How do jellyfish die

Despite our many human endeavours to escape or delay the process of ageing, it seems to be an inevitable part of life. There is a word for it: senescence. At the cellular level, it means cells stop dividing and they eventually die.

It can also apply to an entire organism where a living thing can no longer respond adequately to outside stressors , or to specific organs or tissues like leaves dying and falling from trees in autumn.

While there are ways we can slow down or speed up the rate at which senescence occurs, it is still going to happen one way or another. However, a few species can escape the ageing process completely. These small, transparent animals hang out in oceans around the world and can turn back time by reverting to an earlier stage of their life cycle. A new jellyfish life begins with a fertilised egg, which grows into a larval stage called a planula.

It remains stuck in place for some time, growing into a little colony of polyps that share feeding tubes with each other. This process is responsible for the next stages of the jellyfish life cycle: the ephyra a small jellyfish and the medusa, which is the fully-formed adult stage capable of sexual reproduction.

For most other jellyfish, this stage is the end of the line. But Turritopsis dohrnii and possibly some other jellyfish species too has a neat party trick: when it faces some kind of environmental stress, like starvation or injury, it can revert back to being a tiny blob of tissue, which then changes back into the sexually immature polyp phase of life.

It is a bit like a butterfly turning back into a caterpillar, or a frog becoming a tadpole again. They spend this part of their lives as opaque drifting balloons with trailing tentacles. Jellyfish start their lives as larva, tiny cigar shaped creatures that spiral through the water, looking for a rock or something handy to attach itself to.

Once firmly in place, the larva metamorphoses into a polyp, rather like a tiny sea anemone. Colonies of these polyps are created as the polyp clones itself which means a colony can cover an entire boat dock in a matter of days.

Some types of polyp form huge shrub-like bushes. When the conditions are right, these polyps bloom in vast numbers and when they bloom, what buds from the polyp are baby jellyfish. When the medusa the immortal jellyfish Turritopsis dohrnii dies, it sinks to the ocean floor and begins to decay. Amazingly, its cells then reaggregate, not into a new medusa, but into polyps, and from these polyps emerge new jellyfish.

The jellyfish has skipped to an earlier life stage to begin again. This was a real mind blower for all of us In , moonfish jellyfish travelled into outer space on the Space Shuttle Columbia so that scientists could examine how microgravity affected them.

The jellyfish multiplied in space. When they came back to Earth, the scientists discovered that the space-born jellyfish couldn't figure out how to deal with gravity. Even though some jellyfish have very long tentacles, they never get tangled up or sting them.

It can have tentacles that are over 27 meters long - longer than the size of the blue whale which is the biggest mammal in the world!

You might think that a gaggle of geese, a murder of crows, or a clowder of cats sounds interesting, but jellyfish groups have even better names.