Have you ever been stung by a jellyfish? Maybe not recently, since it’s winter, but on a summer beach trip?
I definitely have, because I go with my family most summers to Hilton Head, where you have to look out for jellies. Sometimes we also see them washed up on the shore. I’ve been thinking about jellyfish because I recently read a book called The Thing About Jellyfish. It’s a novel, not a nonfiction book, but it includes a lot of interesting jellyfish facts. For example, jellyfish are the oldest multicellular animals on earth, older than dinosaurs. But jellyfish aren’t fish, they’re plankton. Even though most plankton are very small, these invertebrates aren’t categorized as plankton because of their size. What makes them plankton is the fact that they drift around with tides and currents (the word “plankton” comes from the Greek word for drifter).
Yesterday I decided to do some research about jellyfish, and I learned some amazing facts that I want to share with you.
But before we get into talking about jellyfish species, we need to talk about the life cycle of jellyfish. Jellyfish start their lives as planula, which develop from eggs. The planula sinks to the sea floor or attaches to coral and then grows into a cylindrical formation of polyps. Those polyps detach and turn into genetically identical medusae, AKA jellyfish. Jellyfish drift with currents, but they do swim, inflating and then constricting their bells to move the water. This is called undulation. Jellyfish are some of the most efficient swimmers in the ocean!
There are more than 4000 species of jellyfish. The largest one is the lion’s mane jellyfish, which can be up to 120 feet long from the top of its bell (the round, umbrella-like body) to the end of its tentacles. The smallest jellyfish is the Irukandji box jellyfish, which is the size of a sugar cube.
Want to guess which one is more dangerous?
If you guessed the Irukandji jellyfish, then you are correct. This tiny jellyfish may look harmless, but it is actually one of the most dangerous jellyfish in the ocean! It’s a species of box jellyfish—some kinds of box jellies can kill humans within minutes. Some victims of Irukandji jellyfish have reported a sense of impending death, and have reportedly pleaded with physicians to kill them just to “get it over with.” (I learned this from the novel I read—it’s kind of a bummer, or at least it made me very emotional.)
The Australian box jellyfish are the most dangerous sea creatures. There are thirty to fifty species of box jellyfish, which are given their name because of their cube-like bell. They dwell in the Indo-Pacific ocean and along the coastal waters of Australia and produce a venom that is very painful, and sometimes fatal. In fact, each box jellyfish has enough venom in its tentacles to kill sixty humans! Recently, scientists in Australia used the gene-editing technology known as CRISPR to study these creatures, which helped them develop an effective antivenom. I still wouldn’t want to swim near any box jellies!
Did you know that some jellyfish live in fresh water? There’s a species native to China called Craspedacusta sowerbyi, AKA peach blossom fish or simply freshwater jellyfish. They were discovered in the Yangtze River but have spread to other parts of the world, including the United States, where they are nonnative, or invasive—some have even been found in Western North Carolina. In China, these jellyfish are endangered because of water pollution. Overall, jellyfish populations are increasing because of climate change (many like warm waters), and overfishing of animals they compete with for food.
About half of jellyfish are also bioluminescent. That means that they make their own light. They do this because most of them live in the deep sea, where it is very dark. Check out the firework jellyfish, which lives off of Baja California:
And if you want to know why I want to be a marine biologist when I grow up, watch this video:
Aren’t those beautiful?
But the most special kind of jellyfish is the Immortal jellyfish, which can biologically live forever.
Once Immortal jellyfish have grown to adulthood and reproduced, they go through a process called transdifferentiation. They sink to the sea floor, and slowly revert their specialized cells back to younger cells. They become a polyp again, and start their life cycle all over. They can do this forever—their life span is indefinite, because no immortal jellyfish has died of old age. Other cool facts about Immortal jellyfish are:
-They were first discovered in 1883, but it wasn’t until the late 1980s that scientists discovered their immortality.
-When Immortal Jellyfish reach the stage in their life cycle where they’re a medusa, they can choose to go one of two ways. They can continue to mature and spawn offspring, or they can revert back to polyp stage. Stress, sickness, or environmental changes can shock a medusa back to a polyp also.
Jellyfish are so important to the ocean ecosystem—they keep other species in check by feeding on eggs and larvae, and they are also food to other animals, especially sea turtles. Turtles don’t mind jellyfish tentacles, because their thick skin protects them from stings. By drifting through the different levels of the sea, jellyfish also help transport nutrients to animals and phytoplankton.
Have you ever seen a cool jellyfish? Which species is your favorite?
P.S. A note from Belle: Local readers can support public education in North Carolina at a rally this Thursday, February 23, at the NC State Capitol in downtown Raleigh. This day of action (10AM-2PM) is demanding that the state affirm and release the Leandro decision funds, to ensure “the constitutional right of North Carolina children to the opportunity to a sound basic education.” Leandro funds would go a long way to giving kids in every public school access to well-qualified teachers, principals, school nurses, and counselors; adequate facilities, technology, and materials; quality pre-K programs; clubs and after-school care, and much more. You can find out more here, and go for the whole day, or just part of the day. Hope to see you there!
Thank you for an wonderfully informative and fascinating edition of the FTT. I loved the videos. I was not aware that there were any immortal species. You have blown my mind today! My love to all of you.
Thank you, Bea. I didn't know about the immortal jellyfish! I am so glad you wrote this for us. I met a Physalia physalis once (just like your Mamie) and they gave me a hug around the stomach. Ouch.