Figure 4

Innervation patterns of integumentary sensory organs in crocodylians. Macro-photographs of the Nile crocodile trunk (A) and head (B), and spectacled Caiman head (C). Lower panels show parasagittal sections of the corresponding integumentary sensory organs (ISOs) processed for immunostaining of various neuronal markers: neuron-specific enolase (NSE), growth-associated protein 43 (GAP43), neuron cytoplasmic protein gene product 9.5 (PGP9.5), neuropeptide Y (NPY), neurofilament, heavy polypeptide (NEFH), neuron-specific nuclear protein (NEUN), somatostatin (SST), or substance P (SP). Cell nuclei were counterstained with 4',6-diamidino-2-phenylindole (blue). The epidermal-dermal junction is indicated by dashed lines. Magnification bars, 100 μm. (D) Semiquantitative reverse transcription-PCR analysis of genes (names indicated on the left), encoding transduction channels with different sensory modalities (vertical black rectangles), in Nile crocodile and spectacled caiman ISO-bearing skin tissues from different body parts (Ja, jaws; Do, dorsum; Ve, ventrum; Ne, neck; To, tongue). The embryonic brain (Br) of crocodylian species was used as a positive control for gene expression. Blue dashed rectangles indicate differential expression of Trpa1 and Trpm8 in Nile crocodile and spectacled caiman. (E) Parasagittal cryosections of ISOs stained using whole-mount in situ hybridization with probes targeting various ion channel genes (indicated on the corresponding panel) on embryonic Nile crocodile heads at E45 (small insets). The epidermal-dermal junction is indicated by dashed lines. Magnification bars: 100 μm.