Progressive Cellularization of Blastoderm and Extraembryonic Tissue Formation in the Ant Camponotus floridanus.

Blastoderm formation represents a key transition from a syncytial to a cellular embryo and provides the basis for subsequent embryonic patterning in insects. In most insect models, this transition occurs through synchronous cellularization, producing a uniform blastoderm that is patterned only afterward. Whether this sequence represents a common developmental principle across insects remains unclear. Here, we show that in the carpenter ant Camponotus floridanus, cellularization proceeds progressively rather than synchronously and establishes spatially differentiated blastoderm domains. Cellularization initiates at the anterior and progresses posteriorly, while a second front from the posterior advances in the opposite direction. These opposing fronts converge at the site where the germline capsule subsequently forms. At the same time, a regionalized blastoderm rather than a uniform blastoderm is established. The extraembryonic tissues amnion, serosa, and trophocytes emerge along progressive cellularization through coordinated morphogenetic dynamics and exhibit a distinct mode of organization. Our data present a revised understanding of cellularization of blastoderm in insects and broaden the comparative framework of embryogenesis described in model organisms.