From the one that's immortal to the one that's longer than a blue whale, these jellyfish facts will show you the strangest of the bunch.
Even among the one million ocean species we know of and the nine million we don’t, jellyfish truly are the ancient aliens of the sea. They’ve been swimming Earth’s oceans for over 500 million years — and that’s just the beginning. Discover more wonderfully weird jellyfish facts below:
For starters, jellyfish aren't actually fish, since they are invertebrates. For this reason, many people think they should be called "sea jellies" instead.Derek Keats/Flickr
Because of its incredibly think skin, a jellyfish can get its oxygen from diffusion, and therefore doesn’t need a respiratory system.Irene Grassi/Wikimedia Commons
Jellyfish are literally boneless, brainless, and heartless, and most are transparent.Sonnymt/Wikimedia Commons
Though they might not have brains, jellyfish do have a nervous system, or, nerve net, with receptors that can detect light, vibrations, and chemicals in the water. Nick Hobgood/Wikimedia Commons
Some jellyfish have ocelli, which are eye-like organs that are light-sensitive and can detect up and down motions. Ocelli appear as dark pigmented spots on the jellyfish. JOE KLAMAR/AFP/Getty Images
The box jellyfish has more advanced vision: its 24 eyes give it a 360-degree view of its environment. It is also the world's most dangerous jellyfish, and the most venomous marine creature. Certain species of box jellyfish can kill a person in just a couple of minutes. Peter Southwood/Wikimedia Commons
Most jellyfish are found in warm, shallow coastal waters, but there are a few species that live in the cold depths of 30,000 feet. Marsh Youngbluth/Wikimedia Commons
Jellyfish can reproduce both sexually and asexually. KENPEI/Wikimedia Commons
More than any other creature, jellyfish rule the water. The scyphozoan class of jellyfish are found in every ocean in the world, and the hydrozoan class can flourish in freshwater lakes and ponds. OpenCage/Wikimedia Commons
Green fluorescent proteins (GFPs) from the Aequorea victoria jellyfish species have transformed bio-medical research. The glow-in-the-dark proteins can illuminate specific proteins within the human body to track microscopic activity (for instance, cancer growth).Pixabay
Jellyfish spawn at around the same time every day, usually dusk or dawn. Nataliia Tydir/Getty Images
Most jellyfish live a relatively short life that ranges from a few days to less than a year. Some of the more minuscule only live for a few hours. YASSER AL-ZAYYAT/AFP/Getty Images
Jellyfish are between 95 and 98 percent water.iSpawn/Getty Images
Despite their poisonous defenses, jellyfish have many predators. Sharks, tuna, swordfish, sea turtles, and even salmon have been known to prey upon the jellyfish. Riza Nugraha/Wikimedia Commons
Considered the largest jellyfish species, the lion’s mane jellyfish (Cyanea capillata) can have tentacles that extend longer than a blue whale, the largest mammal on Earth.Kip Evans/Wikimedia Commons
Though some argue that the Nomura’s jellyfish (Nemopilema nomurai), which is found in the waters near Japan, Korea, and China, is the largest jellyfish. At their biggest, Nomura’s jellyfish can reach 79 inches in bell diameter and up to 440 lbs. in weight. Janne Hellsten/Flickr
Jellyfish have been in the water for more than 500 million years. They beat the dinosaurs by a long shot, making them the world’s oldest multi-organ animal. YOMIURI SHIMBUN/AFP/Getty Images
There are nearly 4,000 different types of jellyfish in the world with hydrozoa jellyfish accounting for at least 3,700 of them. Intandem/Wikimedia Commons
Environmental stress is believed to be the cause of jellyfish overpopulation. Climate change, pollution, dams, and overharvesting of fish have made it difficult for most other sea creatures to survive, but the adaptive nature of the jellyfish allows it flourish. FRED TANNEAU/AFP/Getty Images
After it was accidentally introduced into Eastern Europe's Black Sea, the comb jellyfish spread rapidly, took over, and wiped out the sea’s $350 million fishing industry, consuming ten times its body weight in food in a single day.Vidar A/Wikimedia Commons
Watch out—a jellyfish tentacle can sting even if it’s separated from the body. Luc Viator/Wikimedia Commons
On average, jellyfish kill more people than sharks do. Volkan Yuksel/Wikimedia Commons
The closer a jellyfish is to the water’s surface, the more likely it is to be colorless. Conversely, jellyfish that swim deeper tend be more colorful. Daniel Chodusov/Flickr
Sometimes, crabs will catch a ride on a jellyfish. The tough shells protect the crabs from the jellyfish’s stinging tentacles. Dan90266/Wikimedia Commons
A group of jellyfish is called a bloom, a swarm, or a smack. A large bloom can contain 100,000 jellyfish.Pixabay
A jellyfish is one of a few sea creatures that can adapt to ocean dead zones where there is lots of pollution but very little oxygen. Eric Kilby/Flickr
Because jellyfish feed on fish eggs and larvae, it’s extremely difficult for fish stocks to restablish themselves in marine ecosystems that are dominated by jellyfish. Eric Kilby/Flickr
Fishermen harvest jellyfish for their collagen, which has many medical uses including the treatment of rheumatoid arthritis. JOE KLAMAR/AFP/Getty Images
The umbrella-like bodies of jellyfish allow them to pulse their way around the water. This unique movement is called passive energy recapture, and makes jellyfish the most energy efficient swimmers, allowing them to travel 30 percent farther per swimming cycle than they otherwise would be able to.Pixabay
A military drone jellyfish named "Cyro" was engineered to conduct underwater military surveillance. The drone's design mimics the energy efficiency of a jellyfish, and can operate autonomously in the ocean. Wikimedia Commons
Jellyfish are passive hunters. Using their tentacles as a net, jellyfish capture prey such as plankton, fish, and crustaceans without much effort.Sanjay Acharya/Wikimedia Commons
Contrary to popular belief, urinating on a jellyfish sting is ineffective. Pixabay
For most jellyfish stings, salt water is the recommended fast-acting treatment, as it does not encourage the release of venom. Fresh water usually has the opposite effect, causing the continuous release of venom. Pixabay
The immortal jellyfish (Turritopsis dohrnii) ages like Benjamin Button: when a crisis like starvation presents itself, the jellyfish’s cells transform and revert to their earliest form, a polyp, making this type of jellyfish potentially immortal. (Immortal jellyfish not pictured) Harald Hoyer/Wikimedia Commons
Certain non-poisonous species of jellyfish are considered a delicacy in various parts of the world. The Cannonball Jellyfish is the most common cuisine jelly. Mr.TinDC/Flickr
Next, check out the newly discovered glowing jellyfish and see what it looks like to dive with millions of jellyfish. Then, discover seven of the most frighteningly bizarre ocean creatures. Finally, meet some of Earth's most lethal animals.
