Belongs to the Order Rhizostomae, Family Cepheidae. One of the most common jellyfish in the Mediterranean sea and definitely the most colorful of all. Usually they are found in great numbers in the Aegean and the Adriatic sea. The animal can grow to 35 cm in diameter (the animal shown in the following series of pictures is a fully grown adult) and in contrast to most jellyfishes has an ability to move on its own (does not necessarily follow water currents). In the sea it is a magnificent animal. It migrates vertically while various juvenile fishes are associated with it. In the photos shown, the fishes which live around and in it are juvenile Seriola dumerili.
C. tuberculata has separate sexes and the eggs are fertilized internally, the larvae kept in pockets and then are released in the open water where they developed into sessile polyps.
This species is not recommended for aquaria for two reasons: First, it feeds on microplankton and second they need an extremely wide aquarium in order to avoid hitting the aquarium glass which will damage it. Stay assured that if I could keep it, I would. The way it majestically moved in the water coupled to the colorful and unique appearance would make a nice addition to any Mediterranean tank.
Morphologically it is characterized by a flattened region along its margin and has a dome at the center of its umbrella giving it the appearance of a large fried egg when viewed of above (see photos below). There are many, variable-length tentacles attached to eight lappets. It has eight oral arms which are brittle, short and fused proximally. Numerous blue or purple tipped appendages are located between each of the oral arms. These colors are due to the presence of unicellular symbiotic algae (zooxanthelle).
It is found in aggregations in the open water of the high seas and along coastlines.
Photos taken in Aegean Sea (Saronic gulf) in September 2003.
New In March 2004, the following question was sent to MCH by James White, London, UK:
I was swimming in the Mar Menor and found myself surrounded by hundreds of what I now know to be cotylorhiza tuberculata, (thanks to your web site). I would be interested if you have any information about the seriousness of their sting.
Dr. Peter Nicolaides
Are we talking about the jelly-fish which is round, darkish-yellow-brown, fried-egg appearance on top (smooth round bump on top) with short tentacles (compact, no tentacles dangling/trailing) with a small flat whitish disc on each end, with (usually) a small school of fish darting with impunity in and out of that cluster? If it is this one, the sting is very mild in my experience and does not leave any skin lesions. However, venom strength may vary. The size of these rather impressive creatures can range from ~8-10 cm diameter to 30 or even 50 ! The best reference book available (maybe in libraries, 'cos it is quite expensive) is a two-volume monster by Halstead "Poisonous and Venomous Animals of the Sea". Last time I saw that was in the Natural History Museum in London.
If I remember well, the venom is quite complex so the only action that may relieve pain is to apply hot-water compresses (as hot as you can bear, ~45-47 C) and that should start denaturing the proteins of the venom.
Dr. Alexandros FrantzisAs far as I know Cotylorhiza tuberculata is not dangerous for human beings. I have touched or held them with naked hands many times. To give you an idea, once a colleague of mine put one of them on the top of his head as a hat(!!!) to show that it was not dangerous... Nevertheless, all jellyfish have toxins and acids that can be dangerous to a varying degree depending on where and how they can reach the human body. For example some species (like Pelagia noctiluca) are harmless if you just touch them with the "ventral" part of your fingers, but if a tentacle reaches the "dorsal" part of your hand or if just after touching it you touch your face, believe me you will have problems! Another issue is the degree of sensitivity that also varies a lot from one person to another, so I cannot completely exclude that for a very sensitive skin even Cotylorhiza could be a problem...
H. Erhardt and H. Moosleitner. In Baensch Marine Atlas, Vol. 2, Invertebrates, Mergus Verlag GmbH, Germany.
Steven Weinberg. In Decouvrir la Mediterranee, Edition Nathan, 1993.
You can see a video clip of the animal swimming in the Mediterranean.