WASHINGTON (Reuters) - A rare and primitive frog living in a remote Borneo stream has no lungs and apparently absorbs oxygen through its skin, researchers reported on Wednesday.
The aquatic frog has evolved backwards, re-acquiring a primordial trait, David Bickford of the National University of Singapore and colleagues reported.
Studying the frog could help shed light on how lungs evolved in the first place, they wrote in the journal Current Biology, adding that illegal gold mining in the area may threaten the unique species.
"The evolution of lunglessness in tetrapods (amphibians, reptiles, birds, and mammals) is exceedingly rare, previously known only from amphibians -- two families of salamanders and a single species of caecilian (blindworm)," they wrote.
"Here we report the first case of complete lunglessness in a frog, Barbourula kalimantanensis, from the Indonesian portion of Borneo."
The frog may be endangered because of mining activity, the researchers said.
"In August 2007, we visited ... near NangaPinoh, Western Kalimantan but found that illegal gold mining had destroyed all suitable habitats in the vicinity," they wrote. They snorkeled, waded and turned over boulders to find their quarry.
"The originally cool, clear, fast-flowing rivers are now warm and turbid. Water quality around the ... locality is no longer suitable for the species, but we were able to re-discover two new populations upstream," they added.
"We knew that we would have to be very lucky just to find the frog," Bickford said in a statement.
Animals evolved lungs when they moved from the sea to land millions of years ago. Animals have only lost this important adaptation a few times, Bickford's team said.
"The discovery of lunglessness in a secretive Bornean frog, supports the idea that lungs are a malleable trait in the Amphibia, the sister group of all living tetrapods. Amphibians maybe more prone to lunglessness since they readily utilize other methods for gas exchange," they wrote.
"This is an endangered frog that we know practically nothing about, with an amazing ability to breathe entirely through its skin, whose future is being destroyed by illegal gold mining by people who are marginalized and have no other means of supporting themselves," Bickford said.
Only animals with small body sizes, slow metabolisms and living in fast-flowing cold water where oxygen and carbon dioxide are exchanged quickly may be able to survive without lungs, the researchers said.
"We strongly encourage conservation of remaining habitats of this species," they recommended.
(Reporting by Maggie Fox; Editing by Cynthia Osterman)
The aquatic frog has evolved backwards, re-acquiring a primordial trait, David Bickford of the National University of Singapore and colleagues reported.
Studying the frog could help shed light on how lungs evolved in the first place, they wrote in the journal Current Biology, adding that illegal gold mining in the area may threaten the unique species.
"The evolution of lunglessness in tetrapods (amphibians, reptiles, birds, and mammals) is exceedingly rare, previously known only from amphibians -- two families of salamanders and a single species of caecilian (blindworm)," they wrote.
"Here we report the first case of complete lunglessness in a frog, Barbourula kalimantanensis, from the Indonesian portion of Borneo."
The frog may be endangered because of mining activity, the researchers said.
"In August 2007, we visited ... near NangaPinoh, Western Kalimantan but found that illegal gold mining had destroyed all suitable habitats in the vicinity," they wrote. They snorkeled, waded and turned over boulders to find their quarry.
"The originally cool, clear, fast-flowing rivers are now warm and turbid. Water quality around the ... locality is no longer suitable for the species, but we were able to re-discover two new populations upstream," they added.
"We knew that we would have to be very lucky just to find the frog," Bickford said in a statement.
Animals evolved lungs when they moved from the sea to land millions of years ago. Animals have only lost this important adaptation a few times, Bickford's team said.
"The discovery of lunglessness in a secretive Bornean frog, supports the idea that lungs are a malleable trait in the Amphibia, the sister group of all living tetrapods. Amphibians maybe more prone to lunglessness since they readily utilize other methods for gas exchange," they wrote.
"This is an endangered frog that we know practically nothing about, with an amazing ability to breathe entirely through its skin, whose future is being destroyed by illegal gold mining by people who are marginalized and have no other means of supporting themselves," Bickford said.
Only animals with small body sizes, slow metabolisms and living in fast-flowing cold water where oxygen and carbon dioxide are exchanged quickly may be able to survive without lungs, the researchers said.
"We strongly encourage conservation of remaining habitats of this species," they recommended.
(Reporting by Maggie Fox; Editing by Cynthia Osterman)
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original paper:
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The Bornean Flat-headed Frog (Barbourula kalimantanensis) is a species of toad in the Bombinatoridae family. It is notable as the only frog known to have no lungs, although lungless species have also evolved in the two other amphibian orders caecilians (Atretochoana eiselti) and salamanders (family Plethodontidae and genus Onychodactylus).
The frog, no more than 40 mm long, lives in cold, fast rivers in remote areas of the rainforests of Kalimantan, the Indonesian part of the island of Borneo.[1][2]
Its natural habitats are subtropical or tropical moist lowland forests and rivers. It is threatened by habitat loss from toxic metals used in mining and other unfortunate consequences of development on the island.[1]
Djoko Iskandar first came across the frog 30 years ago and has been searching for it ever since. He didn't know the frog was lungless until they cut eight of the specimens open in the lab. It has the rare characteristic of being an amphibian without lungs, and instead breathes entirely through its skin.[1] Instead, other internal organs (the stomach, spleen and the liver) take up the space which normally would be filled by the lungs.[1] By retaining the lunglessness of their tadpole stage, the frogs can flatten their bodies, which they have a tendency to do in water to help absorb oxygen and avoid being swept away.[3][1] The Axolotl in Mexico is a similar case, except that it retains its gills.
It was first described by Djoko Iskandar, an Indonesian zoologist, in 1978.[4]
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References
1. Choi, Charles Q.. "Scientists find bizarre lungless frog", MSNBC, 2008-04-07. Retrieved on 2008-04-08.
2. Casey, Michael. "Frog with no lungs found in Indonesian wild", The Globe and Mail, Toronto, April 10, 2008 at 1:09 PM EDT. Retrieved on 2008-04-10.
3. http://news.yahoo.com/s/ap/20080410/ap_on_fe_st/indonesia_lungless_frog Yahoo's Coverage of this exotic frog.
5. Iskandar, Djoko T. (December 28, 1978). "A New Species of Barbourula: First Record of a Discoglossid Anuran in Borneo". Copeia 1978 (No. 4): 564-566. American Society of Ichthyologists and Herpetologists.
6. Bickford, David et al., Current Biology (6 May 2008)
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