''Cassiopea'' (upside-down jellyfish) is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

true jellyfish The Scyphozoa are an exclusively marine class of the phylum Cnidaria, referred to as the true jellyfish (or "true jellies"). The class name Scyphozoa comes from the Greek word ''skyphos'' (), denoting a kind of drinking cup and alluding to the ...

and the only members of the family Cassiopeidae. They are found in warmer coastal regions around the world, including shallow

mangrove A mangrove is a shrub or tree that grows in coastal saline or brackish water. The term is also used for tropical coastal vegetation consisting of such species. Mangroves are taxonomically diverse, as a result of convergent evolution in severa ...

swamps, mudflats, canals, and turtle grass flats in

Florida Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and to ...

, and the Caribbean and

Micronesia Micronesia (, ) is a subregion of Oceania, consisting of about 2,000 small islands in the western Pacific Ocean. It has a close shared cultural history with three other island regions: the Philippines to the west, Polynesia to the east, and ...

. The

medusa In Greek mythology, Medusa (; Ancient Greek: Μέδουσα "guardian, protectress"), also called Gorgo, was one of the three monstrous Gorgons, generally described as winged human females with living venomous snakes in place of hair. Those ...

usually lives upside-down on the bottom, which has earned them the common name. These jellyfish partake in a symbiotic relationship with photosynthetic dinoflagellates and therefore, must lie upside-down in areas with sufficient light penetration to fuel their energy source. Where found, there may be numerous individuals with varying shades of white, blue, green and brown.

Species

According to the ''

World Register of Marine Species The World Register of Marine Species (WoRMS) is a taxonomic database that aims to provide an authoritative and comprehensive list of names of marine organisms. Content The content of the registry is edited and maintained by scientific specialis ...

'', this genus includes 8 species: * '' Cassiopea andromeda'' (Forsskål, 1775) * '' Cassiopea depressa'' Haeckel, 1880 * '' Cassiopea frondosa'' (Pallas, 1774) * '' Cassiopea maremetens'' Gershwin, Zeidler & Davie, 2010 * '' Cassiopea medusa'' Light, 1914 * '' Cassiopea mertensi'' Brandt, 1838 * '' Cassiopea ndrosia'' Agassiz & Mayer, 1899 * '' Cassiopea ornata'' Haeckel, 1880 Also recognized: * '' Cassiopea xamachana'' Bigelow, 1892

Defense system

''Cassiopea'' species have a mild sting since they are primarily photosynthetic, but sensitive individuals may have a stronger reaction. The photosynthesis occurs because, like most

coral Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and ...

s, they host

zooxanthellae Zooxanthellae is a colloquial term for single-celled dinoflagellates that are able to live in symbiosis with diverse marine invertebrates including demosponges, corals, jellyfish, and nudibranchs. Most known zooxanthellae are in the genus ''S ...

in their tissues. The stinging cells are also found in cellular masses, dubbed "cassiosomes", excreted in a

mucus Mucus ( ) is a slippery aqueous secretion produced by, and covering, mucous membranes. It is typically produced from cells found in mucous glands, although it may also originate from mixed glands, which contain both serous and mucous cells. It ...

; people swimming near the jellyfish may come in contact with these cassiosomes and be stung. The stings, appearing in the form of a red rash-like skin irritation, are known for being extraordinarily itchy. Sometimes this jellyfish is picked up by the crab '' Dorippe frascone'' and carried on its back. The crab uses the jellyfish to defend itself against possible predators.

Behavior

Certain species of ''Cassiopea'' have been observed to enter a sleep state - exhibiting decreased pulsation rate, reduced responsiveness to stimuli, and compensatory rebound sleep after deprivation.

References

External links

Photo of a Crab carrying an Upside Down Jellyfish (Cassiopea andromeda)

{{Taxonbar, from=Q289354 Cassiopeidae