Impact of both desiccation and exposure to an emergent skin pathogen on transepidermal water exchange in the palmate newt Lissotriton helveticus .

Amphibians are the vertebrate group most affected by global change. Their highly permeable skin is involved in maintaining homeostasis (e.g. water and electrolyte equilibrium), which makes them particularly vulnerable to climate warming and skin pathogens. This study focused on the impacts of both desiccation (as a potential consequence of climate warming) and exposure to Batrachochytrium dendrobatidis (Bd), an emergent skin pathogen of amphibians. Bd causes chytridiomycosis, a lethal skin disease of amphibians, and is responsible for mass mortality events in several regions of the world. Because Bd colonizes the superficial layers of the epidermis, it is assumed to affect water transfer across the skin. We investigated the behavioural postures of the palmate newt Lissotriton helveticus expressed in response to desiccation and their influence on transepidermal water loss (TEWL) rate. We also investigated the effects of repeated 24 h exposure to Bd (i.e. every 4 d for 16 d) on the TEWL and ventral water absorption (VWA) rates of these newts. Our results suggest an efficient behavioural water-conserving mechanism, i.e. an 'S'-shaped posture associated with a restricted activity rate, not affected by repeated exposure to Bd. Similarly, TEWL was not significantly affected in exposed newts. VWA was significantly reduced after just 24 h exposure to Bd without modification until the end of the experiments. Our results suggest that Bd could rapidly inhibit rehydration of L. helveticus through fungal toxins and disrupt an essential function for survival.