Jellyfish consist of 95 percent water, but can still grow longer than a blue whale.

10 things you didn't know about jellyfish

They predate the dinosaurs, can become immortal and have been in space. Join us in the jelly-soft world of jellyfish.

Jellyfish consist of 95 percent water, but can still grow longer than a blue whale. Marine researcher Tone Falkenhaug explains some of the jelly animals' secrets.

1. Older than the dinosaurs

When you get stung by a jellyfish, you get to feel an animal that has existed for more than 500 million years.

"They arose before the fish, even before the dinosaurs. Jellyfish are among the oldest multicellular organisms we have on earth", says Falkenhaug.

According to the marine scientist, jellyfish are an evolutionary success story of great proportions. Fossils show that the jellyfish that existed millions of years ago are quite similar to the ones we have today.

"They found a winning formula early on. We can safely say that jellyfish are the world's oceans' most successful predators", she says.

2. Brainless and heartless

Jellyfish lack both a brain and a heart, but they are still able to eat large fish.

"They can sense smells and movements in the water, but most jellyfish do not hunt their prey", says Falkenhaug.

Instead, they are almost like spiders, spreading their tentacles and waiting for animals to be caught. It is the 40 meter long tentacles that make the jellyfish the longest of them all, even longer than a blue whale.

"Jellyfish don't have teeth or claws either. The burning nettle cells are the capture weapon that stuns the prey. Then they have a mouth between the tentacles where the food is fed in", says the marine scientist.

3. Go where the ocean currents take them

Jellyfish are plankton. That is, they operate with the ocean currents. But how far can they travel?

"It depends a bit. How far can a bottle mail drive? In theory, jellyfish can drift as far as an ocean current can carry them during a lifetime", says Falkenhaug.

Although jellyfish cannot control where they swim, they can control how deep they want to be. Thus, they can switch between different current directions at different depths.

"What controls the depth they are at is sufficient temperature and food availability", says the researcher.

4. Been in space

Jellyfish are found in all oceans and at all depths. There are even some species that live in fresh water.

"It is fascinating how adaptable they are. They can live in all environments in all oceans", says Falkenhaug.

But it does not stop there.

In 1991, 2,000 jellyfish were sent into space to see how they reacted to weightlessness. The results showed that jellyfish that grow up in weightlessness have major problems with movement and sense of direction, even when they return to earth.

"This has implications for any intergalactic journeys in the future. Children who are born and raised in weightlessness can have major problems for the rest of their lives with moving and coping with gravity on another planet", says Falkenhaug.

Jellyfish are incredibly adaptable animals, and can live in all environments in all oceans. (Photo: Christine Fagerbakke)

5. Make your own clones on the seabed

Jellyfish have two different life stages. Most people know them as floating jelly balls that can often get in the way of bathing.

"Our jellyfish and glass jellyfish usually only live through a spring and summer season", says Falkenhaug.

But before they die, the jellyfish have released larvae that swim down and attach themselves to the seabed as polyps. These polyps multiply by cloning. They release small saucer-like animals that develop into the regular jellyfish we know best.

"The polyps on the seabed can sit there for many years. They can simply sit and wait for better times", says Falkenhaug.

"This ability is probably the reason why the amount of jellyfish we see varies greatly from year to year", she adds.

6. The Immortal Jellyfish

There is one jellyfish that manages to reverse its aging. Turritopsis dohrnii , better known as the Benjamin Button jellyfish, can reverse its life cycle if stressed or exposed to danger.

"Then it swims to the bottom and attaches itself like an anemone. The mother jellyfish goes back to doing the same thing as the offspring", says Falkenhaug.

"And then it sits there on the bottom during the winter and clones itself into new jellyfish. Then it lives on in a way."

Physophora hydrostatica , also called the cave skirt jellyfish, is a colonial jellyfish that can find its way to Norwegian waters. (Photo: Øystein Paulsen / Institute of Marine Research)

7. Colonies with a good distribution of roles

There are also jellyfish that live close to each other. Very dense. They are called colonial jellyfish, and Portuguese warships are one example of such a species.

"Each member of the colony contributes with a specific task", says Falkenhaug.

One individual is a specialist in catching food, another individual is specialized in defending the colony, while others deal with reproduction or provide buoyancy and propulsion in the water masses.

"They are connected physically, and each individual cannot manage alone. They are almost like one organism, but it has not gone that far", says the researcher.

8. The world's most dangerous animal

Contact with the colony jellyfish Portuguese man-of-war can be very painful for humans, but there are jellyfish that are much, much more dangerous.

"The cube jellyfish is considered to be the world's most dangerous animal", says Falkenhaug.

The dreaded jellyfish, which lives in Asia and Australia, has enough venom to kill several people.

Tone Falkenhaug (TV) and Eli Gustad count jellyfish outside HI's research station in Flødevigen. (Photo: Espen Bierud / Institute of Marine Research)

9. Used in cancer medicine

However, jellyfish are not only dangerous. They can also help make people healthy.

Scientists discovered that the crystal jellyfish had a green fluorescent protein, which can make other proteins in the body almost luminescent.

"Today, this protein is used, among other things, in cancer treatment", says Falkenhaug.

"It seems so good that this jellyfish can take some of the credit for the scientists winning the Nobel Prize in chemistry in 2008", she adds.

10. Difficult animals to research

There is still much we do not know about the jellyfish. They are quite difficult to research.

"The main reason for that is that they consist of jelly. It is difficult to catch them with ordinary tools, because they break so easily", says Falkenhaug.

Since jellyfish are plankton, they are included in the Norwegian Institute of Marine Research's annual plankton monitoring, but the plankton researcher still has a request for the public.

"We cannot be everywhere at all times. So we want reports from people who come across large jellyfish blooms or jellyfish that are unusual in our latitudes", she says.

Author/Source: Anders Jakobsen / HAVFORSKNINGSINSTITUTTET (translated from original in norwegian)

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