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Biodiversity Has Impact

Frog

Small predator diversity reduces parasites in frogs.

Biodiversity, including small preadators such as dragonflies and other aquatic bugs, may improve the health of amphibians, which have marked declines, by attacking and consuming the parasites that affect them, according to researchers in the college. The study suggests that dwindling global environmental biodiversity and worldwide spikes in infectious diseases may be linked.

In the study, which included a series of laboratory experiments, field surveys, and mathematical modeling, the presence of various species of dragonfly larvae reduced infections in frogs caused by parasitic flatworms called trematodes, said Val Beasley, professor and head of the Department of Veterinary and Biomedical Sciences.

Beasley said that various species of trematodes penetrate tadpoles, sometimes killing them and at other times weakening them with tissue damage, kidney failure, or severe limb deformities when the tadpoles develop into frogs. He added that other vertebrate species commonly catch trematode infections from bodies of water. These include wildlife, domestic animals, and humans (mostly children) who are commonly affected by schistosomiasis in tropical parts of the world.

The researchers, who released their findings in February in the Proceedings of the National Academy of Sciences, did not see a similar reduction in trematode infections in the presence of larval damselflies, which are intraguild predators, meaning they attack and kill not only the parasites but also the tadpole hosts.

—Matt Swayne