Moon Jellyfish

Moon Jellyfish is a type of jellyfish and they are well known for their strikingly beautiful appearance. They are mostly spotted in tropical ocean waters and have bioluminescent features that allow them to glow brightly in the dark. They are also known as saucer jellyfishes. It is not clearly known for how long the moon jellyfish has been present on this planet.

Moon Jellyfish Scientific Classification

  • Kingdom: Animalia
  • Phylum: Cnidaria
  • Class: Scyphozoa
  • Order: Semaeostomeae
  • Family: Ulmaridae
  • Genus: Aurelia
  • Species: A. aurita
  • Scientific Name: Aurelia aurita

Physical Description

Have a look at the distinct physical features of the moon jellyfishes.

Size: The size of the moon jellyfish varies between 25 cm and 40 cm or between 10 inches and 16 inches in diameter.

Sexual Dimorphism: There is no sexual dimorphism observed in moon jellyfishes and both sexes look completely alike.

Body: These jellyfishes have a translucent body and all their inner parts are visible from outside. The moon jellyfish has got four horseshoe-shaped gonads with a faint purple hue. The younger jellyfishes frequently have streaks and spots in them.


There are many known subspecies of the moon jellyfish. However, these jellyfishes look very similar to each other which mean that it is impossible to distinguish them without carrying out DNA examinations.


These creatures live for approximately a year in captivity as well as in the wild.

Distribution and Habitat

Moon jellyfishes are mostly spotted in the tropical waters in different parts of the world. Most of their populations can be seen in Indian Ocean, Pacific Ocean and the Atlantic coasts. Large populations of moon jellyfishes are found in Monterey Bay in the Californian coast and the open waters of East Coast, Gulf of Mexico, Europe and Japan



The moon jellyfish tend to move their bodies horizontally and they swim by vibrating the upper part of their bodies that have a bell-shaped structure. This upper part always remains close to water surface. In this way, they are able to spread their tentacles over a significantly larger area and this makes it easier for them to catch food. These jellyfishes can sometimes migrate and move from one spot to another in small groups to look for food.

A cluster of jellyfishes is called ‘smack’. When multiple smacks get together for creating a larger group, that group is referred to as a ‘bloom’. Typically one single bloom includes thousands of jellyfishes. The formation of the bloom rests on multiple factors, such as oxygen content of the water, the water temperature, ocean currents and the presence of nutrients in the water. The moon jellyfishes use their stings to capture their prey and inject the nematocysts in them that are present in the tentacles.


The moon jellyfishes stick to a carnivorous diet and feed mostly on planktons and organisms like tunicate, crustaceans, fish eggs, young polychaetes, mollusks, protozoans, rotifers, larvae, diatoms as well as other types of small jelly fishes.



The moon jellyfish is oviparous and breeds mostly during the months of summer and spring. The eggs reach their maturity in the gonads of the female moon jellyfish. The gonads are present in the pockets of the frills of oral arms at the lower part of their stomachs. Eggs are fertilized once the females ingest the floating sperm that is released by male moon jellyfishes.


Life Cycle

Once the eggs are fertilized, the female jellyfish releases them and they develop into larvae known as planula. Such newly-formed creatures tend to float and swim on water surface till they can find a solid and hard surface to effectively cling on to.

These larvae then turn into a polyp. The polyp divides under favorable conditions and this leads to the production of tiny individual jellyfishes. These small jellies are known as ephyra. Eventually the baby jellies grow into adults.


Check out the adaptations used by the moon jellyfish for their survival

  • They have a transparent body and this makes them not easily visible to their predators.
  • They have a radially symmetrical body and this makes it easier for them to look for food in all directions.
  • The moon jellyfish has got oral arms with tentacles. These tentacles are equipped with stinging cells known as ‘nematocysts’ that can be used for stunning their prey and ward off the predators.


They are often predated by other species of jellyfishes that are larger in size. Other creatures that pose a threat to the moon jellyfish include the leatherback turtle, ocean sunfish, swordfish, spadefish and tuna.

Conservation Status

The IUCN has listed the moon jellyfish under ‘Not Evaluated’ category.

Interesting Facts

Here are some interesting facts about the moon jellyfish.  

  • Their body lacks most of the systems and organs that are present in other creatures such as digestive systems, circulatory systems, respiratory systems, and even, brain, backbone, ears, blood, eyes and heart.
  • Moon jellyfish body is formed of 95% water, 1% mineral and 3% protein.
  • These creatures only have a single multi-purpose opening that is positioned between oral arms and this opening serves as anus, the mouth and the entry point for sperms in females.
  • They are related to the Portuguese man-of-war jellyfish.
  • This jellyfish is an edible species and it is considered to be a delicacy, particularly in some Asian countries.
  • The whitish and translucent moon-like circular bell of these creatures has earned them their name.   

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