Size: Up to 18 inches (46 cm) in diameter.
Range: In Atlantic Ocean from the Arctic to Mexico. In Pacific Ocean, from Alaska to southern California.
Jellyfish are sort of like floating mushrooms, with long thread-like arms reaching underwater like weeping willow branches. They might seem to melt away on the beach, but they're not that fragile. They survive long sea journeys and much wave battering. Jellyfish get around in the ocean by means of a pulsating action. Long ago, people called jellyfish "sea lungs" because their rhythmic movement through the water resembles how our chests move as we breathe.
The moon jellyfish is one of the most abundant jellyfish in the Mid-Atlantic region. Its disc, or umbrella, may be as large as 18 inches across and gives the animal the appearance of a flying saucer. The umbrella is divided into eight equal parts, each of which has many small tentacles that contain stinging cells to help the jellyfish get food and defend itself. These stinging cells are like tiny harpoons and are triggered when the tentacle is touched. So be careful - even a dead jellyfish can sting. While the sting of the moon jellyfish may be irritating, species such as the Portuguese Man-of-War may inflict much more serious, even deadly, stings.
Looking at the moon jellyfish from directly above or below, you can see four purple horseshoe-shaped parts. These are the gonads, or primary sex glands. In August or September, the moon jellyfish's arms have a distinct pink color because of the large number of developing larvae on the edge of the umbrella.
To learn more about jellyfish, check out the Jellyfish bulletin in our Sea Grant publications catalog.