Jellyfish are a mystery to the world. They have so many fascinating attributes that are different from other sea creatures.
Jellyfish move together in a bloom. Their organs range from pink to blue, purple, and deep violet. “Jellies” do not have brains or a heart; they have something called a nerve net.
Their most common body shape is the medusa. It is one that looks like a bell or an umbrella. In some species, the medusa can be as small as one inch. The medusa is round and symmetrical. It allows the body to respond to signals about food or danger. No matter where the signals are coming from, it takes the same amount of time and energy to get to the jelly.
The Portuguese-man-of-war’s tentacles can reach up to 165 feet long, while other jellyfish’s tentacles are only a few inches. The top part of the Portuguese-man-of-war looks a lot like the sail on a famous ship called the Portuguese-man-of-war, and that is why they named the jelly after the ship.
The North Atlantic lion’s mane has 40-60 tentacles, stretching down 100 feet. Depending on the fish, there might be 60 tentacles reaching from 45 feet. Some can reach three times that length. The Portuguese-man-of-war and the North Atlantic lion’s mane are some of the biggest jellyfish there are. The North Atlantic lion’s mane can be up to eight feet long.
One of the differences between jellyfish and other creatures is that they do not have eyes. This can make it harder for bigger jellies to get food. They have to wait for a fish to accidently swim into their tentacles. Some bigger jellyfish will sometimes eat other jellies if they swim into their tentacles.
Small jellyfish get their food by rapidly beating their tentacles, pulling water and plankton to their arms. They then use their arms to pull the plankton near the mouth and their mouth scoops the plankton up off the arms and eats it.
Jellies’ most common defense is stinging. When an intruder, like a turtle or a fish, touches their tentacles, it triggers the jelly’s release of thousands of tiny, barbed stinging cells into the victim’s skin, scales, or shell. The animal is either shocked or killed, depending on the intensity of the jellyfish’s venom. There is one fish, called the Nomeus gronovii, that lives in the tentacles of the jelly called Portuguese-man-of-war without getting stung. It lives off of little bits of tentacles. It is one of the very few creatures that is not affected by the sting.
Most jellyfish are harmless to people, though some can cause very mild pain to us. There are very few species that are poisonous; the most poisonous of them all will nearly kill a person by stinging it. As we all know, humans kill far more sea life than sea life kills humans.
Swimmers in the coastal waters of Australia know to be cautious around the jelly called the sea wasp. The sting of the sea wasp is very similar to the sting of the Portuguese-man-of-war and may result in death. The jelly itself does not attack humans, but in situations where a human gets very close to its tentacles, it will shoot stinging cells into the human and within seconds will cause the following: an upset stomach, vomiting, and difficulty breathing. The person may die in a matter of minutes. Scientists have found some types of suits that will not trigger the stinging cells if a person goes near the tentacles.
The female jellyfish releases eggs into the water and they float away. In some species, the eggs will stick to the mother’s arms/tentacles until they hatch. After two to five days, the future jellyfish sinks to the ocean floor. A stalk grows from its body and attaches to anything solid on the seabed. The jelly larva is flat, with tiny tentacles around the perimeter of its body. They are like little paddles that help the tiny jelly swim away from its parent to start its life. The polyp stage is the first stage where they are hooked to the ocean floor. Some people believe that a jellyfish can live up to around five years in the polyp stage. But most do not. The medusa jellyfish can live up to a few months in the polyp stage.
Jellyfish are made of 90-95 percent water, depending on the species. That makes them very fragile, so they float in the water instead of being on land. The upside-down jellyfish does not float in water; it anchors itself to the ocean floor with its short arms and tentacles reaching up. It looks like a bowl of plants.
Jellyfish move by sucking in their tentacles then pushing off the water to move, as shown in the pictures below:
Jellyfish have been floating in the oceans for 650 million years. They’re one of the oldest creatures on the Earth. They were here before dinosaurs. I hope this helped you learn more about the fascinating creature, jellyfish.