Cassiopea xamachana

Super Group: 
Bigelow, 1892
Cassiopea vanderhorsti Stiasny, 1922


Original description : usually 150 mm wide, flat and with rounded edges, well marked central concavity ; five lappers in each octant, short and blunt ; mouth arms, traingular in cross section, aboral surface broad and flat, with 10-15 alternate primary branches, with numerous large, rivvon shaped filaments.

The most commonly seen stage in the life cycle, the medusa, is the adult phase of the life cycle. They have 4 pairs of elaborately branched but unfused oral arms. Embedded in the mesoglea of the arms and rest of the body are thousands of zooxanthellae, giving Cassiopea xamachana its greenish color. Exact coloration within the species is variable, the most common is greenish gray-blue. The umbrella, or bell, is flat, saucer shaped and has a well-defined central depression on the exumbrella. This acts as a sucker, helping to keep the jellyfish on the bottom as it gently pulsates. As for the more conspicuous stage, the polyps are of slender design. 

Life cycle

In Cassiopea xamachana the medusae are dioecious. It is assumed that the eggs in the female are fertilized by sperm released from nearby males. The fertilized eggs are moved to knob-shaped tentacles near the center of the female where they develop into larvae. Once able to undergo metamorphosis, the larvae hatch as planulae which permanently attach to surrounding substrate with a microbial film and metamorphose into a polyp with tentacles (scyphistoma). These scyphistomae can undergo asexual reproduction via budding when food is plentiful. Each new bud will settle and form a new scyphistoma. Once the scyphistomae acquire a certain species of Symbiodinium and when temperatures reach or exceed 20ºC they will begin to strobilate. C. xamachana undergo monodisc type strobilation. Although medusae are always found containing zooxanthellae, they do not pass this onto their larvae. Each scyphistoma must acquire its own zooxanthellae from the surrounding seawater through absorption or in conjunction with feeding, to complete its life cycle. 
As noted above, C. xamachana undergo strobilation during the summer and early fall, and that their medusae are seen all year round. This is a unique trait for this species as other temperate-zone species of scyphozoans undergo strobilation during the winter and their medusae disappear during this time. It appears that the tropical C. xamachana has “cold-sensitive scyphistomae and more temperature-tolerant medusae”. 
It has also been observed that the plaulae of C. xamachana are rather selective about where they settle. If present, the planulae will settle on submerged, degrading leaves of the Red Mangrove Rhizophora mangle. This is often the case when the C. xamachanaare living in ponds surrounded by mangroves or mangrove swamps. They are even as selective as to prefer the shady side of the leaves. But most interesting is perhaps the natural, chemical cues received by the  larvae to both settle and metamorphose on the leaves . 

Original description

Order Rhizostomeae

Cambridge U Order Rhizostomeae. Marine Biological Association of the United Kingdom, Cambridge University Press (CUP),

Observation site(s)


Displaying 1 - 10 of 10
Association with... Region origin Name of site In reference...
Symbiodinium sp. Quintana Roo
Symbiodinium sp. Quintana Roo
Symbiodinium sp.
Symbiodinium sp. Hawaiian Islands
Symbiodinium sp.
Stat M, CARTER D, HOEGHGULDBERG O (2006) The evolutionary history of Symbiodinium and scleractinian hosts—Symbiosis, diversity, and the effect of climate change. Perspectives in Plant Ecology, Evolution and Systematics 8:23 - 43. doi: 10.1016/j.ppees.2006.04.001
Symbiodinium sp. Virgin Island St Croix
Symbiodinium microadriaticum Quintana Roo
Symbiodinium microadriaticum
Symbiodinium microadriaticum Florida
Symbiodinium pulchrorum