The animals that dies after childbirth include the octopus, the squid, salmon and the common mayfly.
And for the most part, the males die soon after fertilizing the female's eggs and the females live only long enough to birth their young before dying.
The animal that never dies is the Jellyfish or more specifically the Jellyfish Turritopsis dohrnii.
Turritopsis dohrnii, also known as the immortal jellyfish, is a species of small, biologically immortal jellyfish found worldwide in temperate to tropic waters.
A tiny jellyfish named Turritopsis dohrnii is capable of living forever, Motherboard reports.
Only discovered in 1988, the organism can regenerate into a polyp—its earliest stage of life—as it ages or when it experiences illness or trauma.
While an immortal jellyfish can age in reverse, it can also be easily killed by predators including various fish, sharks, turtles and even other jellyfish.
Of course, Turritopsis dohrnii isn't truly 'immortal'.
They can still be consumed by predators or killed by other means.
However, their ability to switch back and forth between life stages in response to stress means that, in theory, they could live forever.
In nature, most Turritopsis dohrnii are likely to succumb to predation or disease in the medusa stage without reverting to the polyp form.
The capability of biological immortality with no maximum lifespan makes T.
There are two main ways that jellyfish reproduce and if the conditions are favorable they can do this daily.
There are a few jellyfish species that receive sperm through their mouths to fertilize eggs inside the body cavity, but most jellyfish just release sperm or eggs directly into the water.
T. dohrnii may bend the rules to rejuvenate itself, but it can't always cheat death.
For example, jellyfish, including immortal ones, are prey to other animals, such as fish and turtles.
Polyps are also practically defenceless to predation by animals such as sea slugs and crustaceans.
Turritopsis dohrnii, the so-called "immortal jellyfish," can hit the reset button and revert to an earlier developmental stage if it is injured or otherwise threatened.
Like all jellyfish, Turritopsis dohrnii begins life as a larva, called a planula, which develops from a fertilized egg.
Jellyfish and sea jellies are the informal common names given to the medusa-phase of certain gelatinous members of the subphylum Medusozoa, a major part of the phylum Cnidaria.