Immortal jellyfish facts for kids
Quick facts for kids Immortal jellyfish |
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| Turritopsis dohrnii medusa | |
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Turritopsis
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dohrnii
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The immortal jellyfish, also known as Turritopsis dohrnii, is a super cool type of jellyfish found all over the world in warm and mild waters. What makes it special is its amazing ability to turn back into a younger stage after it has grown up. It's one of the only animals known that can do this!
Like most other jellyfish, T. dohrnii starts its life as a tiny, free-swimming larva called a planula. This planula eventually settles down and grows into a group of polyps that attach to the sea floor. All the polyps and jellyfish that come from one planula are exact copies, like clones.
These polyps grow into a bushy shape, which is a bit unusual for jellyfish. Then, tiny jellyfish (called medusae) bud off from these polyps and swim freely. When they are old enough, they can even eat other jellyfish! If a T. dohrnii jellyfish gets stressed, hurt, sick, or old, it can change back into a polyp. This happens through a special cell process called transdifferentiation, where its cells change into new types of cells.
In theory, this process can go on forever, making the jellyfish "biologically immortal." This means it doesn't die of old age. However, in real life, most Turritopsis dohrnii jellyfish are still eaten by other animals or get sick before they can turn back into a polyp.
Because of its amazing ability to live forever (in theory!), T. dohrnii is very important for scientists who study aging and medicine.
Contents
About the Immortal Jellyfish
Naming and Discovery
This special jellyfish was named in 1883 to honor Anton Dohrn. He was the person who started the Stazione Zoologica Anton Dohrn in Naples, Italy. For a while, scientists thought this jellyfish was the same as another type called Turritopsis nutricula, but now they know it's its own unique species.
What Does it Look Like?
The Turritopsis dohrnii jellyfish looks like a bell. It's usually about 4.5 millimeters (about 0.18 inches) wide, which is roughly the size of a ladybug! It's also about as tall as it is wide. The jelly-like part of its body is thin, except for a slightly thicker top.
Its stomach is bright red and shaped like a cross when you look at it from the side. Young jellyfish have only eight tentacles around their edge. But adult jellyfish can have 80 to 90 tentacles! These jellyfish swim freely in the ocean. They also have a network of nerve cells in their cap, which helps them sense things.
Turritopsis dohrnii also has a bottom-living polyp form. This part looks like tiny branches that grow along the sea floor. These branches have feeding polyps that can create new jellyfish buds. These tiny jellyfish, about 1 millimeter (0.04 inches) big, then swim away from the polyp colony after a few days.
Where Do They Live?
Turritopsis jellyfish are thought to have first appeared in the Pacific Ocean. But they have traveled all over the world, even through the Arctic! They have now spread to warm and mild parts of all the world's oceans.
Scientists believe these jellyfish are spreading because of ballast water. This is water that ships take in and release to help them balance. Unlike other animals that invade new places and cause big problems, T. dohrnii is so tiny and harmless that its spread often goes unnoticed. One scientist called it a "worldwide silent invasion."
Life Cycle and Immortality
How They Grow
Fertilized eggs of the immortal jellyfish grow into tiny larvae called planulae. These larvae then settle down on the sea floor or even on floating docks. There, they grow into colonies of polyps, which are like tiny plants.
These polyps then bud off new jellyfish, which are about one millimeter in size when they are released. The young jellyfish then grow and eat tiny ocean creatures. They become ready to reproduce after a few weeks. For example, if the water is 20°C (68°F), it takes 25 to 30 days. If it's 22°C (72°F), it takes 18 to 22 days. T. dohrnii jellyfish can live in water temperatures between 14°C (57°F) and 25°C (77°F).
The Secret to Biological Immortality
Most jellyfish species have a set lifespan, which can be from a few hours to many months. But the Turritopsis dohrnii jellyfish is the only one known that can turn back into a polyp! This special change needs certain types of cells from its body.
Scientists have done experiments to see how this works. They found that jellyfish of all ages, from newly released to fully grown, can change back into polyps. This happens if they are starving, if the water temperature changes suddenly, if the saltiness of the water changes, or if they are hurt.
When a jellyfish starts to change, its bell, jelly-like middle, and tentacles begin to break down. Young jellyfish (with 12 tentacles or less) first turn into a tiny, protective ball called a cyst. Then, they grow into polyps. However, about 20% to 40% of adult jellyfish can go straight to the polyp stage without forming a cyst. The polyps start to grow after about two days and can then eat food. These polyps can then make more polyps and branches, forming a whole colony.
In experiments, these jellyfish would eventually turn back into polyps and start their lives over again, even without any changes in their environment or injuries.
This amazing ability to reverse their life cycle is unique in the animal kingdom. It allows the jellyfish to avoid dying of old age, making Turritopsis dohrnii potentially biologically immortal. We don't often see this process happening in nature because it happens very quickly. Also, most individual jellyfish are likely to be eaten by predators or get sick before they can use their special ability.
Scientists are very interested in how this jellyfish's cells change. They hope to learn from it to find ways to make new stem cells for humans. This could help repair damaged or dead tissues in our bodies.
Life in the Ocean
What They Eat
Turritopsis dohrnii are meat-eaters. They mostly eat tiny ocean animals called zooplankton. Their diet also includes fish eggs and small mollusks. Like other jellyfish, T. dohrnii eats food and gets rid of waste through the same opening, its mouth.
They hunt by letting their tentacles drift through the water. These tentacles have stinging cells called nematocysts. When prey touches them, the tentacles sting it. Then, the tentacles bend to bring the food to the jellyfish's mouth. T. dohrnii can also use its bell to catch food. As it swims, its bell expands, sucking in water. This brings potential prey closer to its tentacles.
Who Eats Them?
Like many other jellyfish, Turritopsis dohrnii are often eaten by other jellyfish. Other animals that prey on them include sea anemones, tuna, sharks, swordfish, sea turtles, and even penguins! Many animals eat jellyfish because they are mostly water. They are only about 5% solid matter. They have three layers: an outer layer (epidermis), a middle jelly-like layer (mesoglea), and an inner layer (gastrodermis).
Where They Live
Turritopsis dohrnii was first found in the Mediterranean Sea. But, as we learned, it has now spread all over the world. These jellyfish usually live in warm to mild waters. You can find them in marinas, docks, on the bottoms of boats, and on the ocean floor. They typically live in water that has a certain amount of saltiness, from moderately salty to very salty.
Keeping Them in the Lab
It's quite hard to keep T. dohrnii alive in a lab. Only one scientist, Shin Kubota from Kyoto University in Japan, has managed to keep a group of these jellyfish alive for a long time. He has to check their food every day to make sure they are digesting it properly.
Kubota once reported that his colony of jellyfish went through their "rebirth" process 11 times in two years! Shin Kubota often appears on Japanese TV to talk about his immortal jellyfish. He has even recorded several songs about them, which he sometimes sings at the end of his science presentations!
See also
In Spanish: Medusa inmortal para niños
- Hydra – another kind of animal that is also said to be immortal
