Encomium Moriae

There are many examples of species for whose organisms scientists have not detected an increase in mortality rate after maturity. In other words, they are equally likely to die at any given age after maturity; or, alternatively, it could be that the mean lifespan of the organisms is so long—multiple millennia—that researchers haven't yet had the chance to live up to the time when a measure of the species' longevity can be made. See also Late-life mortality deceleration.

However, there are also organisms that exhibit negative senescence, whereby mortality chronologically decreases as the organism ages, for all or part of the life cycle, in disagreement with the Gompertz–Makeham law of mortality.^[2]

Furthermore, there are even more peculiar examples, those of species that have been observed to regress to a larval state and regrow into adults multiple times; exempli gratia, T.nutricula.^[3]