A horrific fungus that has threatened to wipe out many amphibians has seemed like an unstoppable foe, but new research shows that at least some frogs appear to be making a comeback.
The fungus, known most widely simply as the chytrid fungus, is something out of a horror story.
Chytrid fungus latches onto a frog’s delicate skin while the frog is swimming. It then puts down roots and starts to grow, causing a catastrophic barrier to the frog’s ability to absorb water and air.
Chytridiomycosis, as the associated disease is known, literally begins to suffocate and dehydrate its host, while also interrupting a frog’s ability to regulate its own temperature. This leads to outward signs of infection like reddened skin, convulsions, accumulations of dead skin, ulcers and bleeding.
It will also cause the frogs to display a range of unusual behaviors including a failure to seek shelter from adverse weather or predators, and postural and reflex changes. Eventually, the infected frogs die of cardiac arrest.
There are currently no known ways of curing this disease, and with an infection that has spread to literally hundreds of amphibious species so far, it has been dubbed the “worst infectious disease” ever recorded in the vertebrate population.
But now there is a small sign that, thanks to evolutionary adaptation, some frogs could bounce back.
FROGS FIGHTING BACK AGAINST THE DEADLY CHYTRID FUNGUS
Researchers from the University of Nevada have been tracking frog populations since 2004.
What the researchers have found is that several of the species they have been tracking showed massive population drops as chytrid fungus took its toll. Indeed, there are eye witness accounts of forest floors in places like Panama littered with dead and dying frogs, so deadly is the water-borne disease.
But, among those figures a new pattern has started to emerge in recent years: some populations are recovering, and even finding levels that are around where they were prior to chytrid taking hold.
“It offers us all hope,” Jamie Voyles at the University of Nevada in Reno told New Scientist.
The change isn’t in the fungus but in the frogs. Nine to 12 of the frog species the researchers have studied seem to be bouncing back, indicating that they’re becoming resistant to chytrid fungus.
It’s important to stress that the number of frog species that are showing recovery is only a fraction of the number who have been hit by this disease — around nine out of 70 or more possibly-infected species. However, given how dire the situation appeared before, even this small reprieve is something to celebrate.
So what exactly is going on here? The study reporting this finding, which appears online in the journal “Science“, has found no evidence that the fungus itself has changed. Rather, it suggests that the frogs have somehow got ahead of the fungus, which is unusual given how relatively short a fungus’ life cycle is and how quick they can manifest adaptations.
A lot is still unknown about how chytrid passes between frogs, though. Scientists will be keen to discover what trait might be giving some species a boost and whether it is something they can exploit to help other frog species who haven’t been so quick to recover, but that’s a long way off and this research didn’t offer any clues.
Still, the fact that any frog species are showing some resistance is encouraging and suggests that nature may yet be able to provide a solution. It’s worth pointing out, however, that even those species that have recovered still face massive pressures.
A loss of habitat from deforestation and water contamination threatens amphibious species. In addition, there is some evidence to suggest that climate change may be making diseases like chytridiomycosis more widespread, a trend that will only continue if we don’t halt global warming.
Clearly, the world’s frogs are not out of the woods yet, but this small study is a sign that there may yet be some hope for amphibian recovery–that is, if we also do everything we can to support them.
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