Runoff blamed for deformed of leopard frogs in Minnesota

The above photo shows a leopard frog with two extra deformed hind legs.

The mystery of deformed frogs in a pond ( more than half of the leopard frogs had missing or extra limbs) at Minnesota which has puzzled researchers for more than a decade has finally been solved.

According to researchers led by Pieter Johnsonof the University of Colorado, Boulder, the growing number of deformedfrogs in recent years is caused by infection by a type of parasite worm - called trematodes, due to the increasing amount of runoff from farming and ranching.

The parasites have a series of host species. They grow in snails and become infectious when released by the snails into ponds, where they can infect frog tadpoles, forming cysts in the developing limbs. Water birds eat the frogs and then excrete the parasites back into the ecosystem where they can infect the snails. The increasing amount of runoff is fueling a boom in algae growth, the snails eat the algae and also undergo a population explosion, increasing the breeding places for the trematodes. [Quoted from China Daily]