side effect, one that some researchers are hoping to translate into longer, perhaps even definitive lives for people. But we can’t really replicate all of their tricks like becoming poikilothermic.