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With their translucent white bells—which can reach 12 inches in diameter—it’s not difficult to see where moon jellies get their name. Their bells are luminous with a blue-grey transparent disk in the center and glowing, horseshoe-shaped organs. Short, delicate, fringe-like tentacles hang from their bell margins. These tentacles deliver a very mild sting.
A Note From the Caretaker
Moon jellies are one of the most prolific species at the National Aquarium. We can control when they reproduce by manually adjusting temperatures in their habitat.
Learn more about moon jellies! Did you know that when food is limited, moon jellies can shrink to one-tenth of their size to save energy? They return to their previous size when more food becomes available.
This species is found in temperate and tropical waters worldwide, and near the surface of shallow bays and harbors. During the summer, moon jellies are commonly found in the lower Chesapeake Bay.
As moon jellies pulse and drift, they feed on zooplankton like tiny shrimp and other crustaceans.
The bell of a moon jelly can be up to 12 inches wide, about the size of a dinner plate.
Jellies can survive in waters with lower oxygen levels and higher nutrient loads than many fish species, and many of their predators—like endangered sea turtles—are becoming scarcer. The lack of predators can lead to large jelly blooms, giving the impression that jellies are taking over and hinting that—as our exhibit name suggests—the ocean is out of balance.
Sea turtles and other jelly-eating animals such as tuna, sunfish, butterfish and spiny dogfish help keep the jelly populations in balance. All seven species of sea turtles include them in their diets. The largest sea turtle species, the leatherback, depends on jellies entirely for food. Because jellies are more than 90% water and an adult leatherback can weigh more than 2,000 pounds, one turtle can consume a lot of jellies.