Margaret Pye

Jun 11 2010, 12:38 AM

Well, they have no difficulty detaching their toes from surfaces when they want to.

http://en.wikipedia.org/wiki/Gecko#Gecko_toes:_setae_and_van_der_Waals_forces

 

Wikipedia]The toes of the gecko have a special adaptation that allows them to adhere to most surfaces
without the use of liquids or surface tension. Recent studies of the spatula tipped setae on
gecko footpads demonstrate that the attractive forces that hold geckos to surfaces are van
der Waals interactions between the finely divided setae and the surfaces themselves. Every
square millimeter of a gecko's footpad contains about 14,000 hair-like setae. Each seta has
a diameter of 5 micrometers. Human hair varies from 18 to 180 micrometers, so a human
hair could hold between 3 and 36 setae. Each seta is in turn tipped with between 100 and
1,000 spatulae.[4] Each spatula is 0.2 micrometer long[4] (one five-millionth of a meter), or
just below the wavelength of visible light.[5]

These van der Waals interactions involve no fluids; in theory, a boot made of synthetic setae
would adhere as easily to the surface of the International Space Station as it would to a
living room wall, although adhesion varies with humidity and is dramatically reduced under
water, suggesting a contribution from capillarity.[6] The setae on the feet of geckos are also
self cleaning and will usually remove any clogging dirt within a few steps.[4][7] Teflon, which
has very low van der Waals forces,[8] is the only known surface to which a gecko cannot
stick.[9] Geckos' toes seem to be "double jointed", but this is a misnomer. Their toes
actually bend in the opposite direction from our fingers and toes. This allows them to
overcome the van der Waals force by peeling their toes off surfaces from the tips inward. In
essence, this peeling action alters the angle of incidence between millions of individual
setae and the surface, reducing the Van der Waals force. Geckos' toes operate well below
their full attractive capabilities for most of the time. This is because there is a great margin
for error depending upon the roughness of the surface, and therefore the number of setae in
contact with that surface. If a typical mature 70 g (2.5 oz) gecko had every one of its setae in contact with a surface, it would be capable of
holding aloft a weight of 133 kg (290 lb):[10] each spatula can exert an adhesive force of 10 nanonewtons (0.0010 mgf).[6] Each seta can
resist 10 milligrams-force (100 µN), which is equivalent to 10 atmospheres of pull.[4]. This means a gecko can support about eight times its
weight hanging from just one toe on smooth glass. [4]

Margaret Pye

 

Ok, I stand corrected. Sorry about the confusion.

Toad of Spades

 

As for shedding, would they still retain the lepidosaurian method of shedding while having a complex body covering?