I’m always on the lookout for stories about evolution of negligible senescence — situations in which organisms from mortal/aging clades evolve out from under the necessity of growing older. This generally happens because of unusual life histories: increasing fecundity with age is one way to trick natural selection into helping you out, as is finding a niche that forces young and old into a waiting game.

The selection pressure that drives such evolutionary events tells us very little about the molecular and cellular mechanisms by which the effective immortality is actually achieved, but it does point us in the direction of the right organisms to study.

Here’s a new one on me*: Turritopsis nutricula, a hydrozoan that is effectively able to reverse the aging process and revert to a juvenile state after becoming sexually mature. I learned about it in this breathless Telegraph piece (“‘Immortal’ jellyfish swarming across the world”), which appears to have been derived from the more sedate piece in the Times (“Turritopsis nutricula: the world’s only ‘immortal’ creature”) by the removal of complex sentences and the insertions of dumb lines like

Marine biologists say the jellyfish numbers are rocketing because they need not die.

Really? Not surprising that they weren’t able to get an attributed quote on that one. Evolved negligible senescence does not mean biological immortality, or the ability to grow arbitrarily well in any environment. Turritopsis is spreading because it’s an effective invasive species, not because it’s “immortal”.

Still, we’d like to know how it does its little trick. I’m not, however, holding my breath hoping it will generalize to vertebrates.

*All the more embarrassing for me since one of Ouroboros’ regular contributors uses the genus name as her handle; you’d think I would have looked it up.