DANIEL GILLESPIEBIO 594 : MYCOLOGY

FALL 2013

Batrachochytrium dendrobatidis

Amphibian Chytrid Fungus

Overview

B. dendrobatidis (Bd) Classification Physiology Origin & Global Dissemination

Chytridiomycosis Effect Notable Amphibians Population Declines

Going Forward

Classification

Phylum: Chytridiomycota

Class: Chytridiomycetes

Order: Rhizophydiales

Family: Incertae sedis

Naming

1999, Longcore et al., Mycologia

Name derived from blue poison dart frog, Dendrobates azureus

Infected specimens from National Zoo in D.C.

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

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

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

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 laevisXenopus laevis

Dissemination

X. laevis spread began in 1930s worldwide Pregnancy assay Pet trade

Since, other vectors have been suggested

Chytridiomycosis

Infects skin 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

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

Frog Declines

Since 1980 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

Map of Spread

Going Forward

Why Care?

Biodiversity 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

Going Forward

What can we do?

Research Frogs are hard to find Current research is limited

Bd genome recently sequenced

Focus on population effects and possible cure needed

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, 51-63.

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), 434-439.

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, 181-186.

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), 109-118.

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), 781-788.

Longcore, J. E., Pessier, A. P., & Nichols, D. K. (1999). Batrachochytrium dendrobatidis gen. et sp. nov., a chytrid pathogenic to amphibians. Mycologia, 219-227.

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), 13845-13850.

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), 3981-3992.

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), 9385-9390.

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), 125-134.

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), 1783-1786.

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), 1118-1132.

Links to Photos

1. http://www.amphibianark.org/the-crisis/chytrid-fungus/2. http://www.arkive.org/dyeing-poison-frog/dendrobates-tinctorius/image-G15404.html3. http://www.arkive.org/dyeing-poison-frog/dendrobates-tinctorius/image-G104487.html4. Longcore, J. E., Pessier, A. P., & Nichols, D. K. (1999). Batrachochytrium dendrobatidis gen. et sp.

nov., a chytrid pathogenic to amphibians. Mycologia, 219-2275. Longcore, J. E., Pessier, A. P., & Nichols, D. K. (1999). Batrachochytrium dendrobatidis gen. et sp.

nov., a chytrid pathogenic to amphibians. Mycologia, 219-2276. http://upload.wikimedia.org/wikipedia/commons/b/b4/Xenopus_laevis_02.jpg7. http://www.fcps.edu/islandcreekes/ecology/Amphibians/Bullfrog/bull2.jpg8. http://www.xenopus.com/box_of_frogs.jpg9. http://mongabay-images.s3.amazonaws.com/13/0918fungus1.jpg10. http://www.earthfiles.com/Images/news/A/AmphibianAfricanClawedFrogLo.jpg11. http://cdn4.sci-news.com/images/2013/09/image_1400_3-Oreophryne.jpg