Hepatic fibrosis induced zinc-deficient dermatosis in American alligators (Alligator mississippiensis)

Crocodilian farming generates strong economic incentives for the conservation of several species previously endangered by intensive hunting. Ranching farms, in particular, are intimately connected to the natural crocodilian habitat and have a significant impact on wetland preservation. The financial sustainability of this industry relies on the production of first grade skins for the luxury leather market. Only flawless skins are considered of first grade by the stringent standards of the market, and even a single defect represents an economical loss. "Double scale" is one such defect that drastically reduces the appeal of crocodilian skin. Although double scale defects represent a threat to the economical sustainability of the farming industry, there is no scientific literature available on this topic. This study, carried out in a ranching farm of American alligators (Alligator mississippiensis), represents the first investigation into the pathogenesis of double scale. Our results indicate that double scale is a keratinization disorder associated with zinc deficiency. Furthermore, we found that portal hypertension due to liver fibrosis, underlies zinc deficiency in cases of double scale. Lastly, we found that chronic vitamin A toxicity can cause liver fibrosis in crocodilians. For the first time, we demonstrate a causal association between liver disease and skin quality in a crocodilian species. This study reveals the conserved role of zinc in the homeostasis of reptilian skin. Also, we show that, like mammals, reptiles may develop liver fibrosis following chronic vitamin A toxicity and through activation of hepatic stellate cells. Our results advance herpetological medicine and will translate into improved captive crocodilian welfare and husbandry.