Virus kills 200,000 tadpoles overnight on Brunswick pond
BRUNSWICK (WGME) -- Hundreds of thousands of tadpoles, dead overnight. And that was just on one pond. A biology professor at Bowdoin College discovered the mass die-off of wood frog tadpoles right in his own back yard. But what killed them? And what does this mean for their future?
Bowdoin College Biology Professor Nat Wheelwright is fond of frogs. And the wood frog is one of his favorites. But last summer, he saw something he had never seen before. Something disturbing. It was a mass die off of wood frog tadpoles on his pond.
Wheelwright says last June, there were 200-thousand tadpoles swimming around his pond. 24 hours later, none of them were living. He says "I've never seen 200,000 of anything die so fast." He said to himself "What the heck happened here? I've got to figure it out."
Tests confirm an emergent disease known as a ranavirus killed the tadpoles. The virus enters directly into the cells of the tadpole causing swelling, hemorrhaging and death. Wheelwright says "The tadpoles get pinkish under their throat and at the base of their developing legs."
He says "Their skin starts to shred off and they die." What's interesting, though, is the disease is only fatal to spotted salamander and wood frog tadpoles. Wheelwright says ranaviruses are likely carried by other creatures on his pond like this green frog, bullfrogs and turtles.
He says "This virus is an interesting virus because it doesn't kill everything. And green frog is an example of a species that will carry the virus, but it doesn't affect them." Ranaviruses don't affect humans either. Wheelwright says "There's no threat at all of this virus for humans."
Wood frogs are still one of the most abundant frogs in Maine, and are not at all endangered. But these ranaviruses do pose a threat to the wood frog. Wheelwright says this is a good chance to study the impact of ranaviruses on wood frogs, while they are still common in Maine.