Jellyfish are gelatinous creatures that belong to the Phylum Cnidaria of the class Scyphozoa (a group of invertebrate that consists of almost 200 different species). They are found in both deep and shallow waters. They are beautiful, diverse creatures that have roamed the seas for at least 500 million years.
Jellyfish Actually A Fish?
'Jellyfish' or 'Sea Jellies' is more of a broad, umbrella term of thousands of species and two different phyla. Unlike all fish who have a vertebrae, jellyfish are dome-shaped invertebrates. They derived their common name 'Jellyfish' from the jelly like substance they are made out of called 'Mesoglea'. Jellyfish is more closely related to corals, sea anemones, hydrozoans because they all possess a distinctive body part - a harpoon shaped stinging cell used to capture prey. It is common for animal of the phylum cnidaria.
What are Jellyfish made of?
Boneless, bloodless and brainless, jellyfish is nothing more than a blob of water. This is because a jellyfish is 95% water, compared to an average adult man who is 60% water. If they ever wash up on a beach they will most likely evaporate because of the high water content. But they are much more simpler than humans as they don't have hearts, brains or bones.
They are composed of three layers -
- An outer layer called the epidermis
- A middle layer made of thick, jelly like substance called the mesoglea
- An inner layer called the gastrodermis.
They have an elementary nervous system in their bells and tentacles that helps them to smell, detect light and respond to any other stimuli. They also a have a simple digestive cavity that serves both as a stomach and an intestine. Also like all members of the phylum, jellyfish shows a 'radial symmetry' that allows it to detect food and danger even from a distance.
Immortal Jellyfish
The "Turritopsis Dohrnii" or the immortal jellyfish is the only animal in the world to be able to reverse its ageing process also called Transdifferentiation. A fully grown Turritopsis Dohrnii is about 0.18 inches tall. A bright red stomach is visible in the middle. The bell is lined up with 90 white tentacles. When under stress, the jellyfish reverses its life cycle and goes back to being a polyp. This way it can start its life cycle all over again.
Are jellyfish harmful to Human beings
All jellyfish produce al least some type of toxins but not all are harmful to humans. Jellyfish have the ability to sting with their tentacles. The severity of the sting but mostly, jellyfish stings cause only minor discomfort.
Box jellyfish are the most venomous marine animals in the world and out of those the "Australian Box Jellyfish" has stingers and is considered the most venomous marine animal in the world. Its lethal tentacles can grow up to 10 feet long. The sting of the jellyfish can cause - paralysis, cardiac arrest or death in just a few minutes.
Jellyfish has limited movement over their movement since they use a single muscle - their bell which expands and contracts in order for them to travel short distances. This is the reason why they travel in large groups called a "bloom" , a "swarm" or a "smack". A jellyfish bloom forms quickly and according to scientists these congregate during mating season. The blooms can be so dense at a time, there are more jellyfish than water. Blooms can cover even as far as a hundred miles.
Jellyfish blooms are natural but can cause problems like - disrupting fisheries, making water unpleasant for swimming, closing beaches, destroying ships and and wreaking havoc in power plants.
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