Navigation Links
When threatened, a few African frogs can morph toes into claws
Date:6/23/2008

CAMBRIDGE, Mass., June 23, 2008 Biologists at Harvard University have determined that some African frogs carry concealed weapons: When threatened, these species puncture their own skin with sharp bones in their toes, using the bones as claws capable of wounding predators.

The unusual defense mechanism is described by Harvard's David C. Blackburn, James Hanken, and Farish A. Jenkins, Jr., in a forthcoming issue of the journal Biology Letters.

"It's surprising enough to find a frog with claws," says Blackburn, a doctoral student in Harvard's Department of Organismic and Evolutionary Biology. "The fact that those claws work by cutting through the skin of the frogs' feet is even more astonishing. These are the only vertebrate claws known to pierce their way to functionality."

"Most vertebrates do a much better job of keeping their skeletons inside," he adds.

Blackburn first became aware of the clawed frogs while conducting fieldwork in the central African nation of Cameroon. When he picked up one of the hulking fist-sized frogs, it flailed its hind legs violently, scratching him and drawing blood.

Back in the U.S., Blackburn examined museum specimens of 63 African frog species. He noticed that in 11 species -- all in the genera Astylosternus, Trichobatracus, and Scotobleps and all native to central Africa -- the bones at the ends of the toes were pointed and hooked, with smaller, free-floating bones at their tips. Eventually he determined that these small nodules at the tips of the frogs' feet were connected to the rest of the toe by a collagen-rich sheath.

"These nodules are also closely connected to the surrounding skin by dense networks of collagen," Blackburn says. "It appears they hold the skin in place relative to these claw-like bones, such that when the frog flexes a certain muscle in the foot, the sharp bone separates from the nodule and bursts through the skin."

This claw-like structure is no conventional claw, though: It is pure bone, free of the keratin sheath that normally surrounds vertebrate claws. And unlike a claw that retracts into a specialized structure in an animal's foot, as in cats, the site where the frogs' foot bones emerge appears to be covered with ordinary skin.

While these frogs were mentioned in the scientific literature on a few occasions from 1900 to 1925, they are generally little-known in the U.S., appearing in few museum collections. Even the handful of researchers who wrote about them a century ago often misinterpreted the piercing of the skin as damage incurred during preservation of specimens.

The frogs are widely roasted and eaten in Cameroon, where hunters -- evidently well aware of the risk of injury -- go to great lengths to avoid handling them when alive.

"Cameroonian hunters will use long spears or machetes to avoid touching these frogs," Blackburn says. "Some have even reported shooting the frogs."

Of more than 5,500 known frog species, Blackburn and his colleagues found just 11 with claws, and speculate there may be another couple of similarly equipped species.

Blackburn plans to study live specimens of the African frogs to determine whether retraction of the foot bones back into the body is an active or a passive process, and how the damaged skin regenerates after the claws are deployed.

"We suspect, since the frog does suffer a fairly traumatic wound, that they probably use these claws infrequently, and only when threatened," Blackburn says.


'/>"/>

Contact: Steve Bradt
steve_bradt@harvard.edu
617-496-8070
Harvard University
Source:Eurekalert

Related biology news :

1. Many African-Americans have a gene that prolongs life after heart failure
2. Alcohol and malt liquor availability and promotion higher in African American inner cities
3. Marsupial lion tops African lion in fight to death
4. Study: weight-loss tips differ in African-American, mainstream magazines
5. Study of African traditional medicine will begin world-first clinical trial
6. New genetic variant associated with prostate cancer in African-Americans
7. Improving science, technology in Africa is aim as G-8, African, UN experts convene in Berlin
8. Newfound ancient African megadroughts may have driven the evolution of humans and fishes
9. Report: African, Asian, Latin American farm animals face extinction
10. Understanding hypertension in African Americans proves elusive
11. Adaptation to parasites drive African fishes along different evolutionary paths
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:4/5/2017)... , April 5, 2017 Today ... announcing that the server component of the HYPR platform ... for providing the end-to-end security architecture that empowers biometric ... HYPR has already secured over 15 million users ... including manufacturers of connected home product suites and physical ...
(Date:3/30/2017)... -- On April 6-7, 2017, Sequencing.com will host the world,s ... at Microsoft,s headquarters in Redmond, Washington ... health and wellness apps that provide a unique, personalized ... is the first hackathon for personal genomics and the ... the genomics, tech and health industries are sending teams ...
(Date:3/28/2017)... PUNE, India , March 28, 2017 ... (Analog, IP, Biometrics), Hardware (Camera, Monitors, Servers, Storage Devices), ... Maintenance), Vertical, and Region - Global Forecast to 2022", ... 30.37 Billion in 2016 and is projected to reach ... 15.4% between 2017 and 2022. The base year considered ...
Breaking Biology News(10 mins):
(Date:8/16/2017)... , Aug. 16, 2017  This year,s edition of the Inc. ... in life sciences workforce solutions, has made the list for the third ... recognizes the nation,s fastest-growing private companies based on a set of quantitative ... which includes the fastest-growing companies in the Bay State ... Inc. 5000 ...
(Date:8/15/2017)... ... August 15, 2017 , ... Kapstone Medical is proud to announce ... medical technology companies and inventors develop and safeguard their latest innovations. The company ... with a portfolio of clients in the United States and around the world. ...
(Date:8/15/2017)... ... August 15, 2017 , ... Any expert in stem cell research or stem ... more than half a century. Despite their essential roles in human health and ... that molecular tags developed for this purpose also tag other, more abundant, non-stem tissue ...
(Date:8/15/2017)... ... August 15, 2017 , ... Coffea arabica accounts ... and abiotic factors. During this educational webinar, participants will learn about the importance ... gain a better understanding of how genomics is important for coffee breeding improvement. ...
Breaking Biology Technology: