Jellyfish sting for the same reason many sharks bite, they bump into something they think might be food and try and eat it. Are jellyfish conscious? Jellyfish have no brains and therefore are not aware of their own existence. So no, while alive they are not “conscious”.
Many jellyfish have circadian or daily rhythms, which mean they behave differently during day and night. “Fly one to Tokyo and it would get jet lag just like we do,” Helm says. With this seemingly primitive nervous system, one part of a jellyfish body can be aware of, and respond to, the needs of another part.
Jellyfish don't feel pain in the same way that humans would. They do not possess a brain, heart, bones or a respiratory system. They are 95% water and contain only a basic network of neurons that allow them to sense their environment.
Jellyfish are not very smart. “They have very simple sensory organs, and no brain to process any information,” says marine biologist Stein Kaartvedt.
They don't have any blood so they don't need a heart to pump it. And they respond to the changes in their environment around them using signals from a nerve net just below their epidermis — the outer layer of skin. It is sensitive to touch, so they don't need a brain to process complex thoughts.
Jellyfish don't usually mean to sting humans. They sting when you brush up against them while swimming or walking along the beach. Most jellyfish stings are harmless. But some jellyfish stings can cause serious harm.
They may not have a brain, but jellyfish do get stressed out when handled roughly, scientists find.
Jellyfish “do it” in so many ways! They never get bored. The male and female medusa of some species (there are thousands of species) shed eggs and sperm in similar localities. The eggs get fertilized and develop into swimming larvae, which transform into polyps.
These jellies can see blurry images. Not only do the complex eyes give a means to visually navigate their environments, but in some cases, they allow jellies to detect gravity. A crystal known as a “statolith” hangs under the eye, like a tennis ball hanging from a rope. As a result, they always knows which way is up.
Instead of a single, centralized brain, jellyfish possess a bodywide network of nerves that communicate with each other, allowing them to detect touch, temperature, salinity, and more.
HAPPY - Clear, open bells
The perimeter of the bell is smooth and open, not rigid and curled. The tentacles are relaxed and soft. Do not target feed your jellyfish on a daily basis. If your jellyfish cannot feed on their own, you need to look at what you are feeding and why you need to target feed them.
Jellyfish stings can be painful to humans and sometimes very dangerous. But jellyfish don't purposely attack humans. Most stings occur when people accidentally touch a jellyfish, but if the sting is from a dangerous species, it can be deadly. Jellyfish digest their food very quickly.
On average, jellyfish will live anywhere from 1-3 years. However, certain species will only live a few days while others are able to live for a few decades. However, scientists are unable to say definitively how long jellyfish live due to their complex life cycles.
The long tentacles trailing from the jellyfish can inject venom from thousands of microscopic barbed stingers. Most often jellyfish stings cause instant pain and inflamed marks on the skin. Some stings may cause more whole-body (systemic) illness. And in rare cases they're life-threatening.
MYTH #2: Jellyfish "go after" people
Not true. Any contact with jellyfish is incidental. Humans are not on their menu, but when we are in their environment we can get in the way of their tentacles.
Some things you can do to help prevent jellyfish stings include the following: Avoid swimming in the sea when there are warnings about jellyfish. Don't touch any jellyfish in the water or on the beach.
A jellyfish breathes by taking in oxygen from the seawater through its skin so as soon as it is on dry land it can no longer live.
Using electrophysiology, the spectral sensitivity curves of the lens eyes in Tripedalia and another box jellyfish had a peak at approximately 500 nm. That means that these lens eyes sense blue-green wavelengths of light.
"It may not seem surprising that jellyfish sleep—after all, mammals sleep, and other invertebrates such as worms and fruit flies sleep," says Ravi Nath, the paper's co-first author and a graduate student in the Sternberg laboratory. "But jellyfish are the most evolutionarily ancient animals known to sleep.
Yes, jellyfish sleep. And the weird part is that jellyfish have no brain and they can still sleep. How is that? Writing this week in the journal, Current Biology, researchers describe how they discovered this unexpected behavior in an upside down jellyfish.
Jellyfish are usually either male or female (with occasional hermaphrodites). In most cases, adults release sperm and eggs into the surrounding water, where the unprotected eggs are fertilized and develop into larvae.
The 'immortal' jellyfish, Turritopsis dohrnii
To date, there's only one species that has been called 'biologically immortal': the jellyfish Turritopsis dohrnii. These small, transparent animals hang out in oceans around the world and can turn back time by reverting to an earlier stage of their life cycle.
At the polyp stage, jellies resemble tiny anemones and reproduce asexually by strobilation. When a polyp strobilates—segmenting its body to reproduce—it releases tiny ephyra into the water. Within a few weeks, a bell appears and the ephyra are considered medusa, starting the whole process over again!
The longest-lived jellyfish is the aptly named immortal jellyfish Turritopsis dohrnii, a species of hydrozoan jellyfish native to the Mediterranean Sea and the waters off Japan, which can become quite literally immortal once it reaches adulthood.