Guidebook of Introduced Marine Species in Hawaii
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Species ListSpongesCnidariansPolychaetesMolluscsCrustaceansBryozoansAscidiansCollecting Specimens
Phyllorhiza punctata

Cassiopea andromeda

Pennaria disticha

Carijoa riisei

Diadumene lineata


Cassiopea andromeda Forskäl, 1775

Cassiopea andromedaUpside-down jellyfish

Phylum Cnidaria
Class Scyphozoa
Order Rhizostomeae
Family Cassiopeidae

This jellyfish usually lies mouth upward on the bottom, in calm shallow water, gently pulsating its bell to create water flow over it's arms. The bell of Cassiopea is yellow-brown with white or pale spots and streaks. The outstretched arms are also brownish with extended frilly tentacles. Adults can grow to 30 cm in diameter. They are often mistaken as sea anemones.
Cassiopea are typically found in shallow lagoons, intertidal sand or mud flats, and around mangroves. Cassiopea feed on drifting zooplankton. 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.
arm, bell and mouth of CassiopeaHawaiian Islands
Throughout main Hawaiian Islands.
Native Range
Present Distribution
Indo-Pacific and Hawaiian Islands
Mechanism of Introduction
Unintentional introduction, juvenile benthic stage in ships' hull-fouling or pelagic stage in ballast water.
A nuisance species, which can sting people. Ecological impact unstudied.
Like other jellyfish, Cassiopea has stinging cells or nematocysts in both its epidermis and gastrodermis, which is used for protection and capturing food. A sting from Cassiopea may result in skin welts, skin rash, itching, vomiting and skeletal pains depending on the individuals sensitivity to the toxin of the nematocysts.
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.
Pacific basin Cassiopea are currently placed in the one species C. andromeda (Hummelinck, 1968), but have been reported from Hawaii under two separate names, Cassiopea medusa Light 1914 and Cassiopea mertensii Brandt 1835. Cooke (1984) noted that these Cassiopea, with "their pseudobenthic habits are the most improbable adult immigrants." As C. medusa, Chu and Cutress (1954) note that it was "common the year round in bays and salt-water canals."
Cutress (1961) considered it to be introduced from the Philippines by ships as hull-fouling scyphistome to Pearl Harbor between 1941-1945. It was restricted to Pearl Harbor until about 1950, when it appeared in Honolulu Harbor and Ala Wai Canal. As C. mertensii Brandt, Uchida (1970) reported it from "the sandy bottom at a depth of 2 feet from Kaneohe Bay."
Under the name C. mertensii, it was previously known from only several locations in the South Pacific Ocean, especially the Caroline Islands. Cassiopea were seen in the early 1990s in fishponds on Molokai and in fishponds in Waikaloa area of the island of Hawaii .
Chu, G.W. and C.E. Cutress. 1954. Human dermatitis caused by marine organisms in Hawaii. Proc. Haw. Acad. Sci. 1953-54: 9.
Cooke, W.J. 1984. New scyphozoan records for Hawaii: Anomalorhiza shawi Light 1921 and Thysanostoma loriferum (Ehrenberg 1835); with notes on several other rhizostomes. Proc. Biol. Soc. Wash. 97: 583-588.
Cutress, C.E. 1961. [Comment on introduced jellyfish in Hawaii] p. 549, in: Doty, M.S. 1961. Acanthophora, a possible invader of the marine flora of Hawaii. Pac. Sci. 15(4): 547-552.
Hummelinck, P. W. 1968. Caribbean Scyphomedusae of the genus Cassiopea. Studies on the Fauna of Curacao and other Caribbean Islands. 25: 1-57.
Uchida, T. 1970. Occurrence of a rhizostome medusa, Cassiopea mertensii Brandt from the Hawaiian Islands. Annotat. Zool. Jap. 43:102-104.


© 2002 Hawaii Biological Survey, Bishop Museum