The moon jelly is a primitive animal which lacks respiratory, excretory, and circulatory systems. The adult medusa is transparent and looks much like an umbrella with tentacles. It has bright gonads that are under the stomach. There is a nerve net that is responsible for contractions in swimming muscles and feeding. Adults can have diameters up to 16 inches and are either male or female. Moon jellyfish are typically translucent white, but may take on a pink, purple, or orange hue depending on their last meal.
It is rare for moon jellies to live more than 6 months in the wild, though aquarium jellies may live for several years. They are eaten by a wide variety of predators including the Ocean Sunfish and the Leatherback Sea Turtle. Sea Birds may also prey on moon jellies. Polyps may live for up to 25 years.
Did you know?: The stings of moon jellies are not dangerous to humans. Jellyfish are not really fish, and many scientists are now referring to them as "jellies." A group of jellies is a smack. A large group of jellies is called a bloom. In 1991 over 2000 moon jellies were sent into space on the space shuttle Columbia to study the effects of weightlessness on their development.