May 25th, 2013 by Michael Ricciardi
Two important amphibian news items to report here…the first regards the spread of the lethal Chytrid fungus into Caecilians (a third major grouping of the Amphibia); the second item: a report on the recent USGS survey of US amphibian populations.
Rare Amphibian Group Now at Risk from Frog-killing Fungus
Frogs (and toads), salamanders, and Caecilians — a lesser known amphibian looking somewhere between a large worm or a smallish snake — represent the three major groups of amphibians.
For the past two decades at least, a lethal fungus (Batrachochytrium dendrobatista) — generally known as Chytrid fungus or Bd — has spread through frog and salamander populations around the world, decimating local populations, causing extinctions (almost 300 world wide), and threatening to wipe out an estimated one third of the world’s frog and salamander species in the coming years.
The caecilian (pronounced like “Sicilian”) amphibian group is fairly rare and rarely studied. There are about 190 known caecilian species with the largest reaching a length of almost 2 meters. It was once believed that the legless caecilians were not at risk for the chytrid infection — possibly due to their secretive life cycles in deep soils.
No more. In a global survey of caecilians conducted by the Natural History Museum and the Zoological Society of London, England, scientists captured more than 200 caecilian specimens comprising 29 species. Examination of the skin of the live specimens revealed 58 individuals infected with the Bd fungus many of which subsequently died from the infections.
The fungal disease — called chytridiomycosis — primarily infects the skin of amphibians, blocking the absorption of oxygen (which is how most Amphibia get their oxygen) and water and probably interfering with other critical, cellular functions. There is no known cure for the disease and the origins of the fungus are likewise unknown (but may be more than 40,000 years old). Its spread is believed to have been enabled by the global, commercial frog trade (note: frogs are sold for pets, food, dissection kits, and even for pregnancy tests) which emerged in the latter half of the 20th Century. The fungus can also travel on the legs of migrating birds and can survive in water for lengthy periods.
In a press release, museum zoologist and lead researcher David Gower stated:
“The fungus was known to infect and potentially kill both the other major groups of amphibians, but we did not know if it definitively could infect caecilians in the wild, and whether it could potentially also kill them. We now know both of these are the case, and so this potentially major threat needs to be taken into consideration in caecilian conservation biology.”
The results of the survey are detailed in the May 2013 issue of EcoHealth.
Source material for this post cam from the SciAm article: ‘Frog-Killing Chytrid Fungus Hits Rarely Seen, Wormlike Amphibians’ by John R. Platt
US Geological Survey of US Amphibians Finds Troubling Trend
US frog, toad and salamander populations are declining at a rate of 3.7 percent per year, according to the recent completed USGS Amphibian Research and Monitoring Initiative. At that rate, nearly one half of these amphibians will have disappeared from their native habitats 20 years out.
The “alarming” news holds true even for species thought to be “safe” — with a decline rate of 2.7 percent per year.
Amphibians have been facing a “quadruple threat” for many years now — a combination of chytrid infections, climate change, pollution and habitat destruction. This survey represents the first time that US amphibian declines have actually been measured.
“These are really ancient species that have been surviving a long time on earth through all kinds of changes. It’s just a concern to see,” said USGS ecologist Michael J. Adams, “They just disappear. Populations are going away.”
Worldwide, the news is worse. According to the “red list” compiled by the International Union for Conservation of Nature, the rate of decline amongst amphibian species, globally, is an astounding 11.6 per year, which means that in 6 years or so, half of known amphibian sites will be “unoccupied”. Currently, one third of all members of the Amphibia class are on the IUCN red list.
The survey initiative transpired over a nine year period and included 34 study areas (comprised of hundreds of ponds, streams, and other sites). Scientists returned to each site every two or three years to conduct inventories of amphibian species. Most of the sites were on public lands and under some form of state or federal protection — making the observed declines even more of a concern.
The USGS survey did not investigate the causes of the declines (which can involve many interacting factors operating over wide regions), only their trends during the study period. But efforts are underway to conserve many species and remove or mitigate some of the more local causes (while climate change impacts will be nearly impossible to stop).
Amphibians provide an important ecosystem service by feeding on many types of insects and helping to maintain rich soils; they are important links in their respective ecosystems; their declines — the loss of biodiversity — bode poorly for ecosystem stability in the long term.
USGS Amphibian Research and Monitoring Initiative was published Wednesday in the online journal PLOS One.
Some source material (and quote) for this post came from the AP/Yahoo news article: ‘Study: Amphibians disappearing at alarming rate‘ by Jeff Barnard
To learn more about what you can do to help survey and save amphibians wherever you live — check out this important Planetsave post and consider becoming a ‘citizen scientist’ and joining the Amphibian Blitz Project!
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