New answers tagged senescence
Yes, at least some fishes have intrinsic lifespans and deaths that are related to their own life-history and not to external forces such as predation or disease. Fishes show three types of senescence. Lampreys, eels and pacific salmon exhibit rapid senescence and sudden death at first spawning. The guppy, red panchax, medaka, platyfish, Indian murrel ...
Fish do not die from old age, nor do any other animals. Rather, the older the animal gets the weaker it becomes which means that it is an easier target for predators or can easily succumb to disease.
In addition to the above answers, the answer to your question also depends on your definition of immortality. There are a number of clonal organisms (the most famous of which is probably Pando, a quaking aspen https://en.wikipedia.org/wiki/Pando_%28tree%29 ) where there is a large area, sometimes multiple square miles, where individual shoots are sent above ...
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