Embryonic development of the moon jellyfish (Cnidaria, Scyphozoa): another variant on the theme of invagination.

Background: (Scyphozoa, Cnidaria) is an emblematic species of the jellyfish. Currently, it is an emerging model of Evo-Devo for studying evolution and molecular regulation of metazoans' complex life cycle, early development, and cell differentiation. For , the genome was sequenced, the molecular cascades involved in the life cycle transitions were characterized, and embryogenesis was studied on the level of gross morphology.

Embryonic development of thecate hydrozoan Gonothyraea loveni (Allman, 1859).

Progress of Evo-Devo requires broad phylogenetic sampling providing the data for comparative analysis as well as new objects suitable for experimental investigation. Representatives of the early-branching animal phylum Cnidaria and particularly hydrozoans draw great attention due to the high diversity of embryonic and post-embryonic development and life-cycles in general. Most detailed studies on embryonic development in hydrozoans were performed on the species shedding their gametes with subsequent embryo development in the water column.