Potential for artificial symbiosis between marine microalgae and invertebrates: I. survival of marine microalgae injected into the medusa of the moon jellyfish Aurelia aurita

Some marine microalgae and cyanobacteria form mutualistic symbioses with diverse invertebrates, particularly cnidarians. Among microalgae, dinoflagellates in the family Symbiodiniaceae are the most well-known symbiotic partners of jellyfish and corals. However, the symbioses involving other dinoflagellate families, nano- and micro-flagellates, diatoms, and cyanobacteria with cnidarians are not well understood. As an initial step, it is essential to explore the survival of these microorganisms inside cnidarians. We monitored the survival of eight microalgal species (nine strains) and one cyanobacterium species every day for seven days after injecting each into the medusa of the moon jellyfish <i>Aurelia aurita</i>. The dinoflagellates <i>Effrenium voratum</i> (free-living [FL] and living-in-coral strains), <i>Cladocopium infistulum</i>, <i>Prorocentrum cordatum</i>, <i>Prorocentrum koreanum</i>, <i>Symbiodinium microadriaticum</i>, the prasinophyte <i>Tetraselmis suecica</i>, the chlorophyte <i>Dunaliella salina</i>, and the raphidophyte <i>Heterosigma akashiwo</i> survived inside the medusa, while the cyanobacterium <i>Synechococcus</i> sp. was not detected. Additionally, <i>E. voratum</i> (FL) survived within the medusa for 60 days and gradually spread to adjacent areas, indicating potential for artificially established symbiosis. The results of this study provide a basis for artificial symbiosis between microalgae and invertebrates.