There's a parasite called a frog-mutating flatworm (Ribeiroia ondatrae) which induces frogs to grow extra hind legs. But this particular ... to infect or grow on living animals.

Frogs have long hind legs for leaping and swimming ... Frogs like to divide their activities between both land and water, living in and around ponds, lakes and streams where they can absorb ...

leopard frogs were widely collected not only for dissection but for the food industry (frog legs) as well. However, massive declines beginning in the early 1970s, particularly in Canada and the ...