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Newfound frog called smallest known backboned animal

Jan. 11, 2012
Courtesy of Public Library of Science
and World Science staff

A newly dis­cov­ered frog is the world’s small­est known ver­te­brate, or back­boned an­i­mal, bi­ol­o­gists are re­port­ing.

The sci­en­tists, who iden­ti­fied the new spe­cies in New Guin­ea, de­scribe the find­ings in the Jan. 11 is­sue of the on­line re­search jour­nal P­LoS One.

The frog, which researchers said makes a cricket-like sound and is well un­der a cen­ti­me­ter long, was giv­en the sci­en­tif­ic name Pae­do­phryne ama­uen­sis. The sec­ond part of that comes from Amau Vil­lage in Pap­ua New Guin­ea, where the crea­ture was found. 

P. amanuensis sits on a U.S. dime, which is 1.8 cm (7/10 inch) long.


The adult body size for these frogs ranges from 7 to 8 mil­lime­ters, said mem­bers of the re­search team, led by Chris­to­pher Aus­tin of Lou­i­si­ana State Un­ivers­ity.

The dis­cov­ery “is of con­si­der­able in­ter­est to bi­ol­o­gists be­cause lit­tle is un­der­stood about the func­tion­al con­straints that come with ex­treme body size, wheth­er large or smal­l,” Aus­tin said. The pre­vi­ous small­est ver­te­brate was a fish, called Pae­do­cypris pro­ge­net­ica, with an adult size of 7.9 to 10.3 mil­lime­ters.

Many spe­cies of an­i­mals have evolved in­to min­ia­ture forms, Aus­tin and col­leagues not­ed.

“Miniatur­iz­a­tion, the re­duc­tion in body size ne­ces­si­tat­ing dras­tic al­tera­t­ions to an or­gan­is­m’s phys­i­ol­o­gy, ecol­o­gy, and be­hav­ior, is known from eve­ry ma­jor ver­te­brate line­age and nearly all ma­jor groups of an­i­mals,” they wrote. Frogs are pro­mi­nent con­tri­bu­tors to the le­gions of the min­iat­ur­ized, boast­ing 29 spe­cies that are un­der 1.3 cen­ti­me­ters long, they added.

Most of the min­ia­ture frogs don’t go through a tad­pole phase and are born di­rectly in frog form, Aus­tin and col­leagues wrote. Like oth­er min­i­a­tur­ized an­i­mals, they of­ten have some­what sim­pli­fied skele­tons, they added. 

The min­ia­ture frogs al­so all live in very moist habi­tats, probably be­cause of the dif­fi­cul­ty that their ti­ny bod­ies would quickly dry out oth­erwise, ac­cord­ing to the re­search­ers. Like all but two of the small­est frog spe­cies, Pae­do­phryne ama­uen­sis lives in leaf lit­ter, wet fall­en tree leaves that blan­ket the for­est floor.

The new find­ing il­lus­trates that ti­ny frogs “are not merely cu­ri­os­i­ties, but rep­re­sent a pre­vi­ously un­rec­og­nized ec­o­log­i­cal guild,” or a group of spe­cies that all de­pend on si­m­i­lar re­sources, they wrote. “Such dis­cov­er­ies are in­creas­ingly crit­i­cal in this time of glob­al am­phib­i­an de­clines and ex­tinc­tions,” they added.


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A newly discovered frog is the world’s smallest vertebrate, or backboned animal, biologists are reporting. The scientists, who identified the new species in New Guinea, describe the findings in the Jan. 11 issue of the online research journal PLoS One. The frog, which makes a cricket-like sound and is well un der a centimeter long, was given the scientific name Paedophryne amauensis. The second part of that comes from Amau Village in Papua New Guinea, where the creature was found. The adult body size for these frogs ranges from 7 to 8 millimeters, said members of the research team, led by Christopher Austin of Louisiana State University. The discovery “is of considerable interest to biologists because little is understood about the functional constraints that come with extreme body size, whether large or small,” Austin said. The previous smallest vertebrate was a fish, called Paedocypris progenetica, with an adult size of 7.9 to 10.3 millimeters. Many species of animals have evolved into miniature forms, Austin and colleagues noted. “Miniaturization, the reduction in body size necessitating drastic alterations to an organism’s physiology, ecology, and behavior, is known from every major vertebrate lineage and nearly all major groups of animals,” they wrote. Frogs are no exception, with 29 species that are under 1.3 centimeters long, they added. Most of the miniature frogs don’t go through a tadpole phase and are born directly in frog form, Austin and colleagues wrote. Like other miniaturized animals, they often have somewhat simplified skeletons, they added. The miniature frogs also all live in very moist habitats, probably because of the difficulty that their tiny bodies would quickly dry out otherwise, according to the researchers. Like all but two of the smallest frog species, Paedophryne amauensis lives in leaf litter, wet fallen tree leaves that blanket the forest floor. The new finding illustrates that tiny frogs “are not merely curiosities, but represent a previously un recognized ecological guild,” or a group of species that all depend on similar resources, they wrote. “Such discoveries are increasingly critical in this time of global amphibian declines and extinctions,” they added.