Fig. 6

Development of the vascular segments in the turtle Pelodiscus. OFT cushions (from proximal to distal) and NCC contribution, movat and TFAP2α staining. a In the proximal OFT only the septal cushion is prominent between the cellularized cardiac jelly. b The septal cushion containing condensed mesenchyme becomes flanked by the other cushions. Here, a cell-rich whorl is present, pointed to the parietal cushion. c Magnification of an adjacent section, negatively stained for TFAP2α. d Another condensation (rich in SHF, #) separates both aortae. The myocardial wall on the dorsal side is retreating. e The three arterial trunks are separated. Note that a spur of myocardium (arrow) protrudes into the NCC area (*). f The carotid trunk (3 + 3) branches off the systemic aorta. The myocardial sleeve is not longer present. g Positive TFAP2α in the inner wall of the carotid trunk (3 + 3). h The inner media of the carotid trunk is rich in glycosaminoglycans compared to the adjacent arteries, giving it a spongy appearance. Abbreviations as in Fig. 3. i Cross section of the neck region of an embryo of Emys orbicularis showing the carotid trunk (3 + 3). The arterial wall is not spongy as in Pelodiscus (compare h). The Emys embryo belongs to material described earlier by our group [50]