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Fig. S1
The structural and histological organization of a caudal fin in adult zebrafish. (A-B) Live-imaging of the caudal fin. (A) The adult fin has a bi-lobed morphology, supported by an array of bones, which occasionally bifurcate. (B) Higher magnification of the framed area in (A) displays segmented bone-containing rays, called lepidotrichia, which are spanned by soft interray tissue. The schematic parallelogram depicts a transversal sectioning plane for histological analysis. (C) Transversal section of a fixed fin stained with Haematoxylin (nuclei, violet) and Eosin (cytoplasm, pink/magenta; extracellular matrix, red/orange). Rays are supported by a pair of concave bones underneath the epidermis. The interray tissue is devoid of skeletal elements and the epidermis is supported by the thickened basement membrane. The mesenchymal tissue fills the inner part of the fin, and it contains fibroblasts, extracellular matrix, nerves and blood vessels.