The Lion’s Mane Jellyfish Is Huge and Looks Out of This World

Before we take a deep dive on the very big jellyfish, it’s important to understand a bit about jellyfish overall. They are part of the phylum Cnidaria, which also includes sea anemones, sea whips, and corals. Jellyfish are very old animals, part of a group scientists call medusozoa, that have been floating around the seas for at least 500 million years. That’s pretty impressive for creatures that have no brains, blood, hearts, and are about 95% water.

Jellyfish are simple critters that have three layers. This includes the outer layer called the epidermis; a middle layer made of a thick, elastic, jelly-like substance known as mesoglea; and the inner layer, or the gastrodermis. Although jellyfish don’t have brains, they do have nerve nets, which are very important for them. The nerve nets allow jellyfish to sense changes in water chemistry that indicate there’s food or that another animal is touching them, know whether they are facing up or down, and detect light.

When it comes to eating, jellyfish have a simple digestive cavity. It acts as both a stomach and intestine, and the creatures have an opening that works as both a mouth and a butt. Laugh all you want, but jellyfish shouldn’t be messed: They have tentacles with special cells that release venom to capture prey or respond to enemies.

Jellyfish also have the rare distinction of going to space. In the 1990s, NASA launched thousands of jellyfish into orbit for experiments on Spacelab (not to be confused with the ill-fated Skylab) to see how microgravity would affect them. Thousands of jellies were born in space. Long story short: The space jellyfish did not have a good time when they came back to Earth and were unable to cope with gravity.