ИСТИНА

Current knowledge on body axis formation in Cnidaria is restricted to a handful of species, limiting our perspective about the evolution of developmental mechanisms, both within the group, and in comparison to bilaterians. Notably, the molecular regulation of embryonic axis development in Scyphozoa, a major medusozoan clade, remains largely unexplored. In this context, we have started developing the Mediterranean scyphomedusa Pelagia noctiluca as an experimental model. Pelagia life cycle is simplified, and does not exhibit a polyp stage: four days after fertilization, the planula larva transforms directly into the juvenile ephrya, which already possesses the adult radial body plan. The absence of a polyp phase opens the possibility of addressing the specification of medusa body plan with functional tools, which we are currently developing. Moreover, fundamental for developmental studies, a large number of eggs and synchronized embryonic stages can be obtained daily in our laboratory, where the entire life cycle is now controlled. Our preliminary work has shown the potential of this species for developmental studies, and we present a detailed morphological description of early development, together with the first expression patterns of several candidate oral-aboral axis regulators. In addition, grafting and bisection experiments have started to provide information about the regulation of body axes formation. These data allow for a better understanding of axis specification from egg to ephyra in a scyphozoan. This project is funded by RFBR 15-04-08214-а, ANR MEDUSEVO–ANR-13-PDOC-0016 and EMBRC-Fr OOV-2016-658, AAP2017–952.