> Which animal has a subspecies that's considered to be biologically immortal?And the answer: jellyfish. Also known as the immortal jellyfish, the Turritopsis dohrnii is a species ofsmall jellyfish found in warm waters around the world. When exposed to stress orillness, it can revert back to an earlier stage, and grow through its lifestages again, theoretically continuing this cycle for eternity.This tiny jellyfish is unequivocally more prepared than many of its jellyrelatives. Where every other species of jellyfish awaits post-reproduction death(if they have not otherwise been eaten by some other organism), the Turritopsisdohrnii becomes effectively immortal because of its ability to transform fromthe medusa stage (fully formed jellyfish) back to the polyp stage (nearequivalent to a tadpole), thereby escaping death. Though jellyfish populate nearly every saltwater congregation (and even somefreshwater) on this planet, their life cycles are complex and poorly understood.These creatures are ancient, dating back millions of years before the dinosaurs.Interestingly, their physiology is remarkably similar to their prehistoricancestors', but the wide variation of form and unpredictable survival patternsmake it difficult to study these jellies of the sea. Jellies can vary greatly in size. From those measuring in at just one cubiccentimeter across, to those with up to 7 feet in diameter (plus 120 feet inlength!), it's no understatement to say that jellyfish come in all shapes andsizes. Ironically, the smaller the jellies are, the more venomous they can be.The smallest jellyfish known to man, the Irukandji jellyfish, packs a punch 100times[https://books.google.com/books?id=v3uDCwAAQBAJ&pg=PA176&lpg=PA176&dq=100+times+as+potent+as+that+of+a+cobra+and+1,000+times+as+strong+as+a+tarantula&hl=en#v=onepage&q=100%20times%20as%20potent%20as%20that%20of%20a%20cobra%20and%201%2C000%20times%20as%20strong%20as%20a%20tarantula&f=false] as potent as that of a cobra and 1,000 times stronger than a tarantula's. And,as if that wasn't enough, check out this photo of the lion's mane jellyfish (thebiggest jelly documented to date):Though they have no brain, heart or eyes, and are composed mainly of water,these creatures of the sea are some of the most magnificent and fascinatingcreatures on the planet. Check out this Nat Geo video for more:
