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Jellyfish, also known as jellies, are members of the Cnidaria phylum and Medusozoa subphylum.
Other members of the phylum are corals, sea whips and sea anemones. In other languages like Spanish, they are called medusa.
There are 200 different jellyfish species on the planet. The jellyfish looks like a bell with hair-like structure hanging from it. These hair like structures are called tentacles. They use their tentacles to sting people and other predators. A jellyfish sting can be life threatening. The box jelly is the most dangerous one. A group of jellyfish is called a bloom, swarm, or smack and can have as many as 300,000 jellyfish. These free swimming animals have a complex lifecycle. Jellyfish can survive in almost any water source. The diet of a jellyfish is simple. It eats small plants, shrimp, or fish. Some jellies can also glow in the dark due to the presence of a protein known as the bioluminescent protein. We have curated a bunch of interesting facts about jellyfish. You can also check out our other articles on what is a group of jellyfish called and how do jellyfish reproduce for more great content.
Jellyfishes are some of the few animals that do not have a centralized brain. Shocking, right!
Jellyfish do not have a heart or bones either.
How jellies manage to survive without a central brain is just fascinating. People all over the world are blown away by the fact that these squishy creatures are able to carry out all the normal day to day activities like hunting, eating, and moving even in the absence of the complex organ that controls the whole body of animals and humans, the brain.
All the body parts of a jellyfish are placed along the axis of a center point. This is common in all members of the phylum. The radial symmetry of the body parts helps the jellyfish perceive and react to food. This also ensures that they react to threat from all directions ad protect themselves using their tentacles. Locomotive commands are given by the brain. These creatures travel easily by using different techniques. On the end of the bell of a jellyfish, there are finger like structures called rhopalia. The rhopalia have a small spot of pigment that has light sensitive cells which help the jellyfish to sense light and move accordingly. Rhopalia performs the function of the ears, eyes, and cerebellum. Each jellyfish fish has four rhopalia. Some jellyfish species like the box jellyfish have unique, well developed eyes which make swimming a cakewalk for them.
Did you know? The box jellyfish has six eye clusters with each cluster having four eyes. Two of these eyes are complex and have lenses. The other two have pigment spots to sense light.
Now, you might be thinking that a jellyfish is nothing but a dumb marine creature. It is only fair if they are considered unintelligent, after all, they lack the most important organ that is used to define and measure intelligence.
They are quite unintelligent compared to other fish and animals in the sea. They do not have complicated organs. They just have a basic set of nerves in their body. Hence they do not exhibit any advanced behavior. They do not have the ability to think, store and process information. Unlike other animals which use their brain to function efficiently, the jellyfish is focused and built for survival. These basic sets of nerves are more than enough to help them perform day to day activities for survival. But some people have a different opinion. They think that jellyfish are actually doing quite well for an animal with no brain. Whether a jellyfish is intelligent or not actually depends on how you look at it.
Did you know? When a jellyfish is cut in half, the two halves can turn into two separate jellyfish.
Instead of a brain, the jellyfish has a primary set of nerves also known as the nerve net. The nerve net is radially spread throughout the body of the jellyfish under the epidermis.
The jellyfish is able to detect the light, smell, and even carry out a few other activities with the help of the nerve net. How does the jellyfish maintain balance even if it does not have a brain? This is one of those questions that will keep you up at night. But don't worry scientists have figured out how they manage to do this. The jellyfish has a sensory machine beside its eye. The organ of balance in the jellyfish is called statocysts. It contains sand grains. Due to the extra resistance created by the fluid flow when jellyfish travel, the grains fall on the sensory neurons. The direction of motion and sensory neurons are in opposite directions. The reflexive movements in response to the information obtained from the above mentioned action allow the jellyfish to change and correct its trajectory.
The nerve net and sensory organs provide rudimentary information that tells the jellyfish what to do and how to move.
They have the nervous systems in place of the brain. This carries out the basic functions that are to be carried out by the brain.
The main function of the heart in an animal is to pump blood to other organs and carry out respiratory functions. Jellyfish do not have blood in their system. Hence they do not need the heart to pump blood to the rest of the body. The skin of a jellyfish is very thin. The skin allows them to absorb oxygen from the environment.
While there are several volumes of books on the anatomy of humans, the anatomy of jellyfish is actually very simple and truly only requires. They are one of the simplest invertebrates in the world.
95% of the jellyfish body is just made up of water while only 60% of the human body is made of water. Jellyfish are just squishy water balls that lack vital organs like the heart, brain, and blood. The human body is entirely different from that of the jellyfish. For humans, it is much more complicated and requires the brain, heart, and blood to function efficiently. The body of a jellyfish is made up of three layers; the epidermis (the outermost layer), mesoglea the middle layer made of thick, jelly, and the gastrodermis the inner layer. Humans have seven layers of skin, within which lies muscles and then bones. Jellyfish do not have bones and only some vital muscles that either help in the way they move and reproductive purposes. Humans, on the other hand, have muscles in all parts of the body. The nervous system of a jellyfish is just a grade one network when compared to the nervous systems of human beings. Not just this, but the digestive system is also the same. Unlike humans, these creatures do not have a stomach and intestine. They just have a digestive activity that serves as both the intestine and the stomach.
Did you know? Over 2,000 jellyfish polyps were sent to space in 1991. This was done to experiment with how they functioned in the absence of gravity. These 2000 jellyfish polyps not only survived by also reproduced. They were able to produce over 55,000 polyps. However, when they returned to earth they did not function properly.
Here at Kidadl, we have carefully created lots of interesting family-friendly facts for everyone to enjoy! If you liked our suggestions for jellyfish brain, then why not take a look at how do jellyfish eat, or jellyfish facts?
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