The fish died after living in the aquarium for many years what feature of life is that illustrated?

The feature of life illustrated by the fish dying after living in an aquarium for many years is death.

Here's why:

* Death is a fundamental characteristic of all living things. It is the cessation of all biological functions that sustain a living organism.

* All living things eventually die. This is part of the natural cycle of life.

* The fish's death, after a long life in the aquarium, highlights the inevitability of death.

While the fish's death could have been caused by various factors (old age, disease, environmental changes), the underlying principle is that death is a defining characteristic of life itself.