Fig. 1. Zebrafish valves form through invagination. Larvae were stained with rhodamine-phalloidin and imaged using confocal microscopy at 76 (A) or 62 (E) hpf, or imaged using SPIM at 76 (B), 85 (C,D) or 63 (F) hpf. Although by confocal microscopy a superior endocardial cushion appears to be present (panel A), SPIM imaging shows that this structure is actually a valve leaflet (B-D). Arrow in panel A points to the presumed endocardial cushion and that in D to the valve leaflet. No intermediate stage of mesenchymal cells was observed by either confocal (E) or SPIM imaging (F). A, atrium; V, ventricle.