Figure 3.

Animals that can produce monozygotic (MZ) twins or quadruplets. (A) The zebrafish janus mutant exhibits the separation of two groups of blastomeres prior to the eight-cell stage, resulting in the development of two distinct spheres (yellow) that ultimately lead to the formation of conjoined fish. If there is limited space between the two groups of cells, the blastomeres and marginal zones (dark blue) will merge during development. (B) To generate MZ quadruplets, zygotic splitting of nine-banded armadillo embryos happens after implantation. The substantial enlargement of the exocelom cavity (blue) functions as a physical force, causing the division of the embryonic shields that develop from the epiblastic plate (yellow), and effectively separating them into distinct spaces that remain unconnected.