What Is Gecko?
Geckos are small to average sized lizards belonging to the family Gekkonidae, found in warm climates throughout the world. Geckos are unique among lizards in their vocalizations, making chirping sounds in social interactions with other geckos. An estimated 2,000 different species of geckos exist worldwide, with many likely yet to be discovered. The name stems from the Indonesian/Javanese word Tokek, inspired by the sound these animals make. The Malay word for gecko is cicak.
All geckos, excluding the Eublepharinae family, have no eyelids and instead have a transparent membrane which they lick to clean. Many species will, in defense, expel a foul-smelling material and feces onto their aggressors. There are also many species that will drop their tails in defense, a process called autotomy. Many species are well known for their specialized toe pads that enable them to climb smooth and vertical surfaces, and even cross indoor ceilings with ease (it is believed that the van der Waals force may contribute to this capability). These antics are well-known to people who live in warm regions of the world, where several species of geckos make their home inside human habitations. These species (for example the House Gecko) become part of the indoor menagerie and are often welcome guests, as they feed on insects, including mosquitoes.
The largest species, Delcourt’s gecko, is only known from a single, stuffed specimen found in the basement of a museum in Marseille, France. This gecko was 60 cm long and it was native to New Zealand. It was probably wiped out along with much of the native fauna of these islands at the end of the 19th century, when new predators were introduced there. The smallest gecko, the Jaragua Sphaero, is a mere 16 mm long and was discovered in 2001 on a small island off the coast of the Dominican Republic.
Geckos come in various colors and patterns such as purple pink blue. . Some are subtly patterned and somewhat rubbery looking, while others are brightly colored. Some species can change color to blend in with their environment or with particular temperatures. Some species are parthenogenic, which means the female is capable of reproducing without copulating with a male. This improves the gecko’s ability to spread to new islands. However, in a situation where a single female gecko populates an entire island, said island will suffer from a lack of genetic variation within the geckos that inhabit it. Geckos also make a quality pet for small households. They can live and breed in small tanks or Terrariums. They must have proper livng space to survive. The average temperature in the day should be between 78-88 degrees Fahrenheit (25-31 degrees Celsius) and at night temperatures should not go below 72 degrees Fahrenheit (22 degrees Celsius) inside the tank. Proper foods for the geckos range from small baby crickets, to green vegetables such as lettuce and cabbage. Packaged food can also be a good substitute
Gecko toes: setae and van der Waals forces
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. Each spatula is 0.2 micrometers long (200 billionths of a meter), or just below the wavelength of visible light
These van der Waals interactions involve no fluids; in theory, a boot made of synthetic setae would adhere as easily to the surface of theInternational 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. The setae on the feet of geckos are also self cleaning and will usually remove any clogging dirt within a few steps. Teflon, which has very low van der Waals forces, is the only known surface to which a gecko cannot stick. 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): each spatula can exert an adhesive force of 10 nanonewtons (0.0010 mgf). Each seta can resist 10 milligrams-force (98 µN), which is equivalent to 10 atmospheres of pull.. This means a gecko can support about eight times its weight hanging from just one toe on smooth glass
A study from Lund University proved that nocturnal geckos such as the helmet gecko, Tarentola chazaliaei, discriminate colors in dim moonlight when humans are color blind. The sensitivity of the helmet gecko eye was calculated to be 350 times higher than human cone vision at the color vision threshold. The optics in the gecko’s eyes, having distinct concentric zones of different refractive powers that constitute a multifocal optical system, together with the large cones of the gecko, are important reasons why they can use color vision at low light intensities. Although the intraspecific variation is large, in most of the individuals studied the concentric zones differed by 15diopters. This is of the same magnitude as needed to focus light of the wavelength range to which gecko photoreceptors are most sensitive. In contrast, the optical system of a different day gecko species showed no signs of distinct concentric zones and is therebymonofocal. Another feature of the nocturnal geckos – and other lizards – in which they differ from most other vertebrates is that they only have cones in their retina.
- subfamily Aeluroscalabotinae
- single genus Aeluroscalabotes, only one species A. felinus, Southeast Asia
- subfamily Diplodactylinae
- 16 genera, found in Oceania
- subfamily Eublepharinae
- 5 genera
- subfamily Gekkoninae
- subfamily Teratoscincinae
- single genus Teratoscincus (7 species)