Fig. 3
From: Locally-curved geometry generates bending cracks in the African elephant skin
The epidermis of African elephants exhibits orthokeratosis and lacks keratohyalin granules. a, b Skin sections stained with haematoxylin and eosin from the top of a papillae (a) and from a trough (b). The lack of haematoxylin staining close to the transition from the viable epidermis to the stratum corneum (dashed lines) suggests that keratohyalin granules are not present in the animal’s epidermis (inset, public domain image: similarly stained human skin section shows, between dashed lines, the strong haematoxylin staining due to the presence of keratohyalin granules). Orthokeratosis is equally perceivable: the stratum corneum is thick but otherwise normal looking. Similar morphological features are often observed in human patients with ichthyosis vulgaris. The inset in Fig. 3a is an adaptation of the image created by Kilbad available in the public domain, sourced from https://en.wikipedia.org/wiki/File:Normal_Epidermis_and_Dermis_with_Intradermal_Nevus_10×.JPG. c, d Same as a, b, but only haematoxylin staining was applied for better contrast. Again, the absence of keratohyalin granules is clearly visible. The inset of c indicates that dark spots in the stratum corneum are not viable nuclei (N) but clusters of melanin granules (M). Scale bars: 100 μm
