A global problem requires a global multifaceted solution

Estrogen contamination increases vulnerability of amphibians to the deadly chytrid fungus

Aquatic contaminants and infectious diseases are among the major drivers of global amphibian declines. However, the interaction of these factors is poorly explored and could better explain the amphibian crisis. We exposed males and females of the Brazilian Cururu Toad, Rhinella icterica, to an environmentally relevant concentration of the estrogen 17-alpha-ethinylestradiol (an emerging contaminant) and to the chytrid infection (Batrachochytrium dendrobatidis), in their combined and isolated forms, and the ecotoxicity was determined by multiple biomarkers: cutaneous, hematological, cardiac, hepatic, and gonadal analysis. Our results showed that Cururu toads had many physiological alterations in response to the chytrid infection, including the appearance of cutaneous Langerhans's cells, increased blood leukocytes, increased heart contraction force and tachycardia, increased hepatic melanomacrophage cells, which in turn led to gonadal atrophy. The estrogen, in turn, increased the susceptibility of the toads to the chytrid infection (higher Bd loads) and maximized the deleterious effects of the pathogen: reducing leukocytes, decreasing the contraction force, and causing greater tachycardia, increasing hepatic melanomacrophage cells, and leading to greater gonadal atrophy, which were more extreme in females. The exposure to estrogen also revealed important toxicodynamic pathways of this toxicant, as shown by the immunosuppression of exposed animals, and the induction of the first stages of feminization in males, which corroborates that the synthetic estrogen acts as an endocrine disruptor. Such an intricate relationship is unprecedented and reinforces the importance of studying the serious consequences that multiple environmental stressors can cause to aquatic populations.

Lessons from practitioners for designing and implementing effective amphibian captive breeding programmes

With 40% of global amphibian species threatened with extinction, captive breeding programmes are an increasingly important conservation tool. The highest priority species occur in tropical countries, which presents a number of challenges. We conducted semi-structured interviews with 25 practitioners in Latin America, Africa and Asia to investigate how the effectiveness of amphibian captive breeding programmes could be improved. A thematic analysis identified 94 barriers and enablers across 13 themes. We found that existing programmes commonly followed a reactive and often ineffective four-stage operational model. Subsequently, we developed a proactive operational model, using the barriers and enablers identified by this study, to support programme managers in the implementation of effective programmes. Our findings suggest human dimensions are often critical barriers or enablers across all stages of captive breeding programmes. We recommend the development of strategic partnerships between institutions, including zoos, NGOs, governments and captive breeding programmes, to help overcome these critical barriers and improve the effectiveness of global amphibian conservation. This operational model could be translated to captive breeding programmes for other taxa.