Nature’s Amazing Wonder: The Gecko
The gecko, famous in some circles in car insurance commercials, is a very unique but average sized lizard. It is well known among biologists for its chirping vocalizations and its sophisticated adhesive toe pads that allow it to climb with ease up smooth vertical surfaces. Actually, the gecko’s ability to run vertically up and down at will has astonished almost everyone who has ever seen them, from Aristotle in the 4th century BC to today.
An amazing variety of geckos exist – African clawed gecko, African fat-tailed gecko, velvet gecko, cat geckos, and the dwarf gecko, to name a few popular breeds. The largest species is the tokay gecko and the most common gecko kept as a pet is the Leopard gecko. The Leopard gecko is docile and calm, has a very colourful yellow and black coat, and adapts well to captivity. It has claws, not foot pads, and for this reason it cannot walk up walls, but it can rapidly climb up rough surfaces such as rocks or tree bark.
Common variations include size, colour, skin texture, and the ability to climb walls and walk on ceilings. Almost every colour – from bright to dull – and numerous combinations and designs produce enormous gecko variety. A reptile, a gecko can live as long as 30 years, is typically 10 – 40 cm long, and periodically sheds its entire skin.
Some species can even regrow certain structures, such as the entire tail. If the animal is threatened, grabbed by the tail, or involved in a fight, it will drop its entire tail at specific break points. As soon as the tail is lost, rapid vasoconstriction occurs to reduce blood loss. The now-separated organ wiggles for a few minutes, often distracting the predator. The gecko then grows a whole new tail in only a few weeks time.
Around 2000 different species are now known. Most are arboreal and live in warm climates in Asia, southern Europe and North and South America. Some even live in people’s homes, entertaining the residents by walking upside down on their ceilings. They are often welcomed in homes as permanent guests because they feed on the many insect pests that thrive in hot, humid climates where geckos often live.
Their ability to walk on ceilings has mystified scientists and laypersons for decades. No known animal except the gecko has the required specialized toe foot pads that allow it to adhere to a wide variety of surfaces, including glass, without the use of liquids to serve as an adhesive. Scientists have only recently discovered how the gecko foot, which is “the most versatile and effective adhesive known” functions (Autumn et al. 2002. PNAS 99 #19 p. 12252).
The gecko’s secret is to use a chemical bond called van der Waals forces. These bonds form between the 500,000 microscopic hair-like setae on each foot and the surface to which they adhere. The setae split into 100 to1000 very fine mini-bristles to allow a high level of surface contact (Autumn et al. 2000. Nature 405: 681-684). At the end of each seta, the mini-bristles, about a billion in total, are enlarged to form flattened spoon-like endings called spatulae that look like suction cups (Forbes. 2006 The Gecko’s Foot. W. W. Norton p. 82). This design allows the foot to take the shape of the object it adheres to at the molecular level as does glue and adhesive tape. They both work the same way, allowing a strong bond to form.
Spatulae bond so strongly that they can hold about eight times the gecko’s weight. The only known common material that the setae cannot bond to is Teflon, a substance engineered to resist van der Waals forces. Each seta is so small that an opening the size of a human hair could hold from three to thirty of them. The setae are also self-cleaning, removing any clogging debris after a few short steps. The gecko breaks the van der Waals bond by peeling their toes from the surface from the tip inward, rapidly breaking a few of the van der Waals forces at a time until it is freed (Tian et al. 2006. PNAS 103 #51: 19320-19325).
Professor Kellar Autumn has studied geckos for most of his professional life, both in the lab and in the wild (Forbes, 2006 p. 79). One of his major findings is that their surefootedness is not their only talent. They have finely honed senses, including enormous eyes and excellent vision that enable them to hunt at night. They also have hearing so sensitive that they can sense an insect move on a wall twenty feet away (Forbes p. 81). Geckos also, unlike most other lizards, can vocalize, producing sounds that range from chirping like a bird to a loud barking like a dog.
Able to Change Colour
Certain gecko species can actually change their colour to match the environment or even their mood. By day their colour may be light, at night dark. A gray-brown colour in response to excitement may become dark-brown (Grzimek, 1975. Grzimek’s Animal Life Encyclopedia vol 6 Van Nostrand p. 166). The sudden colour change can be striking – one type can go from light olive-green to a velvety black-brown in a matter of seconds.
Another amazing trait of a species called Bynoe’s geckos is that it can change from a sexual organism and reproduce parthenogenetically (Kearney et al. 2005 Physiological and Biochemical Zoology 78 # 3: 316-324). In other words, it gives up sexual reproduction and uses cloning instead.
Evolution of the Sophisticated Toe
Although other animals, including beetles, flies, and spiders, have complex “biological attachment devices” allowing them to walk on vertical walls, only geckos have the sub-micro attachment devices. Setose or “hairy attachment systems” as well as all other biological attachment devices, are believed by evolutionists to have evolved independently, yet these devices are very similar and function in similar ways (Arzt et al. 2003 PNAS 100 #19: p. 10603). Some use fluids, others, such as geckos, use a dry system.
All known fossil geckos, including several excellent examples preserved in amber, are fully modern geckos with a fully developed “sophisticated adhesive mechanism” using setae (Arnold and Poinar. 2008. Zootaxa 1847: p. 62). One newly discovered example, well preserved in Burmese amber, was dated by evolutionists to the Lower Cretaceous – about 100 million years old, according to their estimates. The fossil includes fully modern setae on a juvenile about “50 million years older” than the previously oldest known gecko fossil (Arnold and Poinar p. 62, 67). Standish, for his part, concluded that the “narrow specification of the setae and their arrangement on gecko’s bodies makes evolutionary explanations of their origin problematic and is suggestive of design. This is the oldest known gecko fossil, suggesting that the very first geckos had the ability to perform the remarkable climbing feats we admire today.” (Standish. 2008.Origins 63:p. 40).
In spite of the investment of millions of dollars, modern research still has not been able to duplicate the gecko foot design. The closest we have come is MIT researchers who have, after extensive research, developed an anti-sliding adhesive that attempts to mimic the gecko. Ironically, geckos have long been considered evolutionarily primitive due to possessing many “primitive” traits, such as primitive notochord remnants, a primitive hyoid bone, and primitive scales (Grzimek p. 153). We now know that primitive they are not, but among the most advanced, and also amazing, life forms known.
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