Fig. 6

a Snapshots from Supplementary Movies ¹ and ², showing WT and MZsmad4a embryo development. Upper and lower panels show developing WT and MZsmad4a mutant embryos, respectively. Embryos are shown at 0.0 (mid gastrulation), 3.0, 6.3, and 10 h after acquisition onset. Nuclei were mosaically labeled with PSmOrange. Scale bar corresponds to 150 µm. b Schematic of the OPT set up, where up to five embryos can be imaged simultaneously. A 5-channel image is generated for each embryo for subsequent quantitation. c–f Examples of processed WT and MZsmad4a embryo images. Merged nuclear marker channel together with anterior (otx2) and posterior (myod) markers and digital skeleton (c). Merged anterior (otx2) and posterior (myod) markers and skeleton (d). Skeleton channel, together with anterior/posterior landmarks (e). Green spheres along the skeleton mark A/P coordinates. Segmented embryo mask representative of the nuclear marker (f). Scale bars correspond to 260 µm. g A subset of morphological descriptors from the output array (4 out of 26). Note that all measures, beside the A/P index, refer to the segmented embryo mask. Box-and-whiskers plots show WT (n = 6) vs MZsmad4a mutants (n = 4). Box at 25–75^th percentile, whiskers at minimum and maximum values, line at median. Solidity: p = 0.009, Skeleton distance to surface (variation): p = 0.009, Tortuosity p = 0.019, Principal axis length ratio L3/L1: p = 0.009. Two sided Mann–Whitney test. *p < 0.05; **p < 0.01.