The umbrella of this species has a diameter of about 60 centimeters, its black oral tentacles are up to 2 meters long: The giant jellyfish Rhizostoma luteum was discovered in 1827 in the western Mediterranean. It was so rare, however, that many long doubted its very existence. The matter was decided after these giant jellyfish repeatedly washed ashore on the beaches of Morocco and Spain.
The marine biologist Karen Kienberger from Jellyfish Research South Spain captured an individual for her research. When she discovered that the jellyfish was sexually mature in the laboratory, she delivered some of its planula larvae to the zoo. Very little at all was known about this species, and the captive breeding effort proved to be a real challenge. Nonetheless, the first offspring were successfully raised artificially for the first time anywhere. Since then the growth and development of this fascinating cnidarian have been investigated in great detail.
The aim is to significantly improve the currently poor data on the biology of Rhizostoma luteum. The next step will be to study the potential impacts of climate change on the reproduction of these jellyfish in the wild.
Research on jellyfish is a hot topic going far beyond the important basic research level. The specter of future mass jellyfish occurrences in warmer seas is attracting the attention of experts worldwide.
A small laboratory has been installed in the basement of the Aquarium House. This is where the influence of different temperatures and salinities is being tested on the development of the giant jellyfish. Flashlights, magnifying glasses and microscopes are being used to document the growth of the polyps, which are initially less than 1 millimeter long. The zoo was able to produce the first photographs of all of the developmental stages of the giant jellyfish. The newly gained data were sent to Karen Kienberger to advance her research.
Kienberger K, Riera-Buch M, Schönemann AM, Bartsch V, Halbauer R, et al. (2018) First description of the life cycle of the jellyfish Rhizostoma luteum (Scyphozoa: Rhizostomeae). PLOS ONE 13(8): e0202093. https://doi.org/10.1371/journal.pone.0202093