Fig. 3: The cell and extracellular matrix (ECM) conditions at the tips of spiny rays in Melanotaenia praecox.

a Cell, collagen, and bone conditions of the dorsal fin in a larva at DFst-4 (n = 3). The upper left panels are 3D light-sheet images of the dorsal fins, and the other panels are virtual sections of the 3D images. The tips of spiny rays and soft rays are indicated by yellow arrowheads. The location of the virtual sagittal section of the spiny and soft rays shown in the lower left panels is indicated by the yellow dashed box in the upper left panels. The location of the virtual transverse section of the spiny and soft rays shown in the right panels of each fin is indicated by the dashed line in the lower left panels. The lower right panels of each fin are magnified images of the yellow dashed box in the upper right panels. b Ultrastructural analysis of the spiny rays in DF-st4 larvae by TEM (n = 3). First-dorsal-fin sections showing the structural organization of the spiny-ray tip. The lower panels show the TEM images labeled for mesenchymal cells (green), a spiny ray (orange), basement membrane (yellow) and basal lamella (hot pink). The numbers of each panel (#1, #2) correspond to the numbers in magenta dashed boxes. c Distribution of laminin (green) and TP63-positive cells (magenta) in the spiny rays of a DF-st4 larva, counter-stained with DAPI (white) (n = 9). Images in panel c are virtual sections of the same sample by confocal microscopy. The locations of the virtual transverse section shown in the lower panels are indicated by the dashed line in the upper panel.