And the answer: jellyfish.
You can find a smack of jellyfish in Australia’s Great Barrier Reef, a bloom of jellyfish at an aquarium, or a swarm of jellyfish on an episode of Spongebob Squarepants. Jellyfish might pre-date dinosaurs as they have existed for an estimated 65 million years. In addition to their invertebrate structure, they also lack a brain, and they’re 98% water.
Jellyfish can be found all over the world—from the deep ocean to shallow, coastal areas—and are some of the most diverse and unique creatures in the sea. Every jellyfish is boneless, brainless and bloodless, but what that means for individual species (and, not to mention, what it looks like) can be widely varied. There are thousands of different species of jellyfish (and two separate phyla), meaning the word “jellyfish” is more of an umbrella term than anything else.
Generally speaking, though, jellyfish are invertebrates, meaning they have no bones whatsoever. More specifically, they have no backbone, which makes them total pushovers (kidding, but they really don’t have backbones!). Jellyfish got their name from the jelly-like material of which they’re made, called mesoglea. So, no, jellyfish are not actually fish, and in fact many researchers today have swapped out the title for “sea jellies” instead.
Did you know?
Yesterday, November 3rd, was World Jellyfish Day! Scientists have long believed that jellies have lived on the planet for millions of years, and that theory was proved right with the 2007 discovery of perfectly preserved 505-million-year-old jellyfish fossils in Utah. Today, jellies continue to thrive almost all over the world because they need very little oxygen, enjoy a broad diet, reproduce very quickly, and shrink when food reserves dwindle, only to revive themselves when food is available again (I’d like to shrink myself down next time I get hangry…)
Learn more about jellyfish here.