Live imaging of the vasculature of Botryllus colonies labeled with BSA-Alexa 594 (A13101; Thermo Fisher Scientific, Waltham, MA) was carried out using a motorized fluorescence stereomicroscope MZ16FA (Leica, Germany) as previously described (Braden et al., 2014 (link)). Fixed tissue for in situ hybridization was imaged on an Olympus FluoView 1000 Spectral Confocal (Tokyo, Japan). Lipophilic staining of the vasculature labeled with CellMask Green (A37608; Thermo Fisher Scientific). Time-lapse movies (n = 5) taken as z-stacks were acquired with a Zeiss LSM 880 with Airyscan capabilities.