Years of research and laborious experiments in the field and the laboratory can be resumed in short scientific publications like the paper that we have just published in the journal Diseases of Aquatic Organism.
To understand the dynamic of the disease in the whole amphibian community, it is necessary to know the response to every one of the different present species and their importance in the infection transmission. Ultimately, this is vital to design management strategies that minimize the outbreaks and improve the reintroduction programs. Luckily, the rich amphibian community of Peñalara Mountains has allowed us to develop a series of experiments aimed at this purpose.
In a first experiment, we studied if the midwife toad’s larvae act like “amplifiers” of the infection, that is to say, making it to be more intense or incrementing the prevalence in other species that they live with. In order to do that, we installed a floating raft in the Laguna Grande of Peñalara, with different drilled recipients to allow the entry of the lake's water and where midwife toad's larvae where put in different densities. It turns out that even though the common toad’s larvae did get infected, even in absence of the ones from the midwife (that is to say, through the fungus’ zoospores present in the lake without any direct contact with an infected amphibian), the common toad’s larvae got more infected when they were put with the midwife toad’s larvae, making clear the “amplifying” role of the infection of these species.
In a second experiment, also in the Laguna Grande, we investigated if the different amphibian species in Peñalara differ in the probability and the intensity of their infection when they are in contact with midwife toad’s larvae. Even though we did not find great differences between the different species, it is important to point out that this experiment refers only to the year's larvae, while the species with overwintering larvae do present higher infection loads and probabilities.
In the last experiment, this one in the laboratory, we studied, in addition to the response of the rest of the species to the presence of infected midwife toad's larvae, the differences in the development of the infection of these last ones, depending on the species that they are living with. That way we could check that the midwife toad’s larvae, when isolated from other species, had lower levels of infection that those that were put with other host; which points out that the other species do also amplify the infection to the midwife toad’s larvae, although to lesser extent.
Even though it can be difficult to understand at first sight how these results can help us to fight against the fungus, the truth is that the detailed knowledge of the disease dynamic in the whole community it is being of great help for us to design new mitigation strategies based in the retirement or in the control of concrete species.
Translated by Maialen Iriso