Laboratory observation and a new discovery report on the asexual reproduction of Aurelia coerulea polyp

The moon jellyfish (Aurelia spp.) is a cosmopolitan species and often blooms to cause detrimental effects on human enterprises in many coastal waters. A population explosion of the sibling species Aurelia coerulea often occurred in the Yellow Sea and Bohai Sea in recent years. In addition, the moon jellyfish is one of the most common ornamental jellyfish in aquariums and holds great economic importance. Asexual reproduction is an important way for increasing the polyp population and expanding habitat. It is beneficial to understand the life history of the jellyfish deeply so as to grasp the asexual reproduction types and ways correctly. In this paper, we described the characteristics of asexual reproduction including stolon, budding, podocysts, longitudinal fission, and propagules reproduction by observation on more than 1000 A. coerulea polyps with a microscope. It was found that propagule bud can float under the surface of water and develop to the young polyp without sinking and adhering. A new form of rupture reproduction has been discovered, which only occurs in good condition with ample food supply. The comparison of the behavioral processes and function characteristics of six modes of asexual reproduction showed that stolon reproduction and rupture reproduction were beneficial to the rapid increase of the number of individuals in the polyp population; budding reproduction and longitudinal fission reproduction were conducive to the growth of offspring, podocysts reproduction helped the population to resist adverse environmental conditions. Propagules reproduction facilitated the migration of populations over long distances with water currents to expand or transfer habitats. Various asexual reproductions are the adaptive strategies of polyp population in response to different environmental conditions. The results are helpful to improve the breeding techniques and provide basic data for the further study of the population dynamics of Chinese coastal sea jellyfish and the exploration of the causes of large jellyfish outbreaks.