Developmental Stereotypy Assessment in Ascidian Embryos

Embryogenesis, a central focus of developmental biology, is the de-velopment of a fertilized egg into tissues and organs. Comparing the development of individual embryos helps identify similarities and variations, providing a starting point to identify constraints acting during embryogenesis. Recent live microscopy techniques allow to acquire temporal series of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$3\mathrm{D}$</tex> images, giving an unprecedented means to study developing embryos. This study focuses on ascid-ian embryos as the cellular stereotypy of their development enables investigations at the cellular level. More precisely, we propose a methodology to assess the extent of variation in the orientation of cell divisions. From a population of imaged embryos, we demon-strate that the cell division orientation of some cells unexpectedly exhibits a bimodal distribution.