scholarly journals Wet but not slippery: boundary friction in tree frog adhesive toe pads

2006 ◽  
Vol 3 (10) ◽  
pp. 689-697 ◽  
Author(s):  
W Federle ◽  
W.J.P Barnes ◽  
W Baumgartner ◽  
P Drechsler ◽  
J.M Smith
Keyword(s):  
Boundary Friction ◽  
Tree Frog ◽  
Force Measurements ◽  
Present Evidence ◽  
Laser Tweezer ◽  
Viscous Forces ◽  
Litoria Caerulea ◽  
Filled Joint ◽  
Tree Frogs ◽  
Close Contacts

Tree frogs are remarkable for their capacity to cling to smooth surfaces using large toe pads. The adhesive skin of tree frog toe pads is characterized by peg-studded hexagonal cells separated by deep channels into which mucus glands open. The pads are completely wetted with watery mucus, which led previous authors to suggest that attachment is solely due to capillary and viscous forces generated by the fluid-filled joint between the pad and the substrate. Here, we present evidence from single-toe force measurements, laser tweezer microrheometry of pad mucus and interference reflection microscopy of the contact zone in Litoria caerulea , that tree frog attachment forces are significantly enhanced by close contacts and boundary friction between the pad epidermis and the substrate, facilitated by the highly regular pad microstructure.

scholarly journals When the going gets rough – studying the effect of surface roughness on the adhesive abilities of tree frogs

2016 ◽  
Vol 7 ◽  
pp. 2116-2131 ◽  
Author(s):  
Niall Crawford ◽  
Thomas Endlein ◽  
Jonathan T Pham ◽  
Mathis Riehle ◽  
W Jon P Barnes
Keyword(s):  
Surface Roughness ◽  
Real Contact Area ◽  
Small Scale ◽  
Tree Frog ◽  
Natural Habitats ◽  
Litoria Caerulea ◽  
Frictional Forces ◽  
Tree Frogs ◽  
Air Pockets ◽  
Effect Of Surface

Tree frogs need to adhere to surfaces of various roughnesses in their natural habitats; these include bark, leaves and rocks. Rough surfaces can alter the effectiveness of their toe pads, due to factors such as a change of real contact area and abrasion of the pad epithelium. Here, we tested the effect of surface roughness on the attachment abilities of the tree frog Litoria caerulea. This was done by testing shear and adhesive forces on artificial surfaces with controlled roughness, both on single toe pads and whole animal scales. It was shown that frogs can stick 2–3 times better on small scale roughnesses (3–6 µm asperities), producing higher adhesive and frictional forces, but relatively poorly on the larger scale roughnesses tested (58.5–562.5 µm asperities). Our experiments suggested that, on such surfaces, the pads secrete insufficient fluid to fill the space under the pad, leaving air pockets that would significantly reduce the Laplace pressure component of capillarity. Therefore, we measured how well the adhesive toe pad would conform to spherical asperities of known sizes using interference reflection microscopy. Based on experiments where the conformation of the pad to individual asperities was examined microscopically, our calculations indicate that the pad epithelium has a low elastic modulus, making it highly deformable.

scholarly journals Adhesion and Detachment of the Toe Pads of Tree Frogs

1991 ◽  
Vol 155 (1) ◽  
pp. 103-125 ◽  
Author(s):  
GAVIN HANNA ◽  
W. JON ◽  
W. P. JON BARNES
Keyword(s):  
Vertical Surface ◽  
Natural Consequence ◽  
Shear Forces ◽  
Wet Adhesion ◽  
Viscous Forces ◽  
Osteopilus Septentrionalis ◽  
Filled Joint ◽  
Forward Locomotion ◽  
Tree Frogs ◽  
Adhesive Forces

The mechanisms by which the toe pads of tree frogs adhere to and detach from surfaces during climbing have been studied in Osteopilus septentrionalis and other tree frogs using a variety of techniques. The experiments on attachment lend general support to the theory that toe pads stick by wet adhesion. First, the presence of a meniscus surrounding the area of contact shows that pad and surface are connected by a fluid-filled joint. Second, experiments on single toe pads of anaesthetised frogs demonstrate that the pads exhibit the velocity-dependent resistance to shear forces expected of any system employing a fluid as an adhesive mechanism. Third, the largest adhesive forces that toe pads can generate (approx. 1.2mNmm−2, calculated from data on sticking ability) are within the range that can be produced by wet adhesion. Simple measurements of the forces needed to separate a pair of metal discs joined by mucus demonstrate that both viscous forces (Stefan adhesion) and surface tension (the two components of wet adhesion) are likely to play significant roles in the tree frog's adhesive mechanism. The experiments on detachment demonstrate that toe pads are detached from surfaces by peeling, the pads being removed from the rear forwards during forward locomotion up a vertical surface. When the frogs were induced to walk backwards down this vertical slope, peeling occurred from the front of the pad rearwards. Use of a force platform to measure directly the forces exerted by the feet during climbing shows that, during forward locomotion up a vertical slope, this peeling is not accompanied by any detectable detachment forces. Such forces of detachment are seen, however, during backward walking down the slope and when belly skin comes into contact with the platform. That peeling occurs automatically during forward locomotion is supported both by observations of peeling in single toe pads of anaesthetised frogs and by the inability of frogs to adhere to vertical surfaces in a head-down orientation. Indeed, frogs on a rotating vertical surface were observed to adjust their orientations back towards the vertical whenever their deviation from the vertical reached 85.1 ±21.5°. During forward locomotion peeling seems to occur as a natural consequence of the way in which the toes are lifted off surfaces from the rear forwards, while during backward locomotion it is an active process involving the distal tendons of the toes. Note: To whom requests for offprints should be send.

Morphologic, Immunohistochemical, and Molecular Characterization of a Novel Lankesterella Protozoan in Two White's Tree Frogs (Litoria caerulea)

2010 ◽  
Vol 41 (2) ◽  
pp. 242-248 ◽  
Author(s):  
Barbara Gericota ◽  
Michael M. Garner ◽  
Bradd Barr ◽  
Robert Nordhausen ◽  
R. Scott Larsen ◽  
...  
Keyword(s):  
Molecular Characterization ◽  
Litoria Caerulea ◽  
Tree Frogs

The valid nomen for the tree frog (genus Hyla) of Tunisia and Eastern Algeria

Zootaxa ◽  
2020 ◽  
Vol 4759 (4) ◽  
pp. 597-599 ◽  
Author(s):  
CHRISTOPHE DUFRESNES ◽  
PIERRE-ANDRÉ CROCHET
Keyword(s):  
Mediterranean Basin ◽  
Western Mediterranean ◽  
Northern Italy ◽  
Tree Frog ◽  
Rad Sequencing ◽  
Western Mediterranean Basin ◽  
Genome Wide ◽  
Genome Wide Data ◽  
Tree Frogs ◽  
Eastern Algeria

Mediterranean tree frogs, Hyla gr. meridionalis Boettger, 1874 (Anura: Hylidae) are widespread around the Western Mediterranean Basin, where they naturally occur across the Maghreb (Morocco, Algeria, Tunisia). Individuals of diverse Moroccan origins have been introduced and have expanded throughout the Iberian Peninsula, southern France and northern Italy (Liguria), but also on the Canary and Balearic archipelagos (Recuero et al. 2007; Dufresnes et al. 2019). Early molecular studies uncovered several mitochondrial lineages and suggested a major cryptic diversification within this taxon, with Tunisian and eastern Algerian (Numidia) populations carrying deeply divergent haplotypes compared with the rest of the range (Recuero et al. 2007; Stöck et al. 2008; Stöck et al. 2012). While intron markers showed little differentiation (Stöck et al. 2008; Stöck et al. 2012), genome-wide data obtained from RAD-sequencing have supported the deep split suspected from mtDNA (Dufresnes et al. 2018). 

CHLORAMPHENICOL WITH FLUID AND ELECTROLYTE THERAPY CURES TERMINALLY ILL GREEN TREE FROGS (LITORIA CAERULEA) WITH CHYTRIDIOMYCOSIS

2012 ◽  
Vol 43 (2) ◽  
pp. 330-337 ◽  
Author(s):  
Sam Young ◽  
Rick Speare ◽  
Lee Berger ◽  
Lee F Skerratt
Keyword(s):  
Terminally Ill ◽  
Litoria Caerulea ◽  
Tree Frogs

scholarly journals Cutaneous Chytridiomycosis in Poison Dart Frogs (Dendrobates spp.) and White's Tree Frogs (Litoria Caerulea)

1999 ◽  
Vol 11 (2) ◽  
pp. 194-199 ◽  
Author(s):  
Allan P. Pessier ◽  
Donald K. Nichols ◽  
Joyce E. Longcore ◽  
Melvin S. Fuller
Keyword(s):  
Litoria Caerulea ◽  
Tree Frogs

Anesthetic Efficacy of MS-222 in White's Tree Frogs (Litoria caerulea)

2020 ◽  
Vol 30 (1) ◽  
pp. 38
Author(s):  
Ashley R. Krisp ◽  
Jennifer C. Hausmann ◽  
Kurt K. Sladky ◽  
Christoph Mans
Keyword(s):  
Litoria Caerulea ◽  
Tree Frogs
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