Feb 12, 20204 min read

Why are jellyfish so fascinating?

Updated: Feb 12, 2020

Blue blubber jellyfish, found in coastal regions in the Indo-Pacific — Photo by Eugenia Clara on Unsplash

The marine ecosystem has a fair share of strange creatures. Statistically speaking, this is understandable since the ocean is pretty diverse—it contains about 99% of the world’s biosphere. So, naturally, our oceans are bound to be the home to rare life. From the immense blue whales to the alien-like colossal squids, the astonishingly smart dolphins to the efficient deep-sea angler fish, our oceans have it all, but for me, creatures don’t get eerily fascinating than the jellyfish! I mean, they are not even fish for all we know.

The jellyfish are strange-looking creatures. Just like one could claim that octopuses are aliens, you could say the same thing about certain jellies as well. They are not your average sea creature by any stretch of the imagination. But what makes these animals so incredible?

They are older than dinosaurs

With their weird gelatinous bodies, jellyfish have been roaming the oceans for a very long time. But how long are we talking about here? A 2007 article on PLOS [1]reported a cnidarian jellyfish fossil that was 505 million years old, which means that these creatures have survived through major extinction events on our planet, including the Permian-Triassic extinction event [2], the biggest one in Earth’s history, that wiped out almost 96% of all marine species and 70% percent of all terrestrial species on the planet. An article on the New York times [3], suggests that jellyfish could even be as old as 700 million years, making them the oldest multi-organ animal on the planet!

White Jellyfish in an aquarium — Photo by Diego Guzmán on Unsplash

Practicing immortality

Isn't Immortality just a make-believe word? Surely, no biological life would be able to live forever, that’s insane…or is it? Well, perhaps for us humans, but for Turritopsis dohrnii[4], a species of jellyfish, this is a normal protocol when they are stressed or threatened. The jelly obtains this monumental feat through a process known as transdifferentiation, something that sounds too metaphysical to be true. But true it is, and it appears that this ‘immortal’ jellyfish is the only creature on the planet that can cheat death.

Their structure is intriguing

Even though we call them fish, jellyfish aren’t fish, they are cnidarians, along with sea anemones and hydra, which belong to the phylum cnidaria, a phylum consisting of more than 9000 species [5] mostly found in aquatic or marine ecosystems. Their gelatinous bodies are made up of a substance known as mesoglea [6], a kind of soft tissue that is made up of 90% water. But even without any well-defined organs but a basic nervous system, they exhibit some remarkable abilities, which makes them truly intriguing.

Some of them are as long as blue whales

Yes, you heard me; large species of jellyfish can even rival a blue whale in length. The lion’s mane jellyfish, which generally lives in the colder Arctic and Northern Atlantic waters, are known for their densely packed tentacles that resemble that of a lion’s mane. Although these jellies are not anywhere near the size of a blue whale in volume, their tentacles can grow to immense lengths. The largest lion’s mane jellyfish was reported to be 36.5 meters (120 feet) in length, which is longer than the largest recorded blue whale.

Most of the jellies glow

The vastness of the oceans could not be completely justified if one doesn’t talk about the true depths of the oceans. The deepest point in the ocean is so deep that Mount Everest could be completely submerged into it with ease. It was long thought that life could not simply exist in these dark and inhospitable depths. But deep ocean expeditions over the years have uncovered a truly breathtaking world out there.

Glowing jellyfish in an aquarium — Photo by Vino Li on Unsplash

In these conditions, most animals cannot see, unless they had some form of headlamps. And the harsher the conditions, smarter does nature get. Most animals that dwell here produce their own light, through a process known as bioluminescence. The jellies that live in the depths are also gifted with this glow. It is estimated that about 50% of jellyfish are bioluminescent.[7]Different creatures use this glow for different purposes, and even amongst different species of jellyfish, the glow could mean different things. Most of them are known to use bioluminescence as a defense mechanism to distract or startle a predator.

They are venomous, some are lethal

Encounters with jellyfish stings are pretty common across the beaches of the world. But there are few of them out there, which are so notoriously venomous, that you wouldn’t dare to visit the beach in their company. The Australian box jellyfish looks like gelatinous boxes, and are very attractive to gleam at, but hiding within their tentacles is a kind of venom so potent that it is considered to be the most venomous marine animal in the world! It is thought that the venom of the box jellyfish could kill a human in less than 5 minutes!