2. Jellyfish reproduce both asexually and sexually. They are usually male or female, though hermaphroditic species have also been found.
3. Even a dead jellyfish can sting.
4. Jellyfish are invertebrates, which means they are animals without a skeleton. Approximately 95% of their body is water.
5. Jellyfish have lived in the waters of the world for more than 650 million years, long before the dinosaurs, making them the oldest multi-organ animal.
6. Jellyfish move in essentially two ways. They take water in their bell and then squirt it out behind them, which creates a jet of water that moves them forward. They also drift on water currents.
7. Jellyfish range from the size of a thimble or the eraser tip of pencil to approximately 8 feet in diameter and tentacles that reach 200 feet. That is as long as two blue whales.
8. The jellyfish’s main defence mechanisms are its stings and its transparent body, which makes it easy for it to hide.
9. Each jellyfish tentacle is armed with thousands of cells called cnidoblasts. Inside the cnidoblasts are nematocysts, each of which contains a coiled stinging thread. When a fish or other object becomes tangled in the tentacles, the pressure inside the nematocysts causes the venomous threads to uncoil like a spring-loaded harpoon.
10. Jellyfish do not have brains, hearts, ears, heads, feet, legs, or bones. Their skin is so thin that they can breathe through it.
11. A jellyfish tentacle can still sting even if it is separated from the jellyfish’s body.
12. Most jellyfish are passive carnivores. They feed on plankton, crustaceans, other jellyfish, fish eggs, and small fish. They eat and void through the same hole in the middle of the bell.
13. Jellyfish are usually seen in shallow coastal water; however, scientists have discovered a few species that live at depths of 30,000 feet (9,000 meters). While most jellyfish prefer warm water, some live in subarctic temperatures.
14. While jellyfish do not have a brain, they have an elementary nervous system with receptors that detect light, vibrations, and chemicals in the water. These abilities, along with the sense of gravity, allow the jellyfish to orient and guide itself in the water.
15. Jellyfish are harvested for collagen, which is used in a variety ways, including treating rheumatoid arthritis.
16. The uncoiling of the jellyfish’s small stingers is one of the fastest actions in nature. Stingers shoot out even faster than a bullet from a gun.
17. The largest jellyfish in the world is the Nomura’s jellyfish. Other candidates for the largest jellyfish are the Lion’s mane jellyfish and the Stygiomedusa gigantean.
18. Jellyfish have a short tube that hangs down from its body. The tube acts as both its mouth and its digestive tube. In some jellyfish, the central tube is surrounded by frilly pieces that look like curly ribbons in the water. These are called oral arms or mouth arms.
19. The smallest jellyfish in the world is the creeping jellyfish. It has bell disks from 0.5 mm to a few mm in diameter. It reproduces asexually by splitting in half. Another contender for the smallest jellyfish is the extremely toxic Australian Irukandji, which is only the size of a fingernail.
21. There are more than 2,000 different types of jellyfish. Approximately 70 can hurt people, with the box jellyfish (Chironex fleckeri) being the most dangerous. Scientists believe that there could be as many as 300,000 different species of jellyfish yet to be discovered.
22. Many scientists believe that environmental stressors—including climate change, pollution, overharvesting of fish, and dams—have led to the proliferation of jellyfish.
23. Jellyfish digest their food quickly. It would be difficult to float if they had to carry around large amounts of food.
24. Jellyfish that stay near the sunlight at the water’s surface tend to be colorless. Jellyfish that swim deeper are often red, purple, green, yellow, and sometimes they may even have stripes.
25. Scientists have developed antivenom for box jellyfish stings. In Australia, where box jellyfish live, ambulances and hospitals keep the life-saving compound on hand.
26. In several parts of the world, jellyfish are considered a delicacy. For example, in Malaysia, people call them “music to the teeth.” Approximately several hundred metric tons of jellyfish a year are eaten at $15 a pound, making it a multimillion-dollar business. The most commonly eaten jellyfish is the Cannonball jellyfish.
28. The type of jellyfish most seen on the shores of North America and Europe is the Moon jellyfish. This type of jellyfish is typically blue or pink and is found in waters approximate 20 feet (6 meters) deep. Its sting is usually mild, but can leave an itchy, red rash.
29. Many jellyfish have bioluminescent organs, which emit light. This light may help them in a number of different ways, like attracting prey or distracting predators.
30. If a jellyfish is cut in two, the pieces of the jellyfish can regenerate and create two new organisms. Similarly, if a jellyfish is injured, it may clone itself and potentially produce hundreds of offspring.
31. The movements of bell-shaped jellyfish have provided researchers with a new understanding of propulsion. The flexibility of their umbrella-like bodies allow them to pulse upwards and downwards without expending much energy. Researchers have created biomimetic robots with flexible bells, which may one day lead to better undersea vehicles.
32. It's probably not that surprising that jellyfish have served as inspiration for swimming robots. However, it's more unusual to see a sea creature inspire a flying machine, but that's just what happened at New York University.
33. A group of high school students in Japan came up with a salted caramel recipe that uses powered jellyfish. It's not vegan for sure, but it is one way to deal with an invasive jellyfish bloom.
34. Some jellyfish look like trash bags.They're known as Deepstaria enigmatica, and are usually found in the Arctic seas.
35. Another jellyfish-derived product takes advantage of the jellies' fluorescent protein, and could be used to power medical devices in the future.
36. In the past decade, jellyfish blooms have been responsible for shutting down several nuclear reactors, which often rely on ocean water intakes. The jellyfish swarms can clog the intake pipes, forcing facilities to stop operating temporarily.
37. Two Aquarists in Dallas, Texas created a peanut butter mix and fed it to moon jellies. Apparently, the jellies found this mix to be an acceptable source of protein. "We would love to claim we conducted this trial with noble purpose, but the truth is that we just wanted to make peanut butter for jellyfish simply to see if it could be done," the researchers write.
38. You may have heard that jellyfish are taking over the world's oceans. However, there's actually a good deal of debate about this issue among scientists.
39. Let's end this with a funny thing...Do you know why are jellyfish kept in round aquariums? Round aquariums prevent them from getting stuck in the corners!
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