Mangrove Jellyfish

Cassiopea xamachana



Kingdom Animalia

Phylum Cnidaria

Class Scyphozoa

Order Rhizostomeae

Family Rhizostomatidae

Other Names:

Mangrove jellyfish
Upside-down jellyfish
Cabbage-head jellyfish (name also given to Stomolophus meleagris, a close relative)
Many-mouthed jellyfish (name also shared with other jellyfishes in the same order, Rhizostomeae)


Cassiopea xamachana has a bell, which can be gray-green to brownish-yellow in color with its edges being round and rather flat. The colors are reflected from algae living within its tissues. The feeding tube is fairly stout with 8 long, green or brown, fleshy oral arms with grapelike clusters on 15 primary branches and several large, ribbon-shaped filaments suspended beneath. Its mouth is subdivided into many tiny pores on oral arms. They are generally about 2’’ (51mm) high, and 12’’ (30cm) wide (Meinkoth, 1981). C. xamachana are colonial organisms and tend to exist in large swarms (up to thousands) and can be seen lying side by side on their backs in shallow waters exposing their oral arms to the currents (Meinkoth, 1981).


The common name associated with this particular species of jellyfish (mangrove jellyfish) pretty much gives away the location of its habitat. That is, the mangrove jellyfishes live in a type of habitat called, “mangroves.” The mangroves that C. xamachana  are more commonly found in are in areas such as the Gulf of Mexico, the Caribbean, and in areas of tropical climate such as Central and South America. Specifically, it lives primarily in the warm shallow waters of mangroves (which are swamps) around the roots that are characteristic of this type of saline wetland. Mangroves distinctively have high sediment contents due to flowing waters. An adaptive feature that the vegetation forms as a response to this issue would be the formation of a type of root called, “pneumatophores” which allows them to breathe in this sandy and muddy type of environment that mangroves are known to have. This creates an environment that is suitable for the mangrove jellyfish as well as many other marine invertebrates in tropical areas because the roots aerate the water and shallow conditions provide ample amounts of sunlight for the photosynthetic algae that lives inside it (Moore and Turner, 1991).

The photosynthetic algae, zooxanthellae and C. xamachana have a symbiotic relationship with one another. The jellyfish benefits by obtaining the excess nutrients that the algae produce after photosynthesis. In return, the alga is provided with a host that lives and swims in areas where conditions are appropriate for the photosynthesis that it requires to survive (Santos, 2001).

In addition to feeding on zooxanthellae, C. xamachana also feeds on plankton that can be sucked in through their many mouths, thus they are also called, “the many-mouthed jellyfish” (N. Marshall, 1971; O. Marshall, 1971). C. xamachana has a primary mouth that functions in breaking down the food before passing it on to its secondary mouths that face upward toward the surface water (Andon& Urban, 2010). The two most common habitats of C. xamachana are mangrove swamps and sea grass beds. Unfortunately, these two areas are said to be the most threatened habitats on Earth in that humans easily come into contact with these areas and are destroying them due to coastal development (Tennessee Aquarium, n.d.).

Life Cycle & Reproduction

C. xamachana reproduce by an asexual process called, “strobilation” in which the small polyps (characteristic of most Scyphozoans) undergo a budding process when the water warms in the spring time. Small medusae then break off from the polyp and mature usually by the end of summer. At maturity, the scyphomedusae release their sex cells before dying. Fertilization occurs in a free-swimming larva that eventually attaches to the bottom or to a hard substrate and develops again into a polyp.

Defense Mechanisms

Most often people tend to mistake C. xamachana as flowers or algae in the water due to the upside down orientation in which they place themselves for almost their entire life. The coloration they have also works to their advantage by helping them resemble underwater vegetation more.

Stinging Cells    
As with most other jellyfish, C. xamachana release strings of mucous containing a special type of stinging cell when they feel threatened. These venomous stinging cells are called, “cnidocytes.” Although a single sting may not be deadly, the real danger is that once a single jellyfish is triggered, the whole swarm comes up and this is where it poses the greatest danger for any human coming into contact with this jellyfish.

Ecological Importance

There is currently no major ecological importance of C. xamachana

Summary of recent research

A recent study conducted on Cassiopea xamachana found that they are capable of accumulating trace elements above ambient seawater concentrations and that it is also possible to discriminate different geographical populations based on chemical signatures in their tissues.  Researchers concluded and suggested that while the persistence of C. xamachana in polluted systems have been documented, historically jellyfish have not been considered useful biomonitors, however, we should consider using them as a future tool in the biomonitoring toolbox as they meet all of the key criteria that an organism needs to have to be an effective biomonitor (Templeton & Kingsford, 2009).

Personal Interest

I chose to study the mangrove jellyfish because I actually don’t know very much about jellyfish at all and thought that this would be a great opportunity to learn more about them. Prior to doing the research needed for this report, I only knew that jellyfishes in general: sting, are translucent soft-bodied creatures with myths such as peeing on the site of being stung to remedy the pain and are often found in marine environments. Now, I understand much more about them and am fascinated with them, especially in their unique adaptations from their ability to gain nutrients from a symbiotic relationship with the zooxanthellae, to their mechanism of floating upside-down to maximize both theirs and the algae’s nutrient gain by capturing sunlight in the shallow waters they live in. It really amazes me how all these different adaptations work together in an organism that initially to me looks seemed more vulnerable than other animals, but ended up being truly more complex than I thought. I am now much more interested in jellyfish and am really glad I picked this animal as the subject of my report.

Literature Cited

Please note that the following references may have either been removed or relocated by the webpage owners since the time this student report was created.

Andon, A., & Urban, C. (2010). Jellyfish Art, Jelly Fish Species (part 1). Retrieved May 25, 2011, from: URL (

Marshall, N. B., & Marshall, O. (1971). Ocean Life. New York, NY: Blandford Press Ltd.

Meinkoth, N.A. (1981). National Audubon Society: Field Guide to Seashore Creatures (pp. 363-364). New York, NY: Alfred A. Knopf, Inc.

Moore, P. D., & Turner, B. D. (1991). Saline Wetlands. In
P. Moore (Eds.), Encyclopedia of Animal Ecology (pp. 88-89). Hong Kong: The Promotional Reprint Company Limited.

Santos, S.R. (2001). WGBH Educational Foundation, Clear Blue Skies Production, Inc. Coral Reef Connections. Retrieved May 25, 2011, from: URL (

Templeton, M.A., Kingsford, M.J. (2009). Trace element accumulation in Cassiopea sp. (Scyphozoa) from urban marine environments in Australia. Marine Environmental Research, Volume 69, Issue 2, pp 63-72, doi: 10.1016/j.physletb.2003.10.071

Tennessee Aquarium,(n.d.). Retrieved May 24, 2011, from: URL ( 

Wu, N. (photographer). (2005). (JEL71) upside-down jelly
(Cassiopea xamachana), Retrieved May 26, 2011, from: URL

External Links:

Please note that the following external links may have either been removed or relocated by the webpage owners since the time this student report was created.