Lesson Plan - Get It!
Have you ever thought about going back to when you were younger? Or wondered what would happen if a butterfly could go back to being a caterpillar?
These mind-boggling questions may not make sense to you now as you read this. But as you complete this lesson, you will see how similar these scenarios are to what happens to a living thing that is considered immortal, or something that lives forever!
Immortality is such a fictional term used to describe our fantasy with eternity. The idea of living forever plays out on the big screen with the wisecracking mercenary Deadpool and in the romantic Twilight series. Historically, the search for immortality can be seen in Ponce de Leon's search for the Fountain of Youth.
Scientists study regenerative medicine and how cells can be engineered to create immortality. Was it impossible to think they might discover a breakthrough among living creatures on earth? "Eureka!" as they say. Marine biologists found tiny creatures, living deep down in the Mediterranean Sea and the waters of Japan, that can live forever.
Let's explore the world of this tiny, transparent jellyfish and its death-defying journey to immortality!
The Immortal Jellyfish
What if you could live forever? Would you be excited or scared? Unfortunately, the average lifespan of humans on earth is only 79 years. We live and die - that's the reality of human life. But there is a way to live forever! The bad news is, you have to be a tiny floating blob of jelly to do so!
Turritopsis dohrnii is a species of jellyfish that has the unofficial name immortal jellyfish. Its discovery dates back to 1988 when a marine biology student collected them from the northwest coast of Genoa, Italy. Unintentionally, they were left soaking in a bowl of seawater for two days. When they were observed again, their original form had significantly changed! The jellyfish appeared as though they were gone, but each had actually just changed into a polyp!
- What is the polyp stage in a jellyfish's life?
Let us take a look at the life cycle of this jellyfish to have a better understanding of how they transform from one stage to another.
The Life Cycle of a Jellyfish
Image from Zina Deretsky of the National Science Foundation, via Wikimedia Commons, is in the public domain.
When adult male jellyfish release sperm, it fertilizes adult female eggs. These fertilized eggs become very tiny free-swimming larvae called planula, which is the larval stage. The planula swim around before sinking deep down to the ocean floor where they attach and form into colonies called polyps.
After a few days, tiny jellyfish about 1mm wide bud off from the tips of the polyp and float through the ocean. After two to four weeks, these grow to about 5
mm wide and become sexually mature male or female jellyfish called medusa. Then the cycle starts over.
There is an interesting deviation to this cycle, however, for the Turritopsis jellyfish. Once this jellyfish reaches its mature stage (medusa), it can revert back into the polyp stage!
They achieve this through a process called transdifferentiation. This is the ability of a mature cell to transform into another type of mature cell. There is no limit to how many times they can make these changes, and that makes them immortal! Check out this Turritopsis Life Cycle diagram from Discover Magazine to see the reverse cycle.
It is important to note, however, that this ability does not mean Turritopsis jellyfish cannot die. They can. For example, many are eaten by other sea creatures.
Watch How to Live Forever? Be a Jellyfish, from SciShow, to learn more about these amazing creatures:
Taking it further!
- Did you know that the mature jellyfish stage shares its name with the Greek mythological monster Medusa?
Medusa is generally described as a winged, human female with living venomous snakes in place of her hair. Jellyfish often look like a bell with tentacles all around the edge or hanging off the bottom. The shape of this bell is called a medusa because it looks like the Medusa in Greek mythology, which states she offended the goddess Athena who then changed her hair into snakes and made her face so hideous it turned people into stone.
There are other cool things that make jellyfish interesting. Look at the list below and check out the Additional Resources in the right-hand sidebar if you want to learn more!
- Jellyfish don't have brains. They respond to their environment by using a net of very sensitive nerves. Their skin is so thin that it can readily accept oxygen through itself.
- Some jellyfish have teeth. The beroid comb jellyfish have hundreds of rows of "teeth" made of tiny hairs that can pierce, tear, and pull their prey into their stomachs
- Jellyfish have gone to space. Jellyfish traveled into outer space on the space shuttle Columbia. They multiplied in space, but these new jellyfish could not figure out how to deal with gravity when they returned to Earth.
As you can see, jellyfish present scientists with a lot to study. The Turritopsis' transdifferentiation ability, however, is the most exciting. Researchers worldwide are trying to discover what happens to the jellyfish's cells when it goes through this transformation. Scientists believe that this species can hit the cell rewind button using a controlled pathway. Their goal is to discover what those pathways are.
The idea that old cells can renew themselves and go back to the stage where they can be young again is very exciting in the medical field. For many years, scientists have used stem cells in their research to provide hope and answers to our questions about cancer, Parkinson's, and other diseases. Turritopsis cells provide a whole new level for research.
- Have you learned something new and interesting?
Let's head over to the Got It? section and see how much you remember!