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Amphibian Die Off: Chytrid Fungi

Amphibian Die Off: Chytrid FungiBio 102 Lab Case Study

Scanning electron micrograph of a frozen intact zoospore and sporangia of the chytrid fungus (Batrachochytrium dendrobatidis), CSIRO from Wikipedia

Image of Scanning Electron Micrograph of Chytrid Fungus by Dr. Alex Hyatt


Infectious disease of amphibian caused by Batrachochytrium dendrobatidis (Bd) (Daszak et al. 2003).First found in Australia in 1998 devastating amphibian populations (Berger et al. 1998)Specific to amphibiansOne of two species of chytrid known to infect vertebrates (Raphael and Pramuk, 2007)Other infects fishBd is spreading world wideResponsible for greatest disease induced biodiversity loss in recorded history (Skerratt et al. 2007)Extinction of over 200 species of frogsDead Bd-infected Atelopus limosus at Sierra Llorona (posed to show ventral lesions and chytridiomycosis signs), photo by Brian Gratwicke

Image of chytrid-infected frog by Brian Gratwicke

New species targets salamanders

Screenshot taken by Dr. Lynette HauserCC-BY3

Questions What phylum of fungi is responsible for chytridiomycosis?Why is this fungi successful at killing amphibians?Why be concerned about the worlds amphibian populations? What role do amphibians play in ecosystems?

Origin of BdNot exactly knownFound in Xenopus laevis which are used in labs, and previously were important for pregnancy testingInject frog with human female urine. If frog laid eggs a few hours later, human female was pregnant (Rogers, 2013)Also used in fishing as trade increased Weldon et al. (2004) found museum specimens with Bd dating back to 1938

Image of African Clawed Frog by H. Krisp

How might Bd be spreading through the environment?Propose a hypothesis that would explain why Bd is spreading like a new disease throughout the world

life cycle, asexual, Batrachochytrium dendrobatidis, Chytridiomycota by M. Piepenbring,_asexual,_Batrachochytrium_dendrobatidis,_Chytridiomycota_(M._Piepenbring).pngCC-BY-SA


How does Bd spread?Not exactly known, but likely human inducedPet trade, fishing trade, human consumption of bullfrogs, scientific trade (Reed et al. 2005, Weldon et al. 2004)Pico and Collins (2008)positive Bd water samples from bait shopsInadvertent through produce tradeOccurred in Tasmania in 1993 (Pauza and Driessen, 2008)Tree frog in a banana box in Tasmania imported from Australia was captured and developed Bd (Obendorf 2005)An estimated 50,000 frogs per year are accidentally carried in produce (McDonald and Speare 2000), and up to 70% are released at their destination (ODwyer et al., 2000)Tasmaniaassociated with gravel roads sprayed with water from wetlands, and moist soil transported (Pauza and Driessen, 2008)

Other scientists areindicating that Bdmay be spreadingdue to climatechange. How mightthis happen?

A chytrid-infected frog, Forrest Brem

Image of chytrid-infected frog by Forrest Brem

Climate Change and BdTemperatures warm, and organisms shift upward in elevation, or toward the poles, especially if ponds dry up (Parmesan, 2006)May introduce Bd to other areasIn Andes, deglaciationamphibians into new areas at record elevation, one species has Bd with no side effects, other species Bd and die offs (Seimon et al., 2006)

Figure 1. Summary of Red List categories for all amphibians. The percentage of species in each category is displayed on the pie chart (from Stuart et al. 2008)Some scientists are attempting to prevent the extinction of amphibians by capturing amphibians in the wild, breeding them in chytrid free labs, then releasing some of the amphibians into the wild. Discuss how such a strategy could save some species of amphibians.How else might we prevent the spread of Bd throughout the world?

The Amphibian Extinction Crisis - what will it take to put the action into the Amphibian Conservation Action Plan? By P. J. Bishop, A. Angulo, J. P. Lewis, R.D. Moore, G. B. Rabb and J. Garcia Moreno Commons License10

Works Cited Davidson, E. W., Parris, M., Collins, J. P., Longcore, J. E., Pessier, A. P., and Brunner, J. 2003. Pathogenicity and transmission of chytridiomycosis in tiger salamanders (Ambystoma tigrinum). Copeia 2003: 601-607.Berger, L., Speare, R., Daszak, P., Green, D. E., Cunningham, A. A., Goggin, C. L., Slocombe, R., Ragan, M. A., Hyatt, A. D., McDonald, K. R., Hines, H. B., Lips, K. R., Marantelli, G., and Parkes, H. 1998. Chytridiomycosis causes amphibian mortality associated with population declines in the rain forests of Australia and Central America. Proceedings of the National Academy of Sciences, USA. 95: 9031-9036.Raphael, B., and Pramuk, J. 2007. Treatment of chytrid infection in Typhlonectes spp. using elevated water temperatures. Proceedings of the IRCEB meeting, Phoenix, Arizona, November 2007. Unpublished.Skerratt, L. F., Berger, L., Speare, R., Cashins, S., McDonald, K. R., Phillott, A. D., Hines, H. B., and Kenyon, N. 2007. Spread of chytridiomycosis has caused the rapid global decline and extinction of frogs. EcoHealth 4: 125-134.Weldon, C. and du Preez, L.H. 2004. Decline of the Kihansi Spray Toad, from the Udzungwa Mountains, Tanzania. Froglog 62: 2-3.Weldon, C., du Preez, L. H., Hyatt, A. D., Muller, R., and Speare, R. 2004. Origin of the amphibian chytrid fungus. Emerging Infectious Diseases 10: 2100-2105Reed, K. D., Ruth, G. R., Meyer, J. A., and Shukla, S. K. 2005. Chlamydia pneumoniae infection in a breeding colony of African Clawed Frogs (Xenopus tropicalis). 2000. Emerging Infectious Diseases 6: 196-199.Picco, A. M., and Collins, J. P. 2008. Amphibian commerce as a likely source of pathogen pollution. Conservation Biology 22: 1582-1589.Obendorf, D. L. 2005. Developing field & diagnostic methods to survey for chytridiomycosis in Tasmanian frogs. Central North Field Naturalists, Inc. Tasmania, Australia. Report to the Department of Environment and Heritage, Canberra. Available online.O'Dwyer, W. T., Buttemer, W. A., and Priddel, D. M. 2000. Inadvertent translocation of amphibians in the shipment of agricultural produce into New South Wales: its extent and conservation implications. Pacific Conservation Biology 6:40-45.Pauza, M., and Driessen, M. 2008. Distribution and potential spread of amphibian chytrid fungus Batrachochytrium dendrobatidis in the Tasmanian Wilderness World Heritage Area. Report on Amphibian Chytrid Fungus in the TWWHA, Department of Primary Industries, Parks, Water, and Environment. Available online.Rogers, K. 2013. The First Pregnancy Tests and the Demise of Frogs.Encyclopedia Brittanica., T. A., Seimon, A., Daszak, P., Halloy, S. R. P., Schloegel, L. M., Aguilar, C. A., Sowell, P., Hyatt, A. D., Konecky, B., and Simmons, J. E. 2006. Upward range extension of Andean anurans and chytridiomycosis to extreme elevations in response to tropical deglaciation. Global Change Biology 12: 1-12.Parmesean, C. 2006. Ecological and Evolutionary Responses to Recent Climate Change. Annual Review of Ecology, Evolution, andSystematics 37:63769. Stuart, S.N. et al. (2008). Threatened Amphibians of the World. Barcelona/Gland/Arlington: Lynx Edicions/IUCN/Conservation International.