1. Batrachochytrium dendrobatidis Amphibian Chytrid Fungus
Daniel Gillespie
Bio 594: Mycology
Fall 2013

2. Overview B. dendrobatidis (Bd) Chytridiomycosis Going Forward
Classification
Physiology
Origin & Global Dissemination
Chytridiomycosis
Effect
Notable Amphibians
Population Declines
Going Forward

3. Phylum: Chytridiomycota
Classification
Phylum: Chytridiomycota
Class: Chytridiomycetes
Order: Rhizophydiales
Family: Incertae sedis

4. Naming 1999, Longcore et al., Mycologia
Name derived from blue poison dart frog, Dendrobates azureus
Infected specimens from National Zoo in D.C.

5. Description Bd infects the skin of amphibians
It grows into a monocentric or colonial thallus
Immature sporangia develop in the deeper layers
Bd growth in skin of blue poison dart frog

6. Description
Sporangia push outward to eject zoospores into the environment
Discharge tubes develop
Zoospores spherical with flagellum
In lab only swam about 2 cm before encysting
Bd zoospore on agar surface

7. Description Growth in wide range of conditions
Optimal growth 17 – 25 ºC
Above 25º growth slows
Sexual reproduction has not been successful in labs
May result in thick-walled, resistant sporangia

8. Origin Weldon et al. 2004 , Emerging Infectious Diseases
Studied museum specimens from around the world
First positive: 1938, South Africa
First positive outside Africa: 1961, Quebec
Primary host: Xenopus laevis
Xenopus laevis

9. Dissemination X. laevis spread began in 1930s worldwide
Pregnancy assay
Pet trade
Since, other vectors have been suggested

10. Chytridiomycosis Infects skin of frogs 2 hypotheses on death of frogs:
Outer layers – stratum corneum and stratum granulosum
2 hypotheses on death of frogs:
Inhibition of skin function
Excretion of proteolytic enzymes
Growth results in hyperkeratosis
Lesions often form in area of infection

11. Notable Amphibians
Several species do not show clinical signs of infection
X. laevis produces antimicrobial peptides in skin
Peptides act as barrier
Frogs also showed immune system
responses fighting Bd growth

12. Frog Declines Since 1980 Many areas experiencing wavelike declines
435 frog species declining
233 attributed to habitat loss and exploitation
Many areas experiencing wavelike declines
Areas of significant impact include Australia and So. America

13. Map of Spread

14. Going Forward Why Care? Biodiversity Importance as Indicator Species
Approximately 7,000 species
New species discovered constantly
Importance as Indicator Species
Sensitive to environment
Abundant in wetland habitats
Oreophryne gagneorum, discovered in September 2013 in Papa New Guinea

15. Going Forward What can we do? Research Bd genome recently sequenced
Frogs are hard to find
Current research is limited
Bd genome recently sequenced
Focus on population effects and possible cure needed

16. References
Berger, L., Hyatt, A. D., Speare, R., & Longcore, J. E. (2005). Life cycle stages of the amphibian chytrid Batrachochytrium dendrobatidis. Diseases of aquatic organisms, 68,
Berger, L., Speare, R., Hines, H. B., Marantelli, G., Hyatt, A. D., McDonald, K. R., ... & Tyler, M. J. (2004). Effect of season and temperature on mortality in amphibians due to chytridiomycosis. Australian Veterinary Journal, 82(7),
Berger L, Speare R, Hyatt A (1999) Chytrid fungi and amphibian declines: overview, implications and future directions. In: Campbell A (ed) Declines and disappearances of Australian frogs. Environment Australia, Canberra, p 23–33
Johnson, M. L., & Speare, R. (2005). Possible modes of dissemination of the amphibian chytrid Batrachochytrium dendrobatidis in the environment. Diseases of aquatic organisms, 65,
Kilpatrick, A. M., Briggs, C. J., & Daszak, P. (2010). The ecology and impact of chytridiomycosis: an emerging disease of amphibians. Trends in Ecology & Evolution, 25(2),
Kriger, K. M., & Hero, J. M. (2007). The chytrid fungus Batrachochytrium dendrobatidis is non‐randomly distributed across amphibian breeding habitats.Diversity and Distributions, 13(6),
Longcore, J. E., Pessier, A. P., & Nichols, D. K. (1999). Batrachochytrium dendrobatidis gen. et sp. nov., a chytrid pathogenic to amphibians. Mycologia,
Morgan, J. A., Vredenburg, V. T., Rachowicz, L. J., Knapp, R. A., Stice, M. J., Tunstall, T., ... & Taylor, J. W. (2007). Population genetics of the frog-killing fungus Batrachochytrium dendrobatidis. Proceedings of the National Academy of Sciences, 104(34),
Orchard, S. A. (1999). The Gordian knots of the international declining amphibian populations task force (DAPTF). In: Campbell A (ed) Declines and disappearances of Australian frogs. Environment Australia, Canberra, p 9-13
Piotrowski, J. S., Annis, S. L., & Longcore, J. E. (2004). Physiology of Batrachochytrium dendrobatidis, a chytrid pathogen of amphibians. Mycologia,96(1), 9-15.
Ramsey, J. P., Reinert, L. K., Harper, L. K., Woodhams, D. C., & Rollins-Smith, L. A. (2010). Immune defenses against Batrachochytrium dendrobatidis, a fungus linked to global amphibian declines, in the South African clawed frog, Xenopus laevis. Infection and immunity, 78(9),
Rosenblum, E. B., James, T. Y., Zamudio, K. R., Poorten, T. J., Ilut, D., Rodriguez, D., ... & Stajich, J. E. (2013). Complex history of the amphibian-killing chytrid fungus revealed with genome resequencing data. Proceedings of the National Academy of Sciences, 110(23),
Skerratt, L. F., Berger, L., Speare, R., Cashins, S., McDonald, K. R., Phillott, A. D., ... & Kenyon, N. (2007). Spread of chytridiomycosis has caused the rapid global decline and extinction of frogs. EcoHealth, 4(2),
Stuart, S. N., Chanson, J. S., Cox, N. A., Young, B. E., Rodrigues, A. S., Fischman, D. L., & Waller, R. W. (2004). Status and trends of amphibian declines and extinctions worldwide. Science, 306(5702),
Weldon, C., du Preez, L. H., Hyatt, A. D., Muller, R., & Speare, R. (2004). Origin of the amphibian chytrid fungus. Emerging infectious diseases, 10(12), 2100.
Welsh Jr, H. H., & Ollivier, L. M. (1998). Stream amphibians as indicators of ecosystem stress: a case study from California's redwoods. Ecological Applications, 8(4),

17. Links to Photos http://www.amphibianark.org/the-crisis/chytrid-fungus/
Longcore, J. E., Pessier, A. P., & Nichols, D. K. (1999). Batrachochytrium dendrobatidis gen. et sp. nov., a chytrid pathogenic to amphibians. Mycologia,