Original photo by DKart/ iStock
While we humans can quite happily sit out in the sun for hours (with adequate sun protection, of course), jellyfish can disappear completely if washed ashore on a sunny day. This is because a jellyfish’s delicate body is composed of at least 95% water, unlike the human adult body, which is about 60% water.
Oops, incorrect!
It's a factJellyfish have been around for more than 500 million years, possibly even as long as 700 million years, meaning they appeared more than 250 million years before the first known dinosaurs. This gives jellyfish the distinction of being the oldest multi-organ animals in the world.
As you may suppose, jellyfish are jellylike in consistency — at least when well hydrated — but they aren’t actually fish. They are in fact plankton, ranging in size from less than an inch to nearly 8 feet long, with tentacles that can measure an impressive 100 feet or more. (The largest jellyfish is longer than a blue whale.) Jellyfish have no bones, no brain, and no heart, and they use only rudimentary sensory nerves at the base of their tentacles to detect light and odors.
Due to their structure and exceptionally high water content, jellyfish can evaporate within hours in a process known as deliquescing if they’re stranded on a beach in the sun. The jellyfish shrinks as its water evaporates away, leaving behind nothing but a faint imprint on the sand.
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Box jellyfish rank among the ocean’s deadliest creatures.
When we think of dangerous sea creatures, our minds tend to jump straight to sharks. In reality, there’s a far greater threat floating in the open water: the box jellyfish. These nearly transparent creatures possess up to 15 tentacles, each growing to roughly 10 feet in length.
Each tentacle has about 5,000 stinging cells, whose venom is considered to be among the most potent and deadly in the world. While typically used to instantly stun or kill prey such as fish and shrimp, a box jellyfish’s venom can also be fatal to any humans who come too close. The sting is so unbearably painful that human victims have been known to go into shock and drown — or die from heart failure — before even reaching the shore.
While there are an average of six fatalities from shark attacks per year, box jellyfish stings result in between 40 and 100 human fatalities annually, although experts believe the true figure is likely far higher. As such, box jellyfish can claim to be the deadliest creatures in the ocean.
Tony is an English writer of nonfiction and fiction living on the edge of the Amazon jungle.
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