Epidermal structure of normal and regenerating skin of the agamine lizard Physignatus lesueurii (McCoy, 1878) with emphasis on the formation of the shedding layer

Comparative study of the epidermis of lepidosaurian reptiles helps us to understand the formation of the shedding complex which determines epidermal shedding. The present ultrastructural study has analyzed the complete sequence of epidermal differentiation in the agamine lizard Physignatus lesueurii from 1 to 80 days post-hatching. Beneath a beta-layer 20-40 layers of cells with an alpha-pattern of keratinization are produced, starting from narrow cells (mesos-like) followed gradually by typical thicker alpha-cells. At 80 days post-hatching an alpha-layer is still forming and the first epidermal shedding has still to take place. The differentiation of a shedding complex has been studied on the epidermis at 38 and 64 days of tail regeneration. Beneath the superficial regenerating (wound) epidermis, cells of the clear layer contain a meshwork of coarse and fibrous filaments which appear to turn into large keratohyalin-like granules. This extensive cytoskeleton may determine the progressive hardening of clear cells that function as a template for the formation of the large microomamentations of the underlying layer, a process that might be generalized for the genesis of microornamentations in all lepidosaurian reptiles. The microornamentations in Physignatus have a honey-comb pattern and are produced by the fusion between 'oberhautchen' and beta-cells. (C) 2000 Editions scientifiques et medicales Elsevier SAS.