Frogs and Microbes

By Greg Ruthig, Ph.D.

I have been interested in amphibians for as long as I can remember. Growing up in upstate New York, I enjoyed finding bright orange red efts in the woods and searching for hours to find spring peepers in the midst of deafening choruses. Although I always knew amphibians were important consumers of insects, which is a comforting thought when wading through a wetland being bitten by mosquitoes, I never appreciated the even smaller organisms whose lives are affected by amphibians and who can have enormous effects on amphibians themselves.

My research is focused on aquatic microbes that are found on amphibians. One group of organisms I study are called watermolds, which are fungus like organisms that consume dead amphibians and can sometimes be pathogens of their eggs. Another microbe that I study, which has received much more attention is the chytrid fungus, Batrachochytrium dendrobatidis. This fungus infects the skin of adult amphibians and the mouths of many tadpoles and has been associated with amphibian declines and extinctions around the world. I am interested in determining how this pathogen is able to drive its amphibian hosts to extinction and how its persistence in the environment, even after many of its host disappear, affects attempts to reintroduce amphibians back into their native environments.

Although microbes are receiving most of their attention due to the fact that they are pathogens, many mirco-organisms interact with amphibians in other ways. Watermold often act saprophytically on amphibians, meaning that they only consume their hosts after they have already died from other causes. Reid Harris at James Madison University and others are now discovering that many of microbes are actually helpful to amphibians, because they can inhibit pathogens. To appreciate how many microbe species are associated with amphibians, I recommend looking at the skin of an amphibian under a microscope or even a hand lens. You will find that it is moving with all kinds or microbes, whose ecological associations with amphibians remain mostly unknown.

As amphibian populations decline, I think about how their losses will affect both large and very small organisms. An amphibian body is an ecosystem within itself and we are just beginning to understand its complexities. Conserving amphibians will impact many more species than the frogs and salamanders that capture our attention when we are children.