Groovy23
Environmentalist
Reged: 09/08/06
Posts: 1083
Loc: Central London, UK.
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Sunbathing tree frogs may hold the key to understanding how a deadly fungus is wiping out amphibians around the world. The Chytrid Fungus has been implicated in many amphibian extinctions.
Click here to watch video
Now scientists are using non-invasive imaging technology to find out how some frogs from Central America may be able to beat this deadly disease.
They believe that the frogs' unusual skin is allowing the animals to bask in hot sunlight, possibly boosting their temperatures to kill off the fungus.
Most frogs avoid prolonged exposure to sunlight; the light and heat dry out their skin. However, some tree frogs from Costa Rica thrive in these conditions.
The team wanted to study the frogs' skin without harming the animals
Andrew Gray, curator of herpetology at Manchester Museum who keeps a large collection of frogs from this area, said: "They sit in the Sun and bask for long periods without doing themselves any harm.
"However, until now, nobody has really looked at how they do this."
The challenge, he said, was to find ways of examining the frogs' skin in detail without harming the creatures, some of which are extremely endangered.
So the researcher teamed up with physicists from the Photon Science Institute at the University of Manchester.
Dr Mark Dickinson said: "I had been working on a new imaging technology called Optical Coherence Tomography ( OCH ) for medical imaging.
Optical coherence tomography tomogram of a fingertip.
"But when Andrew approached me, I thought that this would be perfect for the frogs - it can show us what is happening in the frogs' skin but it is non-invasive."
Hot stuff
The OCT revealed that the frogs had an unusual pigment in their skin, called pterorhodin, that was allowing the creatures to reflect light in the infrared spectrum rather than absorb it. Melanin, the pigment typically found in skin, absorbs light.
Some believe the frogs could be reflecting light so they can blend in with the leaves they sit on, which also reflect at these wavelengths, to hide from predators that can only see in the infrared range.
But Mr Gray said: "We believe that the frogs are also reflecting the light and heat for thermoregulation - to cool themselves down. The surface of the skin is hot, while the body stays cool."
Some of these sunbathing frogs even take on a slightly metallic sheen as they bask in the sun, he added.
"Is this their natural defence against the fungus?"
Andrew Gray
He believes that the unusual reflective skin structure revealed by OCT could help scientists to better understand how the chytrid fungus (Batrachochytrium dendrobatidis) is affecting frogs.
Mr Gray said: "The chytrid fungus lives in the skin of the frog, but it can only live at certain temperatures.
"It has been shown with frogs in captivity that if you elevate the skin temperature for short periods, you can clear them of the fungus.
"We thought: 'what if the sunbathing frogs are doing this naturally?'; is this their natural defence against the fungus?"
If temperature regulation is linked to the chytrid fungus, recent climate changes in the regions where the frogs live could have affected their ability to fight off infections - causing the recent dramatic declines, said Mr Gray.
"In Costa Rica, in the Monteverde Forest, conditions have changed a lot in the past 10 years.
"There is now much more cloud cover, which leaves the frogs with less opportunities for sunbathing, and for possibly clearing themselves of the fungus."
The team is now using the OCT technique to see how different species of frogs that carry the special pigment reflect light, and also to study the skin structure in frogs that do not carry the pterorhodin pigment.
They believe that the amphibians' differences in ability to reflect may explain why some species are coping better with chytrid infections than others.
Source: BBC
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Edited by Groovy23 (06/24/08 01:21 PM)
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Hill
Master Guide
Reged: 10/31/04
Posts: 8870
Loc: Los Angeles
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Interesting stuff Groovy. Now all we have to do is to get all of the shade loving frogs to develop an affinity for getting a good tan.
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Groovy23
Environmentalist
Reged: 09/08/06
Posts: 1083
Loc: Central London, UK.
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Scientists are set to begin a hunt for the some of the world's rarest frogs in Costa Rica, including the iconic golden toad, last seen some 20 years ago.
A team from Manchester University and Chester Zoo are in Costa Rica to track down the highly endangered creatures.
Click here to watch video
The golden toad has vanished from Costa Rica's rainforests
BBC News will follow their trek deep into the cloud forests of Monteverde.
Amphibians numbers around the world have crashed, in part because of a deadly fungus. Costa Rica has been particularly badly hit.
Expedition leader Andrew Gray, from the University of Manchester's Manchester Museum, said: "Costa Rica's highlands used to be major biodiversity hotspots - but in many areas amphibian populations have been completely decimated."
Killer fungus
In the late 1980s, herpetologists around the world found that amphibian populations were suffering unprecedented declines, but they struggled to understand exactly why.
The harlequin toad has been badly hit by the chytrid fungus
A decade later, researchers isolated a previously unknown fungus, Batrachochytrium dendrobatidis, which was infecting amphibians, effectively suffocating them by making it impossible for them to breathe across their skin.
Recently, the scientists working on the Global Amphibian Assessment estimated that one-third of all amphibians were threatened by extinction and about 120 species had already become extinct since the 1980s.
Many believe the disease caused by the chytrid fungus is a key factor for this crash. Other causes are thought to include habitat destruction and changes in climate.
Frog rediscovery
Countries in Central America have been particularly badly affected by the deadly chytrid fungus, which is now widespread there. A great deal of effort is now being put into place to safeguard any remaining species.
Andrew Gray said: "For the last 10 years, I've been working with others to ensure the future for frogs that have so far escaped extinction.
"One of the main things I have been doing is establishing breeding populations in Manchester Museum for a number of very, very rare species - including the splendid leaf frog (Cruziohyla calcarifer), the yellow-eyed leaf frog (Agalychnas annae) and the lemur leaf frog (Hylomantis lemur).
"I've also been working with the Costa Rican authorities and scientists to put conservation measures into place at the sites where any rare frogs are found."
Last year, Mr Gray caught a glimpse of the Ithsmohyla rivularis in the cloud forests of Monteverde - a frog that was thought to have gone extinct about 20 years ago.
He said: "To find this species last year that was thought to have become extinct at the same time as the golden toad was incredible - it is the rarest tree frog in the world."
To find this species last year that was thought to be extinct at the same times as the golden toad was incredible.
Andrew Gray
He has now been given special permission by the Costa Rican authorities to collect some of the frogs to take back to Manchester.
He told the BBC: "We are returning to thoroughly search the site in the hope of finding more specimens.
"It's not going to be easy - they live deep in the Monteverde rainforest, they are only a couple of centimetres in size and they only come out in the dead of night - and while the males do call, the females don't make a sound."
'Never say never'
The rediscovery of Ithsmohyla rivularis has spurred the team on to also try to seek out a golden toad (Bufo pereglines).
This colourful amphibian, which scientists only discovered in 1966, became the iconic symbol of amphibian decline. In 1987 there were approximately 1,500 of the toads, but just two years later it had vanished from the face of the rainforest.
Manchester Museum has a splendid leaf captive breeding population
Mr Gray said: "We are going to be trekking through an area where the golden toad used to thrive. It is very unlikely we will find one - but as last year's discovery showed us, never say never."
Source: BBC
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