Fig. 5. Presumed mesodermal portions of dorsal lip explants make taste buds, whereas isolated endodermal components do not. (A) Small endodermal dorsal lip explants (Endo30s) persist as round balls of cells through to hatchling stages. (B) Cryosections of Endo30 explants were devoid of CR-IR; neither CR-IR taste buds nor solitary CR-IR cells were evident. However, yolk granules, indicative of endodermal tissue, autofluoresce in the green channel. Nuclei are stained with Hoechst (blue). (C) Mesodermal explants undergo substantial morphogenesis, and possess melanin granules typical of ectoderm (arrows). (D) Taste buds with numerous fusiform, CR-IR cells (green, * marks apical region of each taste bud) are present in this section of a mesodermal dorsal lip explant counterstained with Hoechst (blue). Parvalbumin-IR muscle (red-mu) is also present in this section. (E) The taste bud on the right in D is shown at higher magnification to illustrate the fusiform nature of CR-IR (green) cells within the bud, as well as the characteristic apical processes of these cells (*). (F) A few solitary, irregularly shaped, CR-IR cells (green) are shown in this cryosection of an Endo50 endodermal dorsal lip explant counterstained with Hoechst (blue). This explant did not develop taste buds, however. Scale bars: 100 µm in B; 50 µm in D,F; 25 µm in E.