Moon Jellyfish Facts

The moon jellyfish (Aurelia aurita) is a common jelly that is easily recognized by its four horseshoe-shaped gonads, which are visible through the top of its translucent bell. The species gets its common name for the way its pale bell resembles a full moon. Fast Facts: Moon Jellyfish Scientific Name: Aurelia auritaCommon Names: Moon jellyfish, moon jelly, common jellyfish, saucer jellyBasic Animal Group: InvertebrateSize: 10-16 inchesLifespan: 6 months as an adultDiet: CarnivoreHabitat: Tropical and subtropical oceansPopulation: AbundantConservation Status: Not Evaluated Description The moon jellyfish has a translucent 10 to 16 inch bell with a fringe of short tentacles. The tentacles are lined with nematocysts (stinging cells). Most moon jellies have four horseshoe-shaped gonads (reproductive organs), but a few have three or five. The bell and gonads may be translucent white, pink, blue, or purple, depending on the animals diet. The jellyfish has four fringed oral arms that are longer than its tentacles. Habitat and Range The species lives in tropical and subtropical oceans worldwide. It is common along the Atlantic coast of North America and Europe. Moon jellyfish frequent coastal and epipelagic areas (top layer of the ocean) and can survive the lower salinity of estuaries and bays. Diet and Behavior The moon jellyfish is a carnivore that feeds on zooplankton, including protozoa, diatoms, eggs, crustaceans, mollusks, and worms. The jelly is not a strong swimmer, mainly using its short tentacles to stay near the water surface. Plankton get trapped in the mucus coating the animal and passed via cilia into its oral cavity for digestion. Moon jellyfish absorb their own tissue and shrink if they are starved. They grow to their normal size when food becomes available. Although water currents group jellyfish together, they live solitary lives. Scientists believe jellyfish may communicate with one another using chemicals released into the water. The jellyfish life cycle includes both sexual and asexual phases. Dorling Kindersley / Getty Images Reproduction and Offspring The jellyfish life cycle has a sexual and asexual component. Each adult (called a medusa) is either male or female. In the open ocean, jellyfish release sperm and eggs into the water. Fertilized eggs develop and grow in the water as planula for a few days before attaching to the sea floor and growing into polyps. The polyp resembles an upside down medusa. Polyps asexually bud off clones that develop into mature medusae. In the wild, Aurelia jellyfish reproduce for several months. Near the end of summer, they become susceptible to disease and tissue damage from the exertion of reproduction and diminishing food supplies. Most moon jellyfish probably live about six months, although captive specimens may live many years. Like the immortal jellyfish (Turritopsis dohrnii), the moon jellyfish can undergo lifecycle reversal, essentially growing younger rather than older. Conservation Status The IUCN has not evaluated the moon jelly for a conservation status. The jellyfish are abundant, with adult populations spiking or blooming in July and August. The moon jellyfish thrives in water containing a lower than normal concentration of dissolved oxygen. Dissolved oxygen drops in response to increased temperature or pollution. Jellyfish predators (leatherback turtles and ocean sunfish) cannot tolerate the same conditions, are subject to overfishing and climate change, and may die when they mistakenly eat floating plastic bags that resemble jellies.Thus, jellyfish numbers are expected to grow. Moon jellyfish blooms in summer have environmental causes and consequences. Michael Nolan / Getty Images Moon Jellyfish and Humans Moon jellyfish are consumed as food, especially in China. The species is of concern because an overabundance of the jellies significantly decreases plankton levels. People frequently encounter moon jellyfish because of their abundance and preference for coastal waters. These jellyfish do sting, but their venom is mild and considered harmless. Any clinging tentacles may be rinsed off with salt water. The venom may then be deactivated with heat, vinegar, or baking soda. Sources Arai, M. N. A Functional Biology of Scyphozoa. London: Chapman and Hall. pp. 68–206, 1997. ISBN 978-0-412-45110-2.He, J.; Zheng, L.; Zhang, W.; Lin, Y. Life Cycle Reversal in Aurelia sp.1 (Cnidaria, Scyphozoa). PLoS ONE. 10 (12): e0145314, 2015. doi:10.1371/journal.pone.0145314Hernroth, L. and F. Grondahl. On the Biology of Aurelia Aurita. Ophelia. 22(2):189-199, 1983.Shoji, J.; Yamashita, R.; Tanaka, M. Effect of low dissolved oxygen concentrations on behavior and predation rates on fish larvae by moon jellyfish Aurelia aurita and by a juvenile piscivore, Spanish mackerel Scomberomorus niphonius. Marine Biology. 147 (4): 863–868, 2005. doi:10.1007/s00227-005-1579-8Solomon, E. P.; Berg, L. R.; Martin, W. W. Biology (6th ed.). London: Brooks/Cole. pp. 602–608, 2002. ISBN 978-0-534-39175-1.