A jellyfish is an aquatic group of animals found in every ocean of the world. It is soft-bodied and also a free-swimming animal with a gelatinous umbrella-shaped bell and trailing tentacles. Jellyfish can also be found in some ponds or freshwater lakes. While most jellyfish species are often found in shallow coastal waters, some species live in the very depths of the oceans. Jellyfish are believed to be the oldest multi-organ animal species in the world dating back to at least 500 million years back and possibly even 700 million years more.
Size And Characteristics
Jellyfish species vary greatly in size, ranging from the eraser tip of a pencil to about eight feet in diameter. Their tentacles, on the other hand, can reach up to 200 feet. This height can be compared to that of two blue whales. Each tentacle is equipped with thousands of cells known as cnidoblasts which contain nematocysts inside. Each nematocyst contains a stinging thread that is coiled. When fish or any other object is tangled in the tentacles, the pressure within the nematocysts makes the venomous threads uncoil. Therefore, the main defense mechanism of the jellyfish are it's stingers. The tentacle of a jellyfish can still sting even if it is separated from the animal’s body. It's transparent body makes it easy to camouflage. The skin of jellyfish is so thin that they can breathe through it, and they do not have bones, brains, or hearts.
Different Species Of Jellyfish
There are more than 2,000, different types of jellyfish around the world. However, scientists believe that there could be as many as 300,000 different species that are yet to be discovered. Of the 2,000-known species, only 70 can be harmful to human beings. The box jellyfish (Chironex flecker) are among the most dangerous. Turriptosis nutricula is a species of the jellyfish commonly referred to as the ‘immortal jellyfish’ since it can transform into the polyp state from the mature medusa thus avoiding death. The immortal jellyfish can accomplish this through a cell development process known as transdifferentiation. The Moon jellyfish is a type of jellyfish often seen on the shores of Europe and North America, it is typically pink or blue and is found in water approximately 20 feet deep. However, the Moon jellyfish has a mild sting which can leave a red, itchy rash. The world’s largest jellyfish species are the Nomura’s jellyfish, the Stygiomedusa gigantea, which has only been seen 17 times in the last 100 plus years, and Lion’s Mane Jellyfish. On the other hand, the creeping jellyfish is the world’s smallest jellyfish species.
About 150 million people around the world are exposed to jellyfish every year. Approximately 200,000 people are stung in Florida every year and another 500,000 people around Chesapeake Bay. Approximately 100 human lives are lost per year as a result of jellyfish stings in different parts of the world such as Australia, Thailand, Philippines, and Indonesia. In Japan, jellyfish have single-handedly managed to temporarily shut down a nuclear power plant after they were stuck in the cooling system. While environmental stressors threaten many animal species with extinction, they may increase jellyfish swarms because these species are one of the few that can easily adapt to zones where there is a lot of pollution and little oxygen.