Description: Ninety-five percent or more of the weight of the Moon jellyfish is water; it has no brain, eyes or heart. The whitish color of its bell or moon-shaped dome often shows shades of blue, pink or purple – color believed to depend on its diet. The four horseshoe-shaped reproductive organs can be seen in the middle of its dome. Fringe-like tentacles are around the dome. The tentacles are lined with stinging cells (nematocysts) that can be used to sting prey. The jellyfish is also coated with a sticky mucous that collects prey. The feeding tube is short and stout, with four long oral arms with frilly margins around the mouth. They move about and stay at the top by pulsations of the bell.

Size: The Moon jellyfish ranges between 2-15 inches (5-38 cm) in diameter, with average diameter being about seven inches (17.8 cm) and three inches (7.6 cm) tall.

Behavior: Moon jellyfish tend to live alone but water currents and wind may tend to steer them in groups called blooms. They swim horizontally with their bell facing the surface of the water. As they swim, they spread their tentacles, making it easier for food to be caught. They also defend themselves by stinging with their tentacles. Special muscles called coronal muscles on the bottom side of the bell, allow the animal to pulsate in order to move. There is a nerve network that is responsible for contractions in swimming muscles and feeding responses. As the oxygen rate in the water goes down, so too does the respiratory rate of the jellyfish.

Diet: The Moon jellyfish is carnivorous and feeds primarily on zooplankton.

Senses: Moon jellyfish can smell, taste, sense both dark and light, up and down, and can remain balanced in the water.

Communication: Some species of jellyfish are known to communicate with others of their kind by means of chemicals. If communication exists between Moon jellyfish, it is likely by the same method.

Reproduction: Male Moon jellyfish release sperm that are taken internally by the female for fertilization. The eggs then develop in pockets or grooves on the arms of the female until ready to be released.

Habitat/range: Moon jellyfish can be found in temperate waters, often near coast lines throughout the world.

Status: Not evaluated by IUCN.