Rising and sinking serenely like the bubbles of a lava lamp, jellyfish are some of the most enigmatic creatures of our oceans. So much is unknown about these bizarre animals, and there are countless theories about everything from their evolution to their (im)mortality. To help you understand a little more about them, we bring you some seemingly far-out facts about their existence, biology and behaviour.

They are mostly water

Jellyfish are made of 95 percent water and five percent solid matter. The solid matter is composed of three layers: the epidermis is the outer layer, the mesoglea (or jelly) is the middle layer, and the gastrodermis is the inner layer.

They are pretty ancient

Though jellies are soft-bodied and lack a skeleton, making fossils rare, there is evidence that jellyfish predate dinosaurs by some 400 million years.

They’ve been involved in groundbreaking scientific research

A historic moment for jellyfish came in May 1991, when 2,478 moon jelly polyps and babies were launched into space aboard the Space Shuttle Columbia. Biologist Dorothy Spangenberg of the Eastern Virginia Medical School wanted to learn about how weightlessness affected the development of juvenile jellies. She monitored calcium loss in the creatures, which by extension was designed to further scientists’ understanding of similar losses in humans in space.


Some die young, others may live forever © NOAA Public Domain

Some die young, others may live forever

Most jellyfish live anywhere from a few hours to a few months. But a species of jelly called Turritopsis nutricula may be immortal. The jelly is purportedly able to play its life cycle in reverse, transforming from an adult medusa back to an immature polyp.

They’re as spineless as a politician

The creatures lack not only bones, but heads, hearts and brains.

…but can sniff out prey

Researchers from the Monterey Bay Aquarium Research Institute surmise that cross jellies (Mitrocoma cellularia), common to Monterey Bay in the spring and summer, can “smell” prey through chemicals in the water.

…and eye up feeding sites

A recent study found that the box jellyfish, Tripedalia cystophora, has 24 eyes that always point up. The jellyfish looks through the water surface for tree branches. This way, it can swim towards mangrove swamps to feed.

They are a boon to cancer research

Green fluorescent proteins (GFPs) from the Aequorea victoria jellyfish species have transformed biomedical research. The glow-in-the-dark proteins can illuminate specific proteins within the human body to track microscopic activity, such as cancer growth. 

Mayo Clinic scientists recently inserted a version of GFP and a gene from a rhesus macaque known to block a virus that causes feline AIDS into a cat’s unfertilised eggs. When the kittens were born, they glowed green in ultraviolet light, indicating that the gene was successfully transferred. Biologist Osamu Shimomura won a Nobel Prize in Chemistry in 2008 for discovering GFP.


They never lose their sting

Jellyfish can sting even when they are dead. In 2010, around 150 swimmers at Wallis Sands State Park in New Hampshire were stung by the floating, 40-pound carcass of a lion’s mane jellyfish.

They offer two-for-one

Jellyfish are dioecious; that is, they are either male or female. In most cases, to reproduce, both males and females release sperm and eggs into the surrounding water, where the (unprotected) eggs are fertilised and mature into new organisms.

They can grow extremely long

The lion’s mane jellyfish is the largest known species of jellyfish. The Arctic lion’s mane jellyfish is one of the longest known animals and the largest recorded specimen had a bell (body) with a diameter of 2.3 metres and the tentacles reached 36.5 metres. It was found washed up on the shore of Massachusetts Bay in 1870.

They can clone themselves

If a jellyfish is cut in two, the pieces of the jellyfish can regenerate and create two new organisms. Similarly, if a jellyfish is injured, it may clone itself and potentially produce hundreds of offspring.