Upside-Down Jellyfish
    (Cassiopeia xamachana)

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Name: Upside-Down Jellyfish
Scientific name: Cassiopeia xamachana
Range: southern Gulf of Mexico, Caribbean, and other tropical waters
Habitat: Shallow water, often in mangrove swamps
Status: Not threatened 
Diet in the wild: Most food is produced by symbiotic algae that live in their tissues and plankton 
Diet in the zoo: Fish, marine invertebrates, zoo plankton 
Location in the zoo:  James R. Record Aquarium (not currently on exhibit)

Physical description: 

  • they reach 12-14 inches in diameter
  • they reproduce sexually in one part of their life and asexually in another part.
  • they have lacy frilly ruffles
  • they appear to glow in the dark
  • they contain symbiotic golden algae

  • General information: 

    Upside-down jellyfishes have more than 40 mini mouth openings.  They are invertebrates and their bodies are 95% water, 3% salt, and 2% protein.  It usually lies on the bottom of the water and is mistaken for the sea anemone.  They have a sting, but it isn't very poisonous or deadly.  They also don't sting very often. Symbiotic algae living in the jellyfish's body produce oxygen; this allows the jellyfish to survive in oxygen-poor water.  


    Special anatomical, physiological 
    or behavioral adaptations:

    The jellyfish starts out as free swimming organism, and as soon as it reaches 2 cm. it inverts its bell and goes to the bottom of the water where it lands upside-down. 

    Like many other jellyfish, Upside-Down Jellyfish have a life cycle in which the jellyfish stage alternates with a polyp stage.  New jellyfish are produced by budding from the polyps.  

    Several upside-down jellyfish swimming around.

    Comments about the upside-down jellyfish of the Fort Worth Zoo:

    The zoo keeper said that he was there when they had the jellyfishes, and that the upside-down jellyfish came there as an accidental transfer from the food source.  They had had them for about a year and they were doing well, breeding and everything else.  The zoo keeper said that they gave some of them away; however the population at the zoo was allowed to die out to make room for a sea horse project. 

    Personal Observations: When I went to the exhibit, I was informed that the upside-down jellyfish were no longer being shown there.  From what I've seen and heard though, the upside-down jellyfish are very beautiful.  I also understand that they feel very slippery and kind of slimy.
    Source Materials and Related Links: Note: I used two books for the web page: 

    1) "Harper and Rows Complete Field Guide to North American Wildlife, Western Edition, assembled by Jay Ellis Ransom, copyrighted in 1981 

    2) "Harper and Rows Complete Field Guide to North American Wildlife, Eastern Edition, assembled by Henry Hill Collins, Jr., copyrighted in 1959 

    Page author: {short description of image}Keundra Carraway 

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