Additional file 2: Figure S2.

Apoptosis, loss of epithelial integrity and phagocytosis at early metamorphosis in A. queenslandica. A-C: Free-swimming larva. D-F: Settled postlarva, ≤7 hours post-settlement. G: Settled postlarva, ≤12 hours post-settlement. H: Mat-formation postlarval stage. DAPI is used to label DNA. In A, B, D, E and G, DNA fragmentation is detected by TUNEL assays (TUNEL). In C, F and G, specimens are labelled with an anti-Tyrosinated-Tubulin (tyrTub). A: A confocal longitudinal section through the larva; anterior is down. A boxed region in A is shown in B; note that TUNEL-positive fragmented DNA (arrowheads) localises within the most anterior domain where cuboidal cells reside. C: A confocal section through the outer layer epithelium; note that the epithelium consists of a continuous sheet of cells with apical cilia (ci) and basal, typically anucleolated, nuclei (nu). D: Confocal medial sections viewed from the top of the metamorphosing postlarva. A single section through the outer layer epithelium in the boxed region in D is shown in E. F: A confocal section showing the surface view of the distintegrating outer layer epithelium; note the breakup into smaller, tightly packed cells with anucleolated nuclei (the fragmented epithelium; fr). G: A confocal section of an outer-most region of the metamorphosing postlarva; note the lack of an epithelium, and the presence of phagocytised TUNEL-positive apoptotic bodies (arrowheads). H: A confocal section through an archeocyte in a mat-formation-stage postlarva labelled with DAPI and an anti-tyrTub, in which larval archeocytes and ciliated epidermal cells were simultaneously labelled (with EdU and CM-DiI, respectively) and followed through metamorphosis. Note intracellular CM-DiI-positive cellular fragments containing DAPI-positive nuclear materials (arrowhead), the presumptive apoptotic bodies, in an EdU-positive archeocyte of larval origin. Abbreviations: ep outer layer epithelium; icm inner cell mass. Scale bars: 100 μm (A, D, E), 10 μm (B, C, F-H).

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Nakanishi et al. BMC Biology 2014 12:26   doi:10.1186/1741-7007-12-26