Discovering Amphibians: Frogs and Salamanders of the Northeast by John Himmelman

Author:John Himmelman
Language: eng
Format: epub
ISBN: 9781461745075
Publisher: Down East Books

He goes on to say that “Stress-related disease is the one consistent factor that may link amphibian deaths worldwide, and we have demonstrated that amphibian stress in the Cascades is ultimately linked to recent global climate fluctuations.”

Based on this and other studies, it seems that while ozone depletion and consequent higher UV radiation exposure can play a role in weakening its victims, the knockout punch comes from elsewhere. In the last couple decades we’ve lost three percent of our ozone. What happens if it gets to six percent or ten percent? Right now, increased UV levels could be mutating, and killing, amphibians all over the planet at an alarming rate. They’re also being blamed for increased rates of skin cancer and glaucoma in humans. If we can figure out what’s causing these amphibian malformations and this global die-off, we humans will most likely benefit. If there are so many contaminants in the water that it’s brewing up twelve-legged frogs, then maybe that’s telling us something about the water we humans also rely on to stay alive. If the sun is baking frog embryos into three-eyed curiosities, that may be telling us that we need to do something to keep that protective ozone blanket above us.

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A third culprit is also being blamed for frog malformations—parasites. About ten years before the discovery of malformed frogs on that middle school outing, herpetologist Stephen Ruth came upon a site in California where hundreds of long-toed salamanders and Pacific treefrogs were exhibiting a wide array of abnormalities. He contacted colleague Stanley K. Sessions, who first suspected chemicals in the water. However, water samples tested clean. What they discovered instead were cysts in the malformed amphibians. The cysts were from parasitic trematodes, which are also known as flatworms or flukes. About forty known species of trematodes are considered to be parasites. The ones found by Sessions are in the genus Ribeiroia, and while unnamed at the time of their discovery, are now called Ribeiroia ondatrae.

Ribeiroia trematodes enter a water body in their adult stage via droppings from birds, most typically herons, raptors, and ducks. They lay eggs in their new habitat, and the eggs hatch into miracidia, a larval stage that enters mollusks, such as pond snails, to continue their development. They change form again, into cercariae, grow a little squiggly tail, and find their next host, a frog or salamander larva. There, they burrow into the skin, sometimes right where the leg buds are forming, and form metacercarial cysts. Birds then eat the amphibians, and the cycle continues.

Closer study of the California frogs and salamanders revealed high concentrations of tiny round cysts at the base of leg joints. Sessions believed that their presence caused the leg buds to grow abnormally. He tested his hypothesis by placing glass beads, the size of trematode cysts, in the leg buds of developing frogs and salamanders. This resulted in frogs with malformed or extra limbs. The manner of the deformities mirrored what was being observed in the wild. Sessions

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