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Have you ever been mystified by the wonder of floating, translucent and boneless bodies? If you are, you’ve come to the right place! Sea jellies have long been a part of aquatic animal life at Shedd and have had a presence in the universe for over 400 million years. These illustrious creatures have a complex makeup that can be seen in all different shapes and sizes. The smallest jelly can be close to the size of a penny and the largest jelly is just as big as two bowling lanes. Keep reading to dive into their beauty and learn more about their venomous tentacles that protect them from prey, how they survive with no brain and what makes them such unique animals.

A pacific sea nettle pulses gently by, its vivid orange cap, soft and pulsing, trailing long thin red tentacles around its rim. Fluffy, semi-transparent ruffles of white tentacles billow from beneath its cap.

1. There are a variety of sea jellies species:

Currently, scientists have discovered nearly 2,000 jellies species, Shedd is home to 12.

Comb jellies are almost completely transparent and about the length of one's thumb, their body forming a bell shape ribbed in miniscule lines of fins.
Pacific sea nettles pulse hypnotically through their habitat, their long trailing tentacles brushing against one another.

2. Why do sea jellies look translucent?

Sea jellies are composed of a “jelly-like” substance, making them look squishy and soft. Why is this? Jellies are made up of about 90% water! This is what gives their bodies a “see through” look and sometimes, a nearly invisible look.

3. What is unique about their tentacles?

Not only do jellies defend themselves with their tentacles, but other animals also use their tentacles for protection. Some species of fish, especially very small fish, hang around jellies tentacles to take cover from any harm that may come to them.

The fine tentacles ringing a moon jelly's body, viewed up close.
A moon jelly, its bell-like body viewed from the side.

4. They don’t have hearts and they don’t need them!

Unlike many other animals, jellies do not have a heart nor a brain. Instead, they take in oxygen through their translucent bodies. This makes a heart unnecessary because they don’t need blood to carry their oxygen. Jellies also use their nerves to understand their surroundings, so a brain is not useful to them.

5. Can a sea jelly recover from a minor injury?

Sometimes! Jellies carry the incredible trait of being able to regenerate a part of their body when it gets injured. Not many animals are able to do this. If a jelly got cut in half, it would be able to turn into two jellies due to this regeneration process.

Now that you know some of the basics of sea jellies, you can impress your family and friends while experiencing them in-person at Shedd. If you want to learn more about various species of sea jellies at Shedd and where you can find them, head over to our jellies page!

—Bianca Diaz, Digital Marketing Intern