Abstract
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.
Highlights
Climate warming and emerging infectious diseases (EIDs) are both major threats affecting biodiversity (Carey 2000, Harvell et al 2002, Thomas et al 2004)
Such environmental changes may lead to detrimental thermal and/or hydric conditions for organisms that prevent them from maintaining homeostasis with direct physiological and functional consequences (Spotila & Berman 1976, Shoemaker et al 1992, Spotila et al 1992)
EIDs can result from environmental changes in pathogen habitats, they can emerge in new geographical areas
Summary
Climate warming and emerging infectious diseases (EIDs) are both major threats affecting biodiversity (Carey 2000, Harvell et al 2002, Thomas et al 2004). Climate warming is expected to lead to greater contrasts in rainfall distributions, with longer and more intense drought periods (Solomon et al 2007) Such environmental changes may lead to detrimental thermal and/or hydric conditions for organisms (e.g. shelter loss, intense drought periods with reduced water availability) that prevent them from maintaining homeostasis (e.g. water and electrolyte equilibrium) with direct physiological and functional consequences (Spotila & Berman 1976, Shoemaker et al 1992, Spotila et al 1992). It is crucial to study these 2 threats to biodiversity in concert in order to understand their detrimental consequences In this context, our study focused on the impacts of both desiccation (as a potential consequence of climate warming) and exposure to an emergent pathogen in amphibians
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