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Strange animal finds: Lungless frogs, crawling fish

April 7, 2008
Courtesy Cell Press,
University of Washington and
and World Science staff

Bi­ol­o­gists are still get­ting over their sur­prise from re­ports of two un­re­lat­ed disco­veries of strange spe­cies in the past week: a lung­less frog and a bi­zarre, crawl­ing fish.

The frog find­ing rep­re­sents first case of com­plete lung­lessness in a frog, ac­cord­ing to a re­port in the April 8 is­sue of the re­search jour­nal Cur­rent Bi­ol­o­gy. The aquat­ic frog Bar­bou­rula kali­man­ta­nen­sis ap­par­ently gets all the ox­y­gen it needs through its skin, re­search­ers said.

The leg­like pectoral fin for walk­ing re­veals this new­found fish is an ang­ler­fish, an expert says, though it lacks the cha­ract­er­is­tic ang­ler­fish's lure on its head for at­tract­ing prey. (Cre­d­it: M. Sny­der, starknakedfish.com/divingmaluku.com)


Two popula­t­ions of the aquat­ic, brown frog were found dur­ing an ex­pe­di­tion to In­do­ne­sian Bor­neo, sci­ent­ists re­ported. 

“I have to say that I was very skep­ti­cal at first [that they would lack lungs],” said Da­vid Bick­ford of the Na­tional Uni­ver­s­ity of Sin­ga­pore, a mem­ber of the re­search team. “We were all shocked when it turned out to be true for all the spec­i­mens we had from Ka­li­man­tan, In­done­sia.”

Among tetrapods, or four-limbed an­i­mals, lung­less­ness is only known in am­phib­ians. Com­plete loss of lungs in any spe­cies seems to have oc­curred only three times in ev­o­lu­tion, Bick­ford said.

The disco­very of lung­lessness in the se­cre­tive Bor­ne­an frog sup­ports the idea that lungs are a mal­le­a­ble trait in am­phib­ians, the ev­o­lu­tion­ary sis­ter group to all oth­er tetrapods, ac­cord­ing to the re­search­ers. 

B. kali­man­ta­nensis
lives in cold, fast-flowing wa­ter, they added, so loss of lungs might be an adapta­t­ion to a com­bina­t­ion of fac­tors: a high­er ox­y­gen en­vi­ron­ment, the spe­cies’ pre­sumed low met­a­bol­ic rate, se­vere flat­ten­ing of their bod­ies that in­creases the sur­face ar­ea of their skin, and neg­a­tive buoy­an­cy—mean­ing the frogs would rath­er sink than float.

The re­search­ers said that fur­ther stud­ies of this re­mark­a­ble frog may be ham­pered by the spe­cies’ rar­ity and en­dan­ger­ment. They urged con­serva­t­ion of the crea­tures’ re­main­ing habi­tats. Sadly, the frogs’ “fu­ture is be­ing de­stroyed by il­le­gal gold min­ing by peo­ple who are marginal­ized and have no oth­er means of sup­port­ing them­selves,” Bick­ford said. “There are no sim­ple an­swers.”

Sep­a­rate­ly, on April 2 a Uni­ver­s­ity of Wash­ing­ton re­searcher de­scribed a new­found fish that would rath­er crawl in­to crevices than swim, and that may be able to see in the same way that hu­mans do.

Sight­ed in In­do­ne­sian wa­ters off Am­bon Is­land, the fish has tan- and peach-colored zebra-striping, and rip­pling folds of skin that ob­scure its fins, mak­ing it look like a glass sculp­ture, said the uni­ver­s­ity’s Ted Pietsch. But far from be­ing like glass, the bod­ies of these fist-sized fish are soft and plia­ble enough to slip and slide in­to nar­row crevices of cor­al reefs. It’s probably part of why they’ve typ­ic­ally gone un­no­ticed be­fore, re­search­ers said.

The an­i­mals are an­gler­fishes, said Ted Pietsch, an au­thor­ity on an­g­ler­fish. 

Hus­band and wife Buck and Fitrie Ran­dolph, with dive guide To­by Fa­dir­sy­air, found and pho­tographed an in­di­vid­ual Jan. 28 in Am­bon har­bor. A sec­ond adult has since been seen and two more ap­par­ent ju­ve­niles were spot­ted March 26, off Am­bon. One of the adults laid a mass of eggs. Ref­er­ence books were con­sulted but noth­ing si­m­i­lar to the fish pho­tographed in Jan­u­ary was found, said Pietsch. A search for in­terna­t­ional fish ex­perts even­tu­ally led the dis­cov­er­ers to him.


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Evolutionary biologists are still getting over their astonishment from two unrelated discoveries of remarkable species in the past week: a lungless frog and a bizarre, crawling fish. The frog finding represents first case of complete lunglessness in a frog, according to a report in the April 8 issue of the research journal Current Biology. The aquatic frog Barbourula kalimantanensis apparently gets all the oxygen it needs through its skin, researchers said. Previously known from only two specimens, two new populations of the aquatic frog were found during an expedition to Indonesian Borneo. “We knew that we would have to be very lucky just to find the frog,” said David Bickford of the National University of Singapore, a member of the research team. “People have been trying for 30 years. But when we did and I was doing the initial dissections—right there in the field—I have to say that I was very skeptical at first [that they would lack lungs]. It just did not seem possible. We were all shocked when it turned out to be true for all the specimens we had from Kalimantan, Indonesia.” Among tetrapods, or four-limbed animals, lunglessness is only known in amphibians. Complete loss of lungs in any species seems to have occurred only three times in evolution, Bickford said. The discovery of lunglessness in a secretive Bornean frog supports the idea that lungs are a malleable trait in amphibians, the evolutionary sister group to all other tetrapods, according to the researchers. Barboroula kalimantanensis lives in cold, fast-flowing water, they noted, so loss of lungs might be an adaptation to a combination of factors: a higher oxygen environment, the species’s presumed low metabolic rate, severe flattening of their bodies that increases the surface area of their skin, and negative buoyancy—meaning the frogs would rather sink than float. The researchers said that further studies of this remarkable frog may be hampered by the species’ rarity and endangerment. They urged conservation of the frogs’ remaining habitats. “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. “There are no simple answers to this problem.” Separately, on April 2 a University of Washington researcher described a newfound fish that would rather crawl into crevices than swim, and that may be able to see in the same way that humans do. Sighted in Indonesian waters off Ambon Island, the fish has tan- and peach-colored zebra-striping, and rippling folds of skin that obscure its fins, making it look like a glass sculpture, said the university’s Ted Pietsch. But far from being like glass, the bodies of these fist-sized fish are soft and pliable enough to slip and slide into narrow crevices of coral reefs. It’s probably part of why they’ve typically gone unnoticed before, researchers said. The animals are anglerfishes, said Ted Pietsch, an authority on anglerfish. Husband and wife Buck and Fitrie Randolph, with dive guide Toby Fadirsyair, found and photographed an individual Jan. 28 in Ambon harbor. A second adult has since been seen and two more apparent juveniles were spotted March 26, off Ambon. One of the adults laid a mass of eggs. Reference books were consulted but nothing similar to the fish photographed in January was found. Seeking international fish experts eventually led them to Pietsch.