Amphibian Pandemic

One of the unfortunate hallmarks of the human condition is our purposeful or incidental reduction of biodiversity everywhere we go. Most obvious was the elimination of large herbivores from woolly mammoths to giant ground sloths. This makes a certain sense as they were prey species which fed our rapid expansion across the planet.

Global warming, by forcing changes to the climate, impacts all life on the planet. Fauna are indirectly threatened by simple reduction of suitable habitat. The International Union for the Conservation of Nature (IUCN) has identified habitat loss as a main threat to 85% of all species described in the IUCN’s “Red List” (those species officially classified as “Threatened” and “Endangered”).

A common example is when forested areas are cleared and converted to agricultural use. The destruction of diverse forests in southeast Asia for use as palm oil plantations threatens everything from Orangutans to Tigers.

An incidental apocalypse is now occurring with amphibians worldwide. The class Amphibia has existed for over 300 million years. Today frogs, toads, salamanders, and the lesser known caecilians are dispersed worldwide and exist in a number in niches from rain forests to deserts. A northern most amphibian is the wood frog of Alaska which literally freezes up during the winter. When the weather warms it thaws and goes about its business.

Compounding threats to amphibians from habitat loss and climate change is a rapidly expanding pandemic of a Chytrid fungus, specifically Batrachorchytrium dendrobatidis (BD.) The fungus has been know for over a century in parts of east Asia and Africa but only in the past few decades has it spread worldwide.

There are several hypotheses for the mechanism of dispersion. In the 1930s a British researcher by the name of Lancelot Hogben, hence the eponymous Hogben test, found that injecting urine from a pregnant woman into the the African Clawed Frog induce the frog to lay eggs. The test was faster and didn’t require the sacrifice of the animal as was the case in the rabbit test. It was used on several continents from the 1940s to 1960s.

Recent study of the DNA of numerous samples suggests the origin of the BD dispersion began on the Korean peninsula in the early 1950’s. The Korean war, with the massive movement of men and materiel in and out of the area could have dispersed the fungus. The fungus can easily be transported on any kind of moist material, in addition to the amphibians themselves.

The global trade in amphibians for foods and pets is probably responsible for the dispersion of new strains which may be even more toxic. BD grows on the skin of amphibians. Amphibian skin is responsible for much metabolic activity such gas exchange. Essential electrolytes, Sodium and Potassium are also exchanged across the skin and it is a disruption of electrolyte balance that kills them.

Of the roughly 7000 amphibian species, 200 have recently been extirpated, and another 2000 are threatened. Nearly half of all amphibian species are in decline. Defenders of Wildlife here in the United States has called for the Fish and Wildlife service to ban the import of amphibians.

The moral of this story is that we ought to leave the critters be. Transporting them from hither to you could very well accelerate the amphibian pandemic.

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