The Temperature Relationship of Batrachochytrium dendrobatidis

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Introduction

Composite line drawing of a longitudinal section of a Batrachochytrium dendrobatidis zoospore.[1]

By [Eva Brazer]


Amphibian species around the world are experiencing unprecedented population decline due to the emerging infectious disease chytridiomycosis, which is caused by the chytrid fungus Batrachochytrium dendrobatidis (Bd)[2]. The chytrid pathogen is considered an emerging infectious disease because it was discovered and described only in the last twenty years[3], and has continued to spread globally causing devastating effects[4]. Batrachochytrium dendrobatidis has been identified on every continent on which amphibians are present[2].


Recent global mapping initiatives reported that Batrachochytrium dendrobatidis had been identified as having infected 1,015 of the 1,854 species examined (54%). Further population analysis found that the fungus has resulted in the decline of at least 501 species (6.5% of all amphibian species), with 124 experiencing a decrease in the species population of over 90%[5]. Over a hundred presumed extinctions have been attributed to chytridiomycosis[6]. The catastrophic impact of Batrachochytrium dendrobatidis is so significant that it is believed to be the largest threat to the biodiversity of any class of vertebrate[2]. Batrachochytrium dendrobatidis has been documented in hundreds of amphibian species, and reports of infection in new species and geographic locations are continually increasing[6].


Climate change models are predicting an increase in the frequency and magnitude of temperature fluctuations[7]. This has caused concern that these temperature fluctuations may lead to increased pathogen development, transmission, and ectotherm-host susceptibility[8]. The parasitic performance of Batrachochytrium dendrobatidis is sensitive to temperature[8]. By examining the relationship between pathogen and host interactions particularly in relation to temperature fluctuations, scientists can better predict and mitigate the spread of Batrachochytrium dendrobatidis to new amphibian populations.

Phylogeny

Phylogeny and classification of the genus Batrachochytrium. Cladogram showing the taxonomic position of Batrachochytrium dendrobatidis and Batrachochytrium salamandrivorans within the fungal kingdom (a), the phylum Chytridiomycota (b) and order of the Rhizophydiales (c). [9]


Scientific classification

Kingdom: Fungi
Division: Chytridiomycota
Class: Chytridiomycetes
Order: Rhizophydiales
Genus: Batrachochytrium
Species: B. dendrobatidis


Effect on Amphibians

Effect of Temperature

Life Cycle

Life cycle of the pathogenic chytrid fungus Batrachochytrium dendrobatidis. [6]


Effect of Temperature

Geographic Distribution

Geographic distribution of Batrachochytrium species, Bd and Bsal[10]


Genotypes of Bd isolated from infected amphibians in the international trade and phylogenetically linked genotypes from segregated geographic localities.[11]


Effect of Temperature

Climate Change

Conclusion

References

  1. Berger et al. 2005. Life cycle stages of the amphibian chytrid Batrachochytrium dendrobatidis. Inter-Research. 68:52-63
  2. 2.0 2.1 2.2 Weldon et al. 2004. Origin of the Amphibian Chytrid Fungus. Emerging Infectious Diseases. 10(12):2100-2105
  3. Berger et al. 1998. Chytridiomycosis causes amphibian mortality associated with population declines in the rain forests of Australia and Central America. PNAS. 95:9031-9036
  4. Piotrowski et al. 2004. Physiology of Batrachochytrium dendrobatidis, a Chytrid Pathogen of Amphibians. Mycologia. 96:9-15
  5. Fisher, M.C., T.W.J. Garner. 2020. Chytrid fungi and global amphibian declines. Nature Reviews Microbiology. (1740-1526).
  6. 6.0 6.1 6.2 Rosenblum et al. 2010. The Deadly Chytrid Fungus: A Story of an Emerging Pathogen. PLoS Pathogens. 6(1):e1000550
  7. Bradley et al. 2019. Shifts in temperature influence how Batrachochytrium dendrobatidis infects amphibian larvae. Health and Medicine. 14:(9)
  8. 8.0 8.1 Stevenson et al. 2013. Variation in Thermal Performance of a Widespread Pathogen, the Amphibian Chytrid Fungus Batrachochytrium dendrobatidis. PLoS ONE. 8(9):e73830
  9. Rooij et al. 2015. Amphibian chytridiomycosis: A review with focus on fungus-host interactions. Veterinary Research. 46(1):137.
  10. Bower et al. 2017. Amphibians on the brink: Preemptive policies can protect amphibians from devastating fungal diseases. Science. 357:454-455
  11. O’Hanlon et al. 2018. Recent Asian origin of chytrid fungi causing global amphibian declines. Science. 360:621-627



Authored for BIOL 238 Microbiology, taught by Joan Slonczewski, 2018, Kenyon College.