Fig. 5

Ultrastructural analyses of zebrafish caudal fins by TEM. (A–C) Wild-type (WT) fin sections showing the structural organization of the fin tip. (A) In a proximal section, the lepidotrichia hemirays were stained dark (arrows) and actinotrichia are large bundles located inside near the hemirays (asterisks). A single artery can be seen in the center of the fin ray (arrowhead). (B) In a medial section, actinotrichial bundles were prominent (asterisks), but lepidotrichia were thin (arrow, only one side of the lepidotrichia is shown in this section). (C) In a distal section, the fin was much thinner and consisted of only the outer layers of the epidermis (arrowheads), numerous actinotrichia bundles (asterisks), and a one-cell layer of the mesenchyme (arrow). (D–F) Sections of a prp fin tip. (D) In a proximal section, the lepidotrichia hemirays are visible (arrows), but the actinotrichia were not present. Also in this section, two vessels can be observed in the intra-ray compartment (arrowheads) reflecting the plexus phenotype of prp. (E) In a medial section, actinotrichial bundles are visible but much smaller at almost the size of dots (arrows). Interestingly, the mesenchymal compartment was thicker in prp (double-headed arrow). (C) In a distal section, the actinotrichia were again small, and the intra-ray mesenchymal compartment was thick in prp. Note that one cannot directly compare the sizes of actinotrichia in (E) and (F) because they are of different magnifications.