Tom Wellenmann via Flickr
These creepy crawlers, also known as planarian worms, are famous for their regeneration abilities, where a worm cut across or lengthwise can form two separate worms. This apparently limitless regeneration also applies to aging and damaged tissue, allowing the worms to cheat death indefinitely, according to a study at the University of Nottingham.
Though not technically immortal animals, the bowhead whale is the oldest living mammal. According to Popular Science, several species of whales have been known to live for more than 70 years, though in the 1990s scientists discovered scars on the massive animals that had been made by weapons from the 1800s. The oldest known bowhead lived to be 211 years old. Whales are also very smart. This particular one even thanked the scientists who rescued him from a fishing net.
Deinococcus radiodurans, a poly-extremophilic bacterium, isn’t only radiation-resistant. These immortal animals can also die and come back to life thanks to their incredible DNA repair response. According to Ira S. Pastor, CEO of Bioquark Inc., “[They] can survive cold, dehydration, vacuum, and acid, and [have] been listed as the world’s toughest bacterium.” The Guinness Book of Records even says they “can resist 1.5 million rads of gamma radiation, about 3,000 times the amount that would kill a human!”