Developmental patterning genes are redeployed during later life history stages of the upside down jellyfish, Cassiopea

Some aspects of the life cycle of the scyphozoan jellyfish Cassiopea have been described in detail. Investigations of Cassiopea have largely focused on strobilation and the unusual pattern of asexual budding at the polyp stage, in which the body wall of the polyp forms a swimming asexual bud that shows morphological and behavioral similarities to the planula. Here, we fill gaps in our understanding of Cassiopea life history by characterizing embryonic development and the process of planula metamorphosis to the polyp. We compare these processes in Cassiopea to Aurelia , the other well-characterized scyphozoan, and find notable differences. Our results indicate the Cassiopea planula shows true endoderm and ectoderm which give rise to the polyp gastrodermis and epidermis, which previous research has shown may not be the case in Aurelia . We also show that homeobox genes expressed during planula development are redeployed in a similar pattern in the asexual bud. In the newly-settled polyp, one of these genes is expressed in a pattern that breaks radial symmetry, extremely unusual in a scyphozoan. Our results suggest the potential for greater divergence among scyphozoans at planula and polyp stages and set the stage for more detailed molecular dissections of morphogenesis in organisms with metagenic life cycles.