Fig. 3

Larval epithelial cells transform into archeocytes during early metamorphosis. Nuclei are stained with DAPI (blue), and subsets of cells are labeled with CM-DiI (red) or phallacidin (green). a A confocal section of a competent larva labeled with CM-DiI. CM-DiI-labeled cells are present only in the epithelial layer of the larva. The dotted line indicates a boundary between the epithelial layer and subepithelial layer with the inner cell mass. b Confocal section of the larval epithelial layer showing ciliated columnar epithelial cells labeled with CM-DiI (arrowhead, circled by dotted line). Globular (spherulous) cells are non-specifically labeled by phallacidin (arrow, circled by dotted line). c Confocal section of archeocytes found during early metamorphosis in 24 hpr postlarvae. d A high-magnification image of an archeocyte. Small DAPI signals (arrows) are putative nuclear fragments obtained via phagocytosis of larval cells that underwent apoptosis at metamorphosis [28, 42]. The arrowhead shows the much larger and less heavily stained nucleus (with a nucleolus) of this archeocyte. Scale bars a 40 μm; b–d 15 μm