The most common jellyfish beachgoers see, the moon jelly has a transparent, milky white bell rimmed with hundreds of short, hair-like tentacles. Its four oral arms, frilled along one edge, hang from the center of the bell. In young moon jellies, the gonads are white, but in mature animals the gonads are tinged with color.
Moon jellies range from the Arctic to Florida and Mexico and from Alaska to southern California.
Their sting, toxic but mild, produces a hot rash and burning sensation. It expands then quickly contracts its bell, an action that forces water away from the bell and pushes the animal in the opposite direction. The moon jelly is the easiest of the true jellies to raise in captivity, and its remarkable life cycle which goes through five stages has been widely studied. Like all true jellyfish, the moon jelly is dimorphic, meaning that it has two distinct body shapes during its life cycle, and exhibits alternation of generations, meaning that it reproduces both sexually and asexually. The jellyfish exhibit at the Aquarium features the life cycle of the moon jelly .