Water-Loving Animal Seems to 'Live Forever'
Scientists still puzzled by the hydra
By Neal Colgrass,  Newser Staff
Posted Feb 2, 2015 3:51 PM CST
Updated Feb 7, 2015 9:58 AM CST

(Newser) – A water-loving animal called the hydra may measure less than a half-inch, but still has something on us: It seems to live forever. Treehugger revisits this biological mystery, calling hydra "marvels of the animal world" that share "regenerative powers" with the multi-headed Hydra of Greek mythology. We know about hydra because—according to a video by two NPR reporters—a teacher discovered the plant-like creature in a pond 250 years ago and split it in half. Each half grew into two full-size hydra, so he split them in half, and each regenerated again. And so on. "It just wouldn't die," says the video. Could it be that hydra never perish? A scientist named Daniel Martinez tested this in the 1990s by keeping them in tiny water tanks to see if they would die in their natural habitat.

Four years later, he published a paper saying hydra don't die—or, to be specific, "Mortality patterns suggest lack of senescence in hydra." If four years seems hasty, it's based on the fact that in nature, "the sooner you have babies, the sooner you die," says the video. Flies, for example, have babies in a couple of weeks and die after a couple of months. Hydra give birth after a couple of days, but Martinez's hydra have now lived more than eight years, which is like an elephant living for 5,000 years. "Why the hydra?" asks video co-producer Robert Krulwich at Radiolab. "Why not (excuse me for asking) ... us?" Martinez theorizes that it's because the hydra's simple, embryonic cells stay young longer, and are replaced before they get old. (Want to know how long you've got? Poll your buddies.)