International Jellyfish Awareness Day

Let’s see a show of tentacles for all those who love jellyfish! ?? Every year, on November 3rd, we celebrate International Jellyfish Awareness Day—a day dedicated to appreciating these stunning, mysterious, and sometimes misunderstood ocean dwellers. Jellyfish are far more than their reputation for stinging swimmers. They boast ancient origins, possess unique adaptations, and can even glow in the dark! So, in honor of this special day, let’s dive deep into the mesmerizing world of jellyfish, uncover fascinating facts, and admire the incredible diversity of species floating through our oceans.

What Exactly Are Jellyfish?

Jellyfish are some of the oldest living creatures on the planet, with a lineage that dates back over 500 million years! These fascinating creatures are classified as cnidarians, a group that also includes sea anemones and corals. But what really makes jellyfish unique is their utterly bizarre anatomy. For one, they don’t have a brain, heart, or lungs. Instead, they rely on a simple nerve net to sense their surroundings, react to stimuli, and even find food. They’re essentially made up of 95% water, with their gelatinous bodies giving them that iconic, otherworldly appearance.

Jellyfish come in a variety of shapes, sizes, and colors. From the barely visible to those with tentacles stretching over 100 feet, they’ve adapted in incredible ways to thrive in the ocean. Despite their simple anatomy, jellyfish can exhibit complex behaviors—like bioluminescence (glowing in the dark) to confuse predators, or pulsing movements to navigate through the water.

Some interesting Jelly's

1. The Immortal Jellyfish – Turritopsis dohrnii

Meet Turritopsis dohrnii, also known as the "immortal jellyfish." Why immortal? This tiny jellyfish has an astonishing trick up its (metaphorical) sleeve: the ability to reverse its aging process. When faced with environmental stress, injury, or even old age, Turritopsis dohrnii can transform its cells back to a younger state, essentially becoming a juvenile jellyfish again. This process, called transdifferentiation, allows it to potentially live forever—at least in theory! While not all individuals survive every transformation, this unique adaptation makes the immortal jellyfish a true wonder of the animal kingdom.

2. The Blue Blubber – Catostylus mosaicus

Not all jellyfish sting! One of the friendlier species is the blue blubber jellyfish (Catostylus mosaicus), commonly found in Australia’s coastal waters, including the popular beaches of Sydney's Manly Beach. These non-stinging jellies are recognizable by their smooth, round bell, which comes in beautiful shades of blue, white, and even brown. While they don’t possess the toxic stingers typical of other jellyfish, their vibrant colors and gentle bobbing in the water make them a popular sight for swimmers and snorkelers. Unlike other jellyfish, the blue blubber doesn’t have long, trailing tentacles; instead, it has short, thick arms that it uses to capture plankton and other small organisms.

3. The Lion’s Mane Jellyfish – Cyanea capillata

If you thought jellyfish were small, think again! The Lion’s Mane jellyfish (Cyanea capillata) is the largest jellyfish species on Earth. With tentacles that can grow over 100 feet long—longer than a blue whale—this massive jellyfish is a real spectacle. It’s named for its thick, reddish-brown tentacles that resemble a lion’s mane. Found in the chilly waters of the Arctic, North Atlantic, and North Pacific, the Lion’s Mane jellyfish’s stings can be painful, though they’re rarely dangerous to humans. These jellyfish feed on small fish and zooplankton, using their long tentacles like a net to ensnare their prey.

Fun Facts and Myths About Jellyfish

Jellyfish have always captured people’s imaginations, but there are plenty of myths mixed in with the facts. Let’s clear up some of the most interesting bits of jellyfish lore!

• Jellyfish Glow in the Dark? Many jellyfish species can indeed glow, thanks to a phenomenon called bioluminescence. This ability helps them survive by either startling predators or attracting prey. The glow is produced by proteins that react with oxygen, creating a mesmerizing light in deep ocean waters. The crystal jellyfish (Aequorea victoria) is especially famous for this—its glow even led to the discovery of the green fluorescent protein (GFP) used in biological research today!
• Myth: All Jellyfish Sting Humans Not every jellyfish packs a sting that’s harmful to us. While some species have venomous stingers that can be dangerous (looking at you, box jellyfish!), others, like the blue blubber jellyfish or the harmless moon jellyfish (Aurelia aurita), have stings that are either too weak or completely non-threatening to humans. In fact, several species are safe enough for people to swim among!
• Jellyfish are Heartless and Brainless This one’s true! Jellyfish have no heart, brain, or central nervous system. Instead, their body is controlled by a nerve net, a simple set of nerves that help them respond to their environment. It may seem strange, but jellyfish don’t need complex organs to survive and thrive in the ocean.
• A Group of Jellyfish is Called a “Smack” Just like we have a “school” of fish or a “pod” of dolphins, a group of jellyfish is known as a smack! So, next time you see a bunch of jellyfish drifting together, you can impress your friends with that fun fact.

Jelly's do make for fantastic photography!

PS: We swam with many of the Jellyfish on the main photo in Nice, France. These do leave a bit of their stinging love behind, so watch out when swimming in the cote d'azur.