A histological study of emu (Dromaius novaehollandiae) skin

The skin of the emu Dromaius novaehollandiae is described in its entirety by light microscopy for the first time, therefore providing a basis for comparison with the integument of volant birds. The epidermal and dermal layers have a similar arrangement to other avian species. The concentration of lipid spheres in the basal layer of the epidermis is unique to emus. Although no differences in collagen density with depth of the dermis were observed, collagen bundle diameter is significantly smaller in the stratum superficiale compared to the stratum compactum (P = 0.001). The extensive stratum laxum, comprised predominantly of adipose tissue, may be an evolutionary adaptation to support the large feathers and also enhance insulation against ambient subzero temperatures. Males have a significantly thicker cellular epidermis (P = 0.024) and stratum compactum (P = 0.04) than females. In contrast, females have denser collagen (P = 0.04) within the stratum superficiale and stratum compactum.