The upside-down jellyfish Cassiopea increasingly occurs in many (sub-) tropical coastal habitats such as mangrove forests, seagrass meadows, and coral reefs. Its mixotrophic lifestyle and ecophysiological plasticity as well as a high regenerative capacity may be reasons for its success. While the regeneration of umbrella tissue and body structures (i.e. rhopalia and oral arms) was already demonstrated, it remains unclear whether a fully functioning medusa can regenerate from only umbrella tissue. In this study, we thus investigated the regeneration of umbrella fragments over time. We conducted a laboratory experiment for which we used 18 Cassiopea medusae of three different size classes that were cut into two pieces each, one fragment with oral arms and one without. Over a total observation period of 5 weeks, we regularly monitored survival, pulsation behavior, growth and the regeneration pattern of fragments. Findings revealed that 100% of the fragments with oral arms and 88% of the fragments without oral arms survived. Pulsation behavior occurred in all fragments and lasted until the end of the experiment in 94% of all fragments. The umbrella area of fragments without oral arms showed a significantly higher decrease in the first two weeks compared to fragments with oral arms. A complete regeneration of umbrella tissue was observed in all fragments, with and without oral arms alike, and 50% of all fragments even regenerated rhopalia or oral arms as body structures after 33 days. These results suggest an outstanding regenerative capacity of Cassiopea jellyfish after fragmentation. This may contribute to (i) explain the currently observed success of upside-down jellyfish and (ii) extend our knowledge about its regeneration process, which might even act as an asexual reproduction mode in Cassiopea.

颠倒的水母仙后属越来越多地发生在许多（亚）热带沿海栖息地，如红树林、海草草地和珊瑚礁。它的混合营养生活方式和生态生理可塑性以及高再生能力可能是其成功的原因。虽然伞状组织和身体结构（即rhopalia和口腔臂）的再生已经得到证实，但功能齐全的美杜莎是否可以仅从伞状组织再生仍不清楚。因此，在这项研究中，我们研究了伞碎片随时间的再生。我们进行了一项实验室实验，我们使用了 18仙后属三种不同大小的美杜莎，每个被切成两块，一块带有口臂，另一块没有。在 5 周的总观察期内，我们定期监测碎片的存活、脉动行为、生长和再生模式。结果显示，100% 的带有口臂的碎片和 88% 的没有口臂的碎片幸存下来。脉动行为发生在所有片段中，并且在所有片段中的 94% 中一直持续到实验结束。与有口腔臂的片段相比，没有口腔臂的片段的伞形区域在前两周显示出显着更高的减少。在所有碎片中都观察到伞状组织的完全再生，无论有无口臂，33 天后，所有碎片中的 50% 甚至再生 rhopalia 或口臂作为身体结构。仙后属破碎后的水母。这可能有助于 (i) 解释目前观察到的倒置水母的成功，以及 (ii) 扩展我们对其再生过程的了解，这甚至可能充当无性繁殖模式仙后属.