Moon Jellyfish

Kingdom:      Animalia
Phylum:         Cnidaria
Class:            Scyphozoa
Order:           Semaeostomeae
Family:          Ulmaridae
Genus:           Aurelia
Species:         Aureliaaurita

The moon jellyfish, Aureliaaurita, is known under several different common names, including moon jelly, saucer jellyfish and common jellyfish. It belongs to a group of very similar species of jellyfish in the genus Aurelia and it is virtually impossible to distinguish these species from each other without testing their genetic material. The name moon jellyfish is therefore frequently used for all these species, not just Aureliaaurita. In most cases, the information found below in this article is not only true for Aureliaaurita but for all its close relatives as well.

Moon jellyfish distribution and habitat

Members of the genus Aurelia can be found in most of the world's oceans and can be encountered as far north as 70° latitude and as far south as 40°. Moon jellyfish is typically found close to shore, including harbours and estuaries. Its preferred temperature is 9 °C to 19 °C, but it can be found in freezing cold waters as well and in tropical regions where the temperature exceeds 30°C. When it comes to salinity the moon jellyfish is normally found in parts of the ocean where the salinity exceeds 23 ppt, but specimens have actually been reported from waters where the salinity is no more than 3 ppt.

Anatomy and appearance

The adult medusa is translucent and typically attains a size of 25-40 cm across. It is transparent with four bright gonads shaped like horseshoes under the stomach. Feeding and swimming is directed by a nerve inside the jellyfish, but this animal is only capable of limited motion; most of the time it just drifts around in the ocean.  The bottom of the medusa is fitted with tentacles which are used for catching prey. The food ends up in the gastrodervascular cavity (stomach), which has both gastrodermis and epidermis. The moon jellyfish doesn’t have any respiratory organs, e.g. lungs, trachea or gills. It breathes by diffusing oxygen from the surrounding water through its thin membranes. Well oxygenated water enters the gastrovascular cavity and low oxygenated water is expelled.

Moon jellyfish Feeding

The moon jellyfish (both medusa and larva) kills its prey by stinging it with the nematocysts found on its long tentacles. Prey items include organisms such as crustaceans, protozoans, diatoms, molluscs, rotifers, tunicate larvae, polychaetes, other small medusas, and eggs from animals like fish.

Moon jellyfish predators

A lot of predators like to eat moon jellyfish, including certain birds, fish, and sea turtles. The Leatherback Sea Turtle (Dermochelys coriacea) and the Ocean Sunfish (Mola mola) are just two examples of predators known to feed on this jellyfish. Humans also like to eat moon jellyfish, especially in South-East Asia.

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