Moon jellyfish vary in diameter between 10-16 inches. Their overall coloration is a translucent white but their tentacles are darker.

This species can easily be identified from others by the four yellowish-pink horseshoe shapes under their bell, which serve as their reproductive organs.

Moon jellyfish don’t have the usual organs we’re used to living creatures having such as a brain, heart, eyes, ears, etc. Essentially, this jellyfish is 95% water, a digestive system, and a mouth, with the ability to receive and expel oxygen through diffusion in their membrane rather than a set of lungs.

Their tentacles are only used for eating and do nothing for directional control. The moon jellyfish has just enough muscle control to stay near the water’s surface but otherwise uses currents to travel.

The moon jellyfish is a commonly studied jellyfish in the Aurelia genus. This species prefers water temperatures between 48–66 °F with differing mixtures of salt and fresh water; the most common location is the cooler waters and coasts surrounding Europe and North America.

Moon jellyfish feed on small organisms such as plankton, mollusks, fish eggs, larvae, and more. Their tentacles hang loosely at their sides until food makes contact and is stuck in the tentacle’s venomous mucus. The moon jellyfish has enough control to bring the tentacle to its gastrovascular cavity to digest the food.

Little is known about what particular vitamins and minerals the moon jellyfish needs but from the presence of certain digestive enzymes, we know they can process carbohydrates, lipids, and proteins.

Mating season for the moon jellyfish is in the summer time when groups, or “smacks”, of them gather together. Moon jellyfish will spend every day of this season attempting to reproduce, which can result in the death of a large amount due to expelling so much energy. Once a female has fertilized eggs, she will scatter larva on the sea floor. Those turn into polyps before budding into ephyrae, which become full adults.

Most species in this genus look identical and can only be distinguished through genetic sampling.