Résumé
Ascidians are chordates closely related to vertebrates, including humans, and are widely used as model organisms in developmental biology to study embryonic formation and development. Ascidian development is highly stereotyped at the cellular level. Here, we present a systematic quantitative analysis of nuclear position dynamics relative to the cell apical surface during ascidian gastrulation using 3D+t fluorescence microscopy. We identify a previously undescribed stereotyped behavior in which nuclei transiently migrate toward the apical surface during interphase and retract before division, with dynamics that are reproducible within tissues. These results provide new insights into the regulation of nuclear positioning during gastrulation and motivate future experimental studies on the functional role of nuclear migration in ascidian embryogenesis.