Cardiopharyngeal mesoderm development. a Schematic diagram of the cell divisions of the B7.5 lineage in Ciona robusta, up to the specification and migration of the trunk ventral cells (TVCs). ATMs, anterior tail muscles. Vegetal views in all panels except the last panel, which shows a lateral view (left side only). b Diagram indicating the divisions of the TVCs and specification of heart and atrial siphon muscle precursors. STVCs, secondary TVCs; FHPs, first heart precursors; SHPs, second heart precursors; ASMFs, atrial siphon muscle founder cells; ASMPs, atrial siphon muscle progenitors; LoMPs, longitudinal muscle progenitors. Colored arrows indicate cell migration events (TVCs, ASMPs). c Gene expression patterns in the B7.5 lineage. 1st panel: in situ hybridization for mCherry mRNA (red) expressed in the B7.5 blastomeres by a Mesp > mCherry reporter plasmid. Nuclei stained by DAPI (blue). All other panels show mRNA in situ hybridization for endogenous gene expression in embryos electroporated with Mesp > LacZ reporter plasmid. Immunostaining for beta-galactosidase, the product of the LacZ gene, reveals the descendants of the B7.5 lineage throughout development (red nuclei). Dotted lines indicate ventral midline of the embryo. See text for details. a Adapted from Stolfi et al. . b and c Adapted from Kaplan et al.