Who wouldn't sometimes like to be able to split up and be in several places at the same time? Jellyfish can do this: reproduce, for example, by simply cutting off parts from which a new individual then emerges. Biology student Anneke Heins got to the bottom of the strategies of one particular species of jellyfish.
"Cassiopea andromeda" - the name of the "upside-down" jellyfish at the centre of Anneke Heins' bachelor's thesis is almost poetic. Together with her supervisors Dr Thomas Glatzel from the University of Oldenburg and Dr Sabine Holst from the German Centre for Marine Biodiversity Research (Hamburg), she recently published the results of her live observations in the laboratory of the Biodiversity and Evolution of Animals working group at the Institute of Biology and Environmental Sciences (IBU) in the international journal "Zoomorphology".
Cnidarians - which include jellyfish - occur in different stages, including as polyps, whose characteristics include a foot disc for anchoring and a cylindrical body with tentacles. Heins focussed on the polyp generation of "Cassiopea andromeda" and describes in her work details of asexual reproduction, which produces new polyps or tiny jellyfish called ephyra. This occurs either when parts of the original polyp bud off and grow into new polyps, or by strobilation, in which the young ephyra are cut off from the top of the polyp. This type of reproduction is likely to play a decisive role in mass occurrences of jellyfish, the so-called jellyfish blooms.
The student also investigated the poisonous weapons of these animals, the cnidarian capsules (cnidae), which are used to catch prey or for defence and give the group of cnidarians their scientific name Cnidaria. Each cnid is formed by a single cell and is shed and replaced after use. When Anneke Heins scrutinised the cnidarian filaments of discharged capsules, she found a higher diversity of capsule types than expected. Differences in the number and size of capsule types in five developmental stages of "Cassiopea andromeda" could mean that the jellyfish adapts its "weapons" to changing prey preferences.
