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Background Information

Amphibians in Trouble

Amphibians are disappearing around the world. A systematic global assessment of all 5,743 known amphibian species found that one-third of all species surveyed, and 42% of all non data-deficient species, are in danger of extinction1. This proportion is much higher than any other assessed class of vertebrates, including birds (13%) or mammals (26%) 2. What is particularly alarming to conservationists is that 122 species are believed to have gone extinct since 1980, compared to just five bird species and no mammals during the same time period 1. This unprecedented rate of species loss deserves an unprecedented global response.

A Deadly Disease

Enigmatic amphibian declines’ have been widely discussed since the 1980s as researchers documented inexplicable crashes in populations of montane amphibians in the USA 3, Australia 4, Central America 5 and South America 6. Smithsonian scientist Bill Laurence first speculated in 1996 that a disease may be responsible for these ‘enigmatic declines’ 7, a hypothesis that researcher Lee Berger and colleagues verified shortly thereafter by confirming the presence of Batrachochytrium dendrobatidis (Bd) associated with an amphibian mortality event 8.

In 1999, scientists at the Smithsonian’s National Zoological Park (NZP) and the University of Maine described the novel pathogen Bd while demonstrating that the novel organism was indeed a deadly amphibian disease agent 9. This discovery changed the way in which scientists and conservationists viewed amphibian declines, and many of the historic species disappearances are now being re-examined and attributed to the Bd epidemic. Bd is believed to be responsible for the disappearance and probable extinction of more than 70 species of Harlequin frogs in Central and South America 10, both known species of Gastric Brooding Frog in Australia 7, the Monte Verde Golden Toad of Costa Rica 10, the Golden Coqui Frog of Puerto Rico 11 and the Wyoming Toad in North America 12 and possibly hundreds of other species.

More recent investigations by Smithsonian Associate Karen Lips and colleagues have documented the wave-like spread of this pathogen throughout the montane regions of Central and South America 5. When, as predicted, Bd arrived at El Copé, Panama, in late 2004, frog species from all seven extant families started dying. Within 5 months, 50% of the species present had been extirpated,and the remainder persisted at populations only 20% of their pre-infection abundance 13. The fungus continued its eastward spread and arrived in the El Valle region of Panama, about 35 km west of El Copé, in late 2006. Here, conservationists associated with the Houston Zoo began capturing and housing species in a quarantined, managed care situation that provided protection from Bd exposure 14. Today, this small center at the El Nispero Zoo in Panama is at capacity, housing 50 amphibian species, 17 of which are extinct or facing extinction in the wild.

Eastern Panama is our Last Chance

Biologists had hoped that the low lying Panama Canal region would serve as a natural barrier to Bd spread. However, by 2008, Bd was found for the first time east of the canal in the Soberania National Park (surrounding the town of Gamboa). All evidence suggests that the pathogen will continue its eastward march at a rate of 30 km per year towards the mountainous Darien Region, a remote, poorly explored area serving as habitat for the last intact amphibian fauna in Central America15. Eastern Panama is known to contain at least 121 amphibian species (61% of all the amphibian fauna of Panama) and to be a stronghold for at least 50 to 60 species listed as ‘critically endangered’, ‘endangered’ or ‘data deficient’ by the IUCN. At least 10 of these species are endemics, and several new species are likely to be discovered.

Potential of a Probiotic Cure

The pathogen Bd can be readily eliminated in captive frog populations with fungicides, or heat treatment, but massive treatment applications in wild situations would likely cause irreparable harm to natural ecosystems. Thus, alternative solutions are required, with the most promising abatement tool being the probiotic approach pioneered by Reid Harris and colleagues. These investigators recently identified several species of bacteria proliferating on the skin of certain amphibians that produce anti-fungal chemicals that inhibit Bd growth. Particularly exciting has been the observation that treating uninfected juvenile Rana mucosa (Mountain Yellow-Legged Frogs) with the anti-Bd bacterium Janthinobacterium lividum decreases mortality to subsequent experimental Bd exposure. Specifically, 100% of bacteria-treated frogs survived exposure to Bd compared to 60% mortality in untreated controls 16.

Panama Amphibian Rescue and Conservation Project Strategy

Recognizing that Panama’s rich diversity of amphibians is an important natural treasure with significant direct, cultural, biomedical, ecological and existence values that warrants protection from extinction, a group of organizations came together to respond to the crisis. Africam Safari Park (Mexico), Cheyenne Mountain Zoo (Colorado), Defenders of Wildlife (Washington, D.C.), Summit Municipal Park (Panama), the Smithsonian National Zoological Park (Washington, D.C.), the Smithsonian Tropical Research Institute (Panama), Zoo New England (Massachusetts) and Houston Zoo (Texas) have pooled their energy and resources, collectively pledging more than $750,000 in cash and in kind over the next three years to the Panama Amphibian Rescue and Conservation Project.

The Project will consist of three distinct and complementary parts: 1) the ongoing operation of El Valle Amphibian Conservation Center (EVACC) in Western Panama,run by the Houston Zoo; 2) the amphibian chytrid cure research program to be initiated at the National Zoo in collaboration with VanderBilt University; and 3) the construction and operation of the new Summit Park Amphibian Rescue Center in Panama. One “amphibian rescue pod” which is a biosecure, modified shipping container that will house the first rescued species from Eastern Panama has already been established.

References

  1. Stuart, S., et al., Status and Trends of Amphibian Declines and Extinctions Worldwide, in Science. 2004, American Association for the Advancement of Science. p. 1783-1786.
  2. IUCN, Redlist of Endangered Species. http://www.iucnredlist.org, 2007: p. Accessed 23 April 2008.
  3. Muths, E., et al., Evidence for disease-related amphibian decline in Colorado. Biological Conservation, 2003. 110: p. 357-365.
  4. Richards, S.J., K.R. McDonald, and R.A. Alford, Declines in populations of Australia’s endemic tropical rainforest frogs. Pacific Conservation Biology, 1993. 1: p. 66-77.
  5. Pounds, J.A., et al., Tests of Null Models for Amphibian Declines on a Tropical Mountain. Conservation Biology, 1997. 11(6): p. 1307-1322.
  6. Lips, K.R., et al., Riding the Wave: Reconciling the Roles of Disease and Climate Change in Amphibian Declines. PLoS Biol, 2008. 6(3): p. e72.
  7. Laurance, W.F., K.R. McDonald, and R. Speare, Epidemic Disease and the Catastrophic Decline of Australian Rain Forest Frogs. Conservation Biology, 1996. 10(2): p. 406-413.
  8. Berger, L., et al., Chytridiomycosis causes amphibian mortality associated with population declines in the rain forests of Australia and Central America. Proceedings of the National Academy of Sciences of the United States of America, 1998. 95(15): p. 9031.
  9. Longcore, J.E., A.P. Pessier, and D.K. Nichols, Batrachochytrium dendrobatidis gen. et sp. nov., a chytrid pathogenic to amphibians. Mycologia, 1999. 91(2): p. 219-227.
  10. Pounds, J.A., et al., Widespread amphibian extinctions from epidemic disease driven by global warming. Nature, 2006. 439: p. 161-167.
  11. Burrowes, P.A., R.L. Joglar, and D.E. Green, Potential causes of amphibian declines in Puerto Rico. Herpetologica, 2004. 60(2): p. 141-154.
  12. Dreitz, V.J., Issues in Species Recovery: An Example Based on the Wyoming Toad. BioScience, 2006. 56(9): p. 765-771.
  13. Lips, K.R., et al., Emerging infectious disease and the loss of biodiversity in a Neotropical amphibian community. Proceedings of the National Academy of Sciences of the United States of America, 2006. 103(9): p. 3165-3170.
  14. Grow, S., Amphibian Conservation Resource Manual. 2007, American Association of Zoos and Aquaria. p. 208.
  15. Woodhams, D.C., et al., Chytridiomycosis and Amphibian Population Declines Continue to Spread Eastward in Panama Ecohealth, 2008. DOI 10.1007/s10393-008-0190-0(Onlinefirst).
  16. Harris, R.N., et al., Skin microbes on frogs prevent morbidity and mortality caused by a lethal skin fungus. International Society for Microbial Ecology Journal, 2009. 1751-7362/09: p. 1-7.
  17. Wake, D.B. and V.T. Vredenburg, Are we in the midst of the sixth mass extinction? A view from the world of amphibians. Proceedings of the National Academy of Sciences, 2008. 105(Supplement 1): p. 11466.
  18. Lips, K.R., et al., Emerging infectious disease and the loss of biodiversity in a Neotropical amphibian community. Proceedings of the National Academy of Sciences, 2006. 03(9): p. 3165-3170.
  19. Woodhams, D.C., et al., Chytridiomycosis and Amphibian Population Declines Continue to Spread Eastward in Panama. EcoHealth, 2008. DOI: 10.1007/s10393-008-0190-0(5): p. 268-274.
  20. Rovito, S.M., et al., Dramatic declines in neotropical salamander populations are an important part of the global amphibian crisis. Proceedings of the National Academy of Sciences, 2009.
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