19:00 22 October 2009 by Bob Holmes
The fungus now decimating frog populations around the world does its damage by impairing the animals' ability to absorb electrolytes through their skin. This discovery may eventually lead to treatments that make the disease less lethal.
Biologists now generally agree that the fungal disease known as chytridiomycosis is responsible for the worldwide die-off of frogs that has caused a conservation crisis in recent years. However, the fungus affects only the outer layers of the skin, leaving few clues to why it is so lethal.
But now Jamie Voyles of James Cook University in Townsville, Australia, and colleagues have an answer. In diseased frogs, the skin's ability to take up sodium and potassium ions from the water decreases by more than 50 per cent, they found. As a result, the concentration of these two ions in the frogs' blood fell by 20 and 50 per cent, respectively. This ion loss – similar to the hyponatraemia that a human athlete might experience from drinking too much water too fast – eventually leads to cardiac arrest and death.
The researchers found they could delay death by giving diseased frogs an oral electrolyte-replacement solution – a sort of froggy Gatorade. Fungal damage to the skin was too extensive for this to prevent death altogether, the study represents a first step toward finding an effective treatment for the disease, Voyles says.
Journal reference: Science, DOI: 10.1126/science.1176765
(Submitted by Tim Chapman)