Cassiopea andromeda (Upside-down jellyfish)


Yellow to brown in color with white spots and/or streaks on the bell, brownish arms with frilly tentacles. It lies upside-down on the bottom, pulsating its bell.


Fairly common in the Indo-Pacific.


Throughout the Indo-Pacific and the Hawaiian islands. It is found in shallow lagoons or intertidal sand/mud flats, in a depth range of 1-15 meters.


Basic cnidarian reproduction involves an asexually reproducing polyp stage, alternating with a sexually reproducing medusoid stage, as described for Phyllorhiza punctata. This jellyfish is dioecious; an adult female jellyfish produces eggs and holds them until a male jellyfish releases sperm into the water. The female uses her arms and tentacles to gather sperm from the water to fertilize the eggs.


Up to 30cm. in diameter.

Prey / Predation

They feed on drifting zooplankton. A flow of water over its arms is created by pulsating its bell, lying upside-down. Individuals also harbors photosynthetic dinoflagellate algae that provides food to the jellyfish. The zooxanthellae live in the tissues on the ventral surface of the jellyfish, and the jellyfish sits on the bottom upside-down to provide sunlight to the symbiotic algae.

Special features

It can sting and cause irritation, skin rash, vomiting and pain. It was distributed by ballast water from ships.