Carbon distribution strategy of Aurelia coerulea polyps in the strobilation process in relation to temperature and food supply

Mass occurrences of moon jellyfish have been observed in coastal waters. Strobilation directly determines the initial population size of adult jellyfish, but energy distribution during the strobilation process is not well understood. In this study, strobilation was induced in polyp of Aurelia coerulea by elevating temperature. The different stages in the strobilation process, including polyp budding, strobilation and body growth, were investigated at six temperature levels (8, 10, 13, 15, 17 and 19 degrees C) and five food supply levels (0, 30, 60, 100 and 150 mu g C/L). The results showed that the duration of strobilation preparation stage (SP) remarkably decreased with increasing temperature. Food level positively affected the production of buds and ephyrae and the body growth of parent polyps. Of the six temperatures tested, 13 degrees C was optimal for strobilation. At 13 degrees C, strobilation activity was enhanced, and this treatment resulted in the greatest energy distribution, highest ephyrae production and longest duration of strobilation stage (SS). Polyps tended to allocate 6.58%-20.49% carbon to buds with sufficient food supply regardless of temperature. The body growth of parent polyps was highest at lower temperatures and higher food levels. This study is the first to provide information on carbon-based energy distribution strategy in the polyp strobilation process. We concluded that budding reproduction is a lower-risk strategy for A. coerulea polyps to increase populations. Even during strobilation season, polyps prioritize budding, but at the optimal strobilation temperature, polyps utilize a portion of the energy stored for budding to release ephyrae. The body carbon content of parent polyps may be considered as strategic energy reserves, which could help to support budding activities and strobilation during harsh conditions.