When I tell people my favorite animal are jellyfish, I get the most interesting reactions – a weird look, a raised eyebrow, or a full-on side-eye. But let me convince you that I am totally right about this.
These strange creatures with no brain, no heart, no bones, and no lungs have been drifting through our oceans for around 500 million years. Yes, they’re older than dinosaurs! So how come an animal made of 95% water has survived this long, while the mighty T. Rex didn’t? Well, I’m glad you asked, because I’ve got the answers!
Wild science of jellyfish you’ve never heard before
Think it’s hard to kill a lion? Try killing a jellyfish. They might look fragile, but some of them can quite literally turn back time! When the adult jellyfish (called a medusa) is physically damaged or experiences stresses it can reverse age – shrinking, reabsorbing their tentacles reverting back to a baby-like stage called a polyp. It can then start to grow up again, starting life from scratch again. Imagine that!
And that’s just the beginning. Roughly half of all jellyfish glow in the dark thanks to bioluminescent – which was, by the way, the inspiration for LED technology. They’re not technically fish at all and more related to plankton and corals. The largest jellyfish reaches over 7 feet wide with tentacles stretching 121 feet – that is longer than a blue whale. Ever seen those tons of jellyfish drifted up to shore and accidentally stepped on one? It stings like hell. That’s because the tentacles still contain venom, even after death.
jellyfish: born survivors
Jellyfish aren’t just cool and fascinating – they’re also a little terrifying. That’s not because their tentacles sting you, when you touch them – although that can be painful as well – but because they’re becoming a real environmental problem and a warning sign for climate change. As ocean temperatures rises, jellyfish populations are exploding. Warm water seems pretty nice – finally a swim without freezing! – but it’s bad news for most marine life. Jellyfish love warm water – just like us – because it amps up their metabolism but a lot of the other sea life is not really a fan. Fish, for example, find it much harder to extract oxygen from warmer water since it holds less dissolved oxygen. That’s not only bad for the sushi roll on my plate that won’t have any fish in there anymore. Fish are vital for the marine life. They’re part of a long food chain and also help corals thrive, which is important because corals are needed as a food resource, coastal protection and shelter. Jellyfish are not as supportive and don’t help corals, so having more of them and less of fish is not great; it makes the balance of the entire ecosystem collapse.
Jellyfish have perfected the art of survival to a degree far surpassing that of most other types of living things.
~ Lisa-Ann Gershwin
Jellyfish and their dynamic food chain
Another factor that is incredibly fascinating and what makes them such a cool invertebrate is that they switch between food chains! We are part of the high-energy food chain, just like sharks, whales, and fish. Jellyfish are considered to be the top predators of the low-energy food chain, where all the plankton falls under. But here’s the twist – they also eat eggs and larvae of fish. So they eat the plankton that is needed for those larvae to grow, but they also eat the larvae themselves. They switch between food chains!
When jellyfish consume so many fish eggs and larvae, it prevents new fish populations from forming – disrupting the whole foundation of the food chain. Once a region becomes dominated by jellyfish, it’s extremely difficult to reverse. They’re incredibly resilient, reproducing both sexually and asexually, and survive in conditions where most marine live can’t.
So yes – they might look like undefined transparent little blobs floating around while you’re trying to go for a casual swim, but jellyfish are ancient survivors, climate indicators and ecosystem shifters. For an animal with no brain they hold a lot of power. Maybe next time you see one drifting through the ocean, you’ll look twice – because these mindless creatures might outlive us all.
If that made you even a little bit curious, check out Jellyfishing for Answers – Future Ecologies – Apple Podcasts to dive deeper into their world.