Investigación Sociedad zoológica de Londres (ZSL)

• Saving the last mouth breeding frogs: is chytridiomycosis driving Darwin’s frogs extinction? Sociedad zoológica de Londres (ZSL).

Investigador principal: Claudio Soto-Azat

Resumen de la investigación

Darwin’s frogs are two species (Rhinoderma rufum and R. darwinii), that inhabit the temperate southern beech forest of Central and South Chile. Rhinoderma darwinii was named in honour of Charles Darwin, who found this frog during his epic voyage on the H.M.S. Beagle in the 1830s, and R. rufum was recognised as a distinct species in 1902. The behaviour that sets these frogs apart from all other amphibians is that the males care for their young by incubating them in their vocal sacs for part of their development. There has been no sign of R. rufum since 1980, while R. darwinii has undergone a clear population decline.

The reasons for this apparent disappearance remain poorly understood. Along all the historical distribution of R. rufum and within the northern range of R. darwinii there has been great impact trough habitat degradation for pine industrial plantations and for agricultural activities. Although, these can explain the long term decline of both species, these fails to elucidate the mysterious disappearing of R. rufum from all its historical range, a species which seemed to be relatively abundant prior to the 1970’s.

Also do not explain successfully the strange and abrupt decline of R. rufum and R. darwinii from National parks and were native reluctant forest pockets remains, and therefore forestry industry have not developed. In this context, amphibian chytridiomycosis caused by the nonhyphal zoosporic chytrid fungus Batrachochytrium dendrobatidis (Bd) is recognized as an emerging infectious disease, already described in over 200 species of anurans and caudates from all continents and has been associated with the current global amphibian decline and extinction crisis.

The scientific evidence indicates the pathogen has been recently introduced into new regions from an area of enzootic infection and that the international commerce of amphibians (for food, laboratories, pets and zoo animal collections) as well as introduction of some anurans species has been involved in the widespread of the disease. Within South America infection has been demonstrated in anurans from Venezuela, Colombia, Ecuador, Peru, Brazil and Argentina.

In Chile non-published investigations suggest the presence of the fungi in the northern, central and south Chile, infecting species such as the widely spread invasive African clawed frog (Xenopus laevis) and northern populations of R. darwinii. Chilean anurans comprise 51 species, characterized by a high degree of endemism. Of these, 19 are considered EDGE species, with four within the top 50 species: Bullock’s false toad (Telmatobufo bullocki, EDGE #4), Barrio’s frog (Insuetophrynus acarpicus, EDGE #23), Chile mountains false toad (Telmatobufo venustus, EDGE #30), and Chile Darwin’s frog (Rhinoderma rufum, EDGE #45).

Using a non-invasive sampling, based on skin swabbing and posterior quantitative real-time PCR TaqMan assay (qPCR), from 600 individuals, from 26 different amphibian species, including 14 species threatened by extinction, will be assessed for the presence of Bd. At the same time, the infection will be assessed in 200 individuals of X. laevis, trough qPCR and histopathological techniques.

There is a special concern to demonstrate how a species introduction, together with a “natural” pathogen, may become a significant threat to biodiversity, especially when a disease is introduced to susceptible populations which never have been in contact with the pathogen.

This project tries to evaluate the presence and impacts of chytridiomicosis in Chilean native amphibians, with special concern to evaluate susceptibility of R. darwinii to the disease and identification of affected populations. On the other hand search for the critically endangered R. rufum, started by the author in collaboration with scientist from ZSL in 2007, will continue along its historical range, together with sampling of sympatric anurans, in order to elucidate the presence of Bd in this area.

Along this, work with scientists, zoo conservation departments, government authorities, and local people started also in 2007, will continue to ensure a multidisciplinary approach of the conservation of Darwin´s frogs.