Whole-Embryo 3D Quantification Reveals Conserved Topological Design and Scaling of Germ Layers in Xenopus

How embryos of different sizes generate reproducible body plans remains a central question in developmental biology. Do larger embryos contain more cells, or preserve conserved organizational principles that ensure robust tissue patterning independent of scale? Here, we address this question through whole-embryo quantitative mapping of cell number, tissue allocation, and spatial organization during early development in Xenopus. Using optimized in-toto 3D imaging, tissue clearing, and deep-learning for nuclei segmentation, we quantified cell numbers and reconstructed the spatial distribution of cells in early embryonic stages. Although X. laevis embryos exhibited substantially larger embryo volumes and higher total cell numbers than X. tropicalis, the proportional allocation of cells among ectoderm, mesoderm, and endoderm remained highly conserved between species. In addition, quantitative analysis of local cellular neighborhoods revealed striking conservation of spatial order, packing geometry, and large-scale tissue architecture despite major differences in embryo size and cellular density. Together, these findings demonstrate that early vertebrate embryos follow shared quantitative design principles in which embryonic scaling occurs without disruption of the underlying cellular blueprint of the body plan. Our study establishes a quantitative framework for comparing embryonic architecture across species and provides evidence that developmental organization is governed by conserved scale-invariant topological principles.