Introduction
Kingdom: Fungi
Division: Chytridiomycota Class: Chytridiomycetes Order: Rhizophydiales Genus: Batrachochytrium Species: B. dendrobatidis |
Batrachochytrium dendrobatidis (Bd for short) is a deadly chytrid that infects and causes chytridiomycosis in frogs and other amphibians[4]. As a chytrid, Bd spores are flagellated (zoospores) and are typically aquatic[7]. Bd is one of only two chytrids known to infect vertebrates, and itself is able to infect over 350 species. It has been found on every continent besides antartica, and is thought to be a highly important factor in amphibian declines[1, p713][6][7].
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Zoospore
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Life Cycle & Chytridiomycosis
A typical Bd life cycle lasts 4 to 5 days. Starting from the point of view of a rogue zoospore, it swims until it finds a suitable amphibian host, and infiltrates through the skin. The zoospore develops into a thallus ('body'), which burrows in and anchors via rhizoids. The rhizoids may also play a role in secreting enzymes and absorbing nutrients from the skin of the organism. The thallus then produces one or many zoosporangium, which grow towards the surface of the skin, and once the contained zoospores are mature, release them into the water surrounding the amphibian[5].
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A (generic) thallus
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After infecting an amphibian, Bd kills by disrupting electrolyte transport in the skin so badly that cardiac arrest ensues. Around 10,000 zoospores was found to be the threshold fatal to frogs (of Rana muscosa) and salamanders (Pseudoeurycea leprosa and Bolitoglossa rufescens)[5]. As of yet it's unknown if fungal toxins play a role in chytridiomycosis, or if impairment to the amphibians functions is due to physical damage to their skin cells[5].
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References
[1]Campbell & Reece, Biology, 8th Edition
[4]GAHL, M. K., LONGCORE, J. E., & HOULAHAN, J. E. (2012). Varying Responses of Northeastern North American Amphibians to the Chytrid Pathogen Batrachochytrium dendrobatidis. Conservation Biology, 26(1), 135-141. doi:10.1111/j.1523-1739.2011.01801.x
[5]http://www.amphibiaweb.org/chytrid/chytridiomycosis.html
[6]http://oh93independentstudyonfungi.blogspot.com/2013/11/chytrids.html
[7]http://eol.org/pages/998631/overview
[4]GAHL, M. K., LONGCORE, J. E., & HOULAHAN, J. E. (2012). Varying Responses of Northeastern North American Amphibians to the Chytrid Pathogen Batrachochytrium dendrobatidis. Conservation Biology, 26(1), 135-141. doi:10.1111/j.1523-1739.2011.01801.x
[5]http://www.amphibiaweb.org/chytrid/chytridiomycosis.html
[6]http://oh93independentstudyonfungi.blogspot.com/2013/11/chytrids.html
[7]http://eol.org/pages/998631/overview