Aurelia (cnidarian)

Moon jellies are clear sea animals.

They live in many big oceans. They have hundreds of short arms. These arms do not sting much.

These animals do not have lungs. They take in air from the water. Their color can change too. They may look pink if they eat certain small creatures.

They can be eaten by sea turtles. It is fun to watch them swim!

Moon jellies are a group of jellyfish called Aurelia.

They live in many big oceans. You can find them in the Atlantic, Pacific, and Indian Oceans. They like water that is not too hot or too cold.

These animals have a clear body. They do not have lungs or hearts. Instead, they take in oxygen from the water through their thin skin. They use tiny hairs to move water through their bodies. This helps them get the oxygen they need. Their color can change based on what they eat. If they eat certain small creatures, they might look pink or orange.

Moon jellies have a very interesting life. They start as tiny larvae called planulae. These larvae settle on the sea floor and become polyps. These polyps then grow into young jellyfish called ephyrae. Finally, they become the adult medusae we see swimming.

Most moon jellies live for only a few months in the wild. Many animals like sea turtles eat them for food.

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.

Aurelia is a genus of jellyfish commonly known as moon jellies.

These gelatinous zooplankton belong to the class Scyphozoa. They are found in the Atlantic, Arctic, Pacific, and Indian Oceans. Most species prefer temperate regions with consistent currents. You can find them in waters near northern China, Japan, Korea, and New Zealand. They also live along the coasts of the United States and northern Europe.

The anatomy of an Aurelia medusa is quite specialized. They lack respiratory, excretory, and circulatory systems. Instead, they breathe through diffusion. This happens when oxygen passes from the water through their thin body membrane. Their large surface area to volume ratio makes this diffusion efficient. To help, they use ciliated action to move water through a gastrovascular cavity. This movement brings in oxygenated water and expels low-oxygen water.

Feeding and digestion also rely on specific body parts. Moon jellies differ from many other jellyfish because they lack long, potent stinging tentacles. Instead, they have hundreds of short, fine tentacles along the bell margin. They use these tentacles, which are laden with nematocysts, to catch zooplankton. The food is tied with mucus and brought to the gastrovascular cavity. A muscular manubrium helps food travel, while radial canals disperse it. Inside, digestive enzymes from serous cells break down carbohydrates, proteins, and lipids.

The life cycle of Aurelia involves an alternation of generations. It begins with a tiny, ciliated larva called a planula. This larva settles on the sea floor and becomes a polyp known as a scyphistoma. These polyps reproduce asexually through a process called strobilation. This process buds off small, swimming jellyfish called ephyrae. The ephyrae eventually grow into the large, sexually reproducing medusa stage. In some species, like Aurelia coerulea, polyps can form directly from juvenile medusae.

Scientists have spent a long time studying these organisms. Jean-Baptiste Lamarck first described the genus in 1816. For much of the 20th century, researchers focused on Aurelia aurita, Aurelia labiata, and Aurelia limbata. However, genetic studies in the early 2000s changed our understanding. They revealed that diversity is much higher than physical appearance suggests. This means many species are "cryptic," meaning they look almost identical but are genetically different.

Moon jellies play a significant role in marine ecosystems. They are a vital source of nutrients for many predators. The ocean sunfish, leatherback sea turtles, and even some sea birds eat them. In the Seto Inland Sea, large aggregations of 250 individuals consumed nearly 100% of the mesozooplankton biomass during July and August. They also show a unique tolerance for hypoxia, which is low dissolved oxygen. While other fish predators struggle in low oxygen, moon jellies thrive. This allows them to face less competition for food in certain coastal waters.

Despite their importance, moon jellies can impact human activities. Large groups can clog and damage fishing nets used by trawling boats. This can force fishermen to relocate their operations. Interestingly, a 2020 study showed that their bodies are not significantly harmed by microbeads. They were able to recognize that these artificial materials were not food. This suggests they can distinguish between nutrients and human-made waste.