Cassiopea xamachana

Geographic Range

The northern distribution limit of Cassiopea xamachana is the southeastern tip of the United States as upside-down jellyfish appear in large numbers in varying areas of the Florida Keys. This species is also found in Bermuda, the Caribbean Sea and warmer areas of the western Atlantic Ocean. They are commonly found in places such Walsingham Pond and Harrington Sound, on the bottom of an inshore bay or pond. The highest density of these scyphozoans occurs in the Caribbean but throughout the course of the last decade the distribution seems to be expanding to other locations such as the Hawaiian and Mediterranean waters, including the Red Sea. (Hofmann, et al., 1996; Kitt and Costley, 1998)


Cassiopea xamachana frequently resides inshore in shallow, tropical, marine waters, on particular sandy mudflats. Upside-down jellyfish most commonly use muddy substrata in mangrove leaves to settle upon, giving rise to the common name "mangrove jellyfish." The jellyfish are found during the mid to late summer with very few scyphistomae observed between late November and early June. Numerous quantities of the benthic-dwelling ephyra and strobilating scyphistomae were observed from late June until the end of the fall season. There were nearly none observed throughout the winter or spring. (Berryman, 2005; Hofmann, et al., 1996; Kitt and Costley, 1998; Niggl and Wild, 2009)

  • Range depth
    Shallow Areas (low) m
    (low) ft

Physical Description

The up-side down jellyfish does not have the typical physical characteristics of jellyfish. Often it has a somewhat green or gray/blue coloration. This display is the result of numerous densely packed symbiotic zooxanthellae, Symbiodinium microadriaticum. The medusa, the dominant adult phase of the life cycle, possesses four branching tentacles that extend from the body, up into the water column. These structures are used in feeding and provide nutrients in combination with what is made available by the photosynthetic dinoflagellates. The large, dome shaped exumbrella of the medusa contains a central depression that is used mainly for attachment purposes as the up-side down jellyfish remains sedentary throughout a majority of its lifecycle. (Berryman, 2005; Hofmann, et al., 1996)

  • Range length
    20.3 to 35.6 cm
    7.99 to 14.02 in
  • Average length
    30.5 cm
    12.01 in
  • Range basal metabolic rate
    1.3 to 4.87 cm3.O2/g/hr
  • Average basal metabolic rate
    2.39 cm3.O2/g/hr


Cassiopea xamachana is dioecious, with each sex contributing one type of gamete (sperm or eggs) that will combine to form a zygote. The developing embryos are covered in specialized mucus and wrapped around the bases of sex specific vesicles. This brooding will continue until cilliated planula emerge and begin to swim, commonly characterized as searching behavior. Eventually, the larva will settle on a suitable substrate and irreversibly attach, beginning the metamorphosis into the sedentary polyp stage of the life cycle. Once the development of the oral opening is complete the scyphopolyp will begin to acquire photosynthetic algal symbionts. After acquiring the needed amount of Symbiodinium and when temperatures exceed 20◦C, these scyphistomae will begin to strobilate through a process called monodisc strobilation. Through this process the calyx, the spicules containing a portion of the upper tentacular part of the polyp, will constrict and eventually separate. Over the course of the following week this will transform into an ephyra, an immature medusa stage of the life cycle. The polyp will regenerate its lost tentacular portion and the ephyra will continue to grow and mature to adulthood as a sexually reproducing medusa. (Berryman, 2005; Hofmann, et al., 1996; Kitt and Costley, 1998)


Males release gametes into the water and females take them in for fertilization. (Berryman, 2005)

The life cycle of Cassiopea xamachana is similar to other scyphozoans, with alternation of generations between a sessile polyp stage (scyphistomae) and dominant mobile medusa stage. The scyphistomae reproduce asexually by budding when resources are plentiful. Each newly produced bud will settle and lead to the production of another sedentary polyp. Eventually, the scyphistomae will begin to produce the adult medusa stage through the monadisc strobilation process discussed above. This strobilation process only takes place during the winter and fall seasons despite the medusa being found year round. Typically, scyphozoans will only strobilate during the winter months. Eventually this will lead to the development of an immature ephyra which will continue to grow into a fully mature, sexually reproducing adult medusa. The medusae are gonochoristic and the females eggs will be fertilized by the sperm released from a nearby male. The female will then internally brood her young until the eggs hatch and become free swimming planula. These small, mobile larvae will preferentially settle on a specific substrate and grow into the asexually reproducing polyp to complete the life cycle. (Berryman, 2005; Kitt and Costley, 1998)

The only form of parental care in Cassiopea xamachana is the temporary brooding of developing planula larvae discussed above. This minimal amount of parental investment in brooding will only last until the cilliated planula larvae hatch from the egg envelope. This form of parental care is fundamental as cnidarians often do not invest a great deal of resources in developing offspring. (Hofmann, et al., 1996)

  • Parental Investment
  • no parental involvement
  • female parental care
  • pre-hatching/birth
    • provisioning
      • female


The time of the entire life cycle of this jellyfish is unknown.


The symbiotic relationship with Symbiodinium microadriaticum possessed by Cassiopea xamachana defines much of its behavior and habitat choice. These zooxanthellae reside in the underside of the adult medusa’s bell and require sunlight in order to photosynthesize nutrients for the organism. For these dinoflagellates to receive an adequate amount of sun, the jellyfish must establish itself upside-down in shallow waters. This symbiotic relationship allows the upside-down jellyfish to easily access organic nutrients that account for a large portion of its diet. The rest of its diet will come through predation upon plankton and zooplankton using stinging cells or nematocysts. (Berryman, 2005; Niggl and Wild, 2009)

Communication and Perception

Cassiopea xamachana uses nematocysts or stinging cells to stun or paralyze prey. The triggering mechanism for these cells is independent of the organism's nervous system. Two stimuli trigger the discharge. One is mechanical or tactile, triggering a modified cillium on the cell. The other receptor detects chemicals, more specifically amino acids. (Berryman, 2005)

Food Habits

The up-side down jellyfish has a symbiotic relationship with zooxanthellae, located in their mesoglea. The zooxanthellae helps the jellyfish obtain most of its carbon, however, it does not meet the daily metabolic needs of the jellyfish so the jellyfish must supplement their diet. They filter feed, absorbing dissolved nutrients in the water, and/or capturing prey with their tentacles.

Nematocysts or stinging cells located in the tentacles allows the jellyfish to stun or paralyze their prey. Water pressure inside a stinging cell is controlled by osmosis. The inside of the cell is hypertonic compared to the surrounding marine environment, so water would flow in if it could. Under normal conditions, this flow is prevented. However, when both stimuli are detected the membrane will change to allow water to enter into the cell. This increased pressure will evert the barbed thread that rests inside. These specialized stinging cells can only fire once, after discharge the cell will die. Therefore, these very specific trigger mechanisms are required to ensure that nematocysts are not wasted on something that is not prey or a predator.

After the prey has been captured the jellyfish begins digestion on the oral surface and moves the partly digested prey where it can be ingested by a secondary mouth. The upside-down jellyfish has mutated from other jellies as its central mouth has become occluded and various secondary mouths have been created at the ends of the manubrial branches. Most other jellies have one mouth at the center of the oral surface. (Berryman, 2005)

  • Primary Diet
  • carnivore
    • eats other marine invertebrates


Leatherback, green, and loggerhead sea turtles, feed on upside-down jellyfish. (Witham and Futch, 1977)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

The symbiotic relationship between the upside-down jellyfish and photosynthetic zooxanthellae is ecologically valuable as it provides a pathway for converting energy into usable forms for the marine ecosystem. The symbiotic relationship between the two is similar to that of the zooxanthellae and coral. Medusae always contains zooxanthellae. Newly produced scyphistomae must acquire their symbionts from feeding or absorption from the surrounding water.

Water crabs regularly use the upside down jellyfish as a form of protection. When the crabs reach the surface or the edge of the waterbed they carry the upside down jellyfish on their backs, using the tentacles as a shield. (Berryman, 2005; Kitt and Costley, 1998; Laman, 2012; Pattern Media, 2010)

Mutualist Species
  • Symbiodinium

Economic Importance for Humans: Positive

At the current date there appears to be no commercial importance for Cassiopea xamachana.

Cassiopea xamachana can be used as a bioindicator species, to integrate relevant information about phosphate availability in low nutrient environments. This may be beneficial to humans in their attempts to restore the health of the Florida Keys reef system. (Berryman, 2005; Todd, et al., 2006)

Economic Importance for Humans: Negative

The upside-down jellyfish have recently come into the spotlight as significant bioinvaders. They are being transported on live rock to the U.S. from the Indo-Pacific. Live rock is primarily collected from the edges of reefs in the Indo-Pacific. Its exportation is an important source of revenue for many small communities. The trade in live rock is not subject to quarantine restrictions in its principal markets, and therefore poses a serious threat of bioinvasion. The potential is for inadvertent or deliberate release of organisms that reside on its surfaces. Invasive species are a principal threat to biodiversity and are responsible for enormous economic losses globally. Once established in a new environment, invasive species are often difficult to control, and eradication efforts are usually ineffectual. Scyphozoans have gained infamy as an invasive species. They are capable of extraordinary population blooms that can inflict major economic losses and ecological damage. In some areas of the world, they have caused painful or life-threatening stings thus restricting access of swimmers and tourists to aquatic recreational areas, and imposing financial posses on the tourism industry. The unregulated trade in live rock presents a serious bioinvasion risk that warrants the urgent attention of regulatory bodies. (Bolton and Graham, 2005)

  • Negative Impacts
  • injures humans
    • bites or stings

Conservation Status

Cassiopea xamachana does not receive specific legal consideration; however, in Bermuda the species lives in areas that are protected by legislation that make mooring, anchoring and fishing illegal. (Berryman, 2005)


Michael Post (author), Rutgers University, Patrizia Sacca (author), Rutgers University, David V. Howe (editor), Rutgers University, Renee Mulcrone (editor), Special Projects.


Atlantic Ocean

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

World Map

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.


reproduction that is not sexual; that is, reproduction that does not include recombining the genotypes of two parents


Referring to an animal that lives on or near the bottom of a body of water. Also an aquatic biome consisting of the ocean bottom below the pelagic and coastal zones. Bottom habitats in the very deepest oceans (below 9000 m) are sometimes referred to as the abyssal zone. see also oceanic vent.


an animal that mainly eats meat


uses smells or other chemicals to communicate


having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.


animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

female parental care

parental care is carried out by females


union of egg and spermatozoan


a method of feeding where small food particles are filtered from the surrounding water by various mechanisms. Used mainly by aquatic invertebrates, especially plankton, but also by baleen whales.


having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

internal fertilization

fertilization takes place within the female's body


referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.


A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

native range

the area in which the animal is naturally found, the region in which it is endemic.


photosynthetic or plant constituent of plankton; mainly unicellular algae. (Compare to zooplankton.)


the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.


"many forms." A species is polymorphic if its individuals can be divided into two or more easily recognized groups, based on structure, color, or other similar characteristics. The term only applies when the distinct groups can be found in the same area; graded or clinal variation throughout the range of a species (e.g. a north-to-south decrease in size) is not polymorphism. Polymorphic characteristics may be inherited because the differences have a genetic basis, or they may be the result of environmental influences. We do not consider sexual differences (i.e. sexual dimorphism), seasonal changes (e.g. change in fur color), or age-related changes to be polymorphic. Polymorphism in a local population can be an adaptation to prevent density-dependent predation, where predators preferentially prey on the most common morph.

radial symmetry

a form of body symmetry in which the parts of an animal are arranged concentrically around a central oral/aboral axis and more than one imaginary plane through this axis results in halves that are mirror-images of each other. Examples are cnidarians (Phylum Cnidaria, jellyfish, anemones, and corals).


structure produced by the calcium carbonate skeletons of coral polyps (Class Anthozoa). Coral reefs are found in warm, shallow oceans with low nutrient availability. They form the basis for rich communities of other invertebrates, plants, fish, and protists. The polyps live only on the reef surface. Because they depend on symbiotic photosynthetic algae, zooxanthellae, they cannot live where light does not penetrate.

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

seasonal breeding

breeding is confined to a particular season


remains in the same area


reproduction that includes combining the genetic contribution of two individuals, a male and a female


uses touch to communicate


the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.


animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)


Berryman, M. 2005. "Upside-down jellyfish: Cassiopea xamachana" (On-line). Accessed March 03, 2012 at

Bolton, T., W. Graham. 2005. Jellyfish on the rocks: Bioinvasion threat of the international trade in aquarium live rock. Biological Invasions, 8/4: 651-653. Accessed March 04, 2012 at

Hofmann, D., W. Fitt, J. Fleck. 1996. Check points in the life-cycle of Cassiopea spp: conrol of metagenesis and metamorphosis in a tropical jellyfish. Internation Journal of Developmental Biology, 40: 331-338.

Kitt, W., K. Costley. 1998. The role of temperature in survival of the polyp stage of the tropical rhizostome jellyfish Cassiopea xamachana. Journal of Experimental Marine Biology and Ecology, 222: 79-91.

Laman, T. 2012. "The Ocean, Photo Gallery: Jellyfish" (On-line). National Geographic Society. Accessed April 25, 2012 at

Niggl, W., C. Wild. 2009. Spatial distribution of the upside-down jellyfish Cassiopea sp. within fringing coral reef environments of the Northern Red Sea: Implications for lifecycle. Helgoland Marine Research, 1: 1-7. Accessed March 03, 2012 at

Pattern Media, 2010. "Upside Down Jellyfish" (On-line). Accessed March 03, 2012 at

Todd, B., D. Thornhill, W. Fitt. 2006. Patterns of inorganic phosphate uptake in Cassiopea xamachana: A bioindicator species. Marine Pollution Bulletin, 52/5: 515-521.

Witham, R., C. Futch. 1977. Early growth and ocean survival of pen-reared sea turtles. Herpetologists' League, 33/4: 404-409. Accessed March 03, 2012 at