Everyone knows the devastating effect that the chytrid fungus (Batrachochytrium dendrobatidis) has had on amphibian populations almost everywhere in the world–in 2009, it was estimated to infect at least 350 amphibian species on 6 continents.
A sad photograph of frogs killed by the chytrid fungus (image from the UC Riverside Center for Invasive Species Research website)
However, there has been some debate about how the fungus persists in environments–is it restricted to amphibian species, or can other taxa act as carriers or reservoirs? In a recent paper, Kilburn et al. (2011) find that five terrestrial reptiles, including Anolis humilis and Anolis lionotus and three snake species, carry fungal DNA in some form on their skin. The prevalence of fungal DNA on reptiles was correlated with its prevalence in anurans in different sites across Panama, and the intensity (i.e. amount of DNA) was generally lower in reptiles than amphibians. Combined with the absence of any symptoms of chytridiomycosis in the reptiles, these observations suggest a transfer of the fungus from the amphibians to the reptiles via their (often wet) habitats (the snakes might also consume infected frogs).
However, the authors caution that the lower prevalences and intensities do not necessarily mean an absence of infection, and it remains to be seen whether the chytrid fungus affects reptiles and if so, how severely. It is also unknown whether the fungus can complete it’s life cycle on a reptilian host. Either way, it seems possible that terrestrial reptiles play some role in maintaining high rates of fungal infection in amphibians.
Kilburn, VL, R Ibanez and DM Green. 2011. Reptiles as potential vectors and hosts of the amphibian pathogen Batrachochytrium dendrobatidis in Panama. Diseases of Aquatic Organisms 97: 127 – 134.
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Ramon E. Martínez-Grimaldo
which symptoms of this disease is present in reptiles like Anolis?
Ambika Kamath
Reptiles don’t actually show any symptoms–this paper just documents the presence of the fungus on the skin of these reptiles.
Jonathan Losos
I had drafted a post on this paper. Ambika did a better job than I would have, but I like the photo I had chosen better (Photo from http://forestwalkart.blogspot.com/2011/10/creepy-crawly-halloween-skulls-bones.html).
Incidentally, the authors of the paper state, somewhat provocatively, “Reasoning, though, that chytridiomycosis was strictly a disease of amphibians, Whitfield et al. (2007), Wake (2007) and Sinervo et al. (2010) attributed declines in reptile abundance in Central America, in general, to the effects of climate change. We cannot conclude from our results that B. dendrobatidis is a virulent reptile pathogen, or that it causes disease-induced decline in reptile populations, but our evidence that reptiles do carry B. dendrobatidis DNA in neotropical localities where both reptiles and amphibians have declined warrants some concern.”