Stories tagged ecosystems

Dec
14
2008

Note: original title using the term fertilizer was corrected to read atrazine
Leopard frog
Leopard frogCourtesy Heather Dietz

What is happening to our frogs?

A recent study showed that atrazine in pond water could lead to a higher population of snails, which harbor parasites that also infect frogs. For the study, Lucinda Johnson and her colleagues at UMD collected leopard frogs from 18 wetlands near St. Cloud, Minnesota. The researchers found a positive correlation between the amount of atrazine in a wetland and the number of parasites in that wetland's frogs. The parasite in question is a tiny worm called a trematode. They can have a negative effect on frog populations.

How atrazine effects frogs

More fertilizer = more pond scum (periphyton)
More periphyton (snail food) = more snails
More snails = more snail parasites (trematodes)
More trematodes = more trematode larva attacking tadpoles
Larva infested tadpoles and frogs have lower survival rates when atrazine is present

The trematode worm that infects the frogs gets passed to frog-eating birds like herons and egrets. Inside the birds, the worms develop to adulthood. The adults produce eggs that are released into water with the birds' feces. The eggs hatch, develop into larvae, and burrow into snails. After further development, they burrow their way out again and swim in search of tadpoles. They infect them, the tadpoles turn into frogs, and the cycle continues.

Learn more about atrazine and frogs

Source articleUMNews: The tadpoles tale .
Article in Nature: Agrochemicals increase trematode infections in a declining amphibian species