Aurelia (cnidarian)

Aurelia is a group of jellyfish often called moon jellies.

They belong to a class called Scyphozoa. There are 25 accepted species in this group today. Many other types might still be waiting to be named. These jellies live in many of the world's oceans. You can find them in the Atlantic, Arctic, Pacific, and Indian Oceans. They often live in temperate waters near places like Japan, Korea, and the United States.

Moon jellies have a very unique way of working. They do not have hearts, lungs, or blood to move things. Instead, they breathe by letting oxygen pass through their thin skin. They use tiny hairs to move water through their bodies. This helps them get the oxygen and food they need. Their bodies are mostly clear and see-through. However, their color can change based on what they eat. If they eat certain tiny creatures, they might look pink or lavender. If they eat brine shrimp, they may look orange.

Scientists have studied these jellies for a long time. A man named Jean-Baptiste Lamarck first described the genus in 1816. He wrote about them in his book, Histoire Naturelle des Animaux sans Vertèbres. For a long time, people mostly studied the species Aurelia aurita. They also looked at Aurelia labiata and Aurelia limbata during the 1900s. In the early 2000s, scientists used genetic data to learn more. They found that there is more variety in these jellies than they first thought. This makes it hard to tell some species apart just by looking.

The life of a moon jelly has many steps. It starts as a tiny larva called a planula. This larva settles on the sea floor to become a polyp. These polyps then grow into small, swimming jellyfish called ephyrae. Finally, they grow into the large, adult medusae we see swimming. Most adult jellies have four bright gonads under their stomachs. Some jellies might even have more than four. In the wild, they usually live for only a few months.

Moon jellies are an important part of the ocean food web. Many animals like to eat them. The ocean sunfish and leatherback sea turtles both eat moon jellies. Even some sea birds will eat them when they are near the surface. While they are being eaten, they also eat tiny creatures called zooplankton. Sometimes, large groups of jellies can even clog fishing nets. This can make it a hard job for people who fish in the ocean. They are a fascinating part of our blue planet.