Fig. 4: Schematic illustration showing differences between spiny- and soft-ray development in Melanotaenia praecox.

In spiny-ray development, mesenchymal cells (green) condense at the tips of spiny-ray bones, and the layer of extracellular matrix (ECM) (yellow) surrounds mesenchymal cells. In soft-ray development, the actinotrichia (magenta) are distributed at the tips of soft-ray bones and serve as scaffolds for mesenchymal cells (green). Micro-CT scan images were used to schematically illustrate the fin bones.