#AtoZChallenge2020: Geckos

Theme: Natural Texas

“Geckos”

–Gecko on glass

Geckos are small lizards belonging to the infraorder Gekkota, found in warm climates throughout the world. They range from 1.6 to 60 centimeters (0.64 to 24 inches). Most geckos cannot blink, but they often lick their eyes to keep them clean and moist. They have a fixed lens within each iris that enlarges in darkness to let in more light.Geckos are unique among lizards for their vocalizations, which differs from species to species. Most geckos in the family Gekkonidae use chirping or clicking sounds in their social interactions, tokay geckos (Gekko gecko) are known for their loud mating calls, and some other species are capable of making hissing noises when alarmed or threatened. They are the most species-rich group of lizards, with about 1,500 different species worldwide. The New Latin gekko and English “gecko” stem from the Indonesian-Malay gēkoq, which is imitative of sounds that some species make.

All geckos except species in the family Eublepharidae lack eyelids; instead, the outer surface of the eyeball has a transparent membrane, the cornea. Species without eyelids generally lick their own corneas when they need to clear them of dust and dirt.

–Leopard gecko

–Gecko cleaning its eyeball

Nocturnal species have excellent night vision; their color vision in low light is 350 times more sensitive than human color vision. The nocturnal geckos evolved from diurnal species, which had lost the eye rods. The gecko eye, therefore, modified its cones that increased in size into different types, both single and double. Three different photo pigments have been retained and are sensitive to UV, blue, and green. They also use a multi-focal optical system that allows them to generate a sharp image for at least two different depths.

Like most lizards, geckos can lose their tails in defense, a process called autonomy. 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. Geckos are well known to people who live in warm regions of the world, where several species make their home inside human habitations. These (for example the house gecko) become part of the indoor menagerie and are often welcomed, as they feed on insects, including moths and mosquitoes. Unlike most lizards, geckos are usually nocturnal.

About 60 percent of gecko species have adhesive toe pads that allow them to adhere to most surfaces without the use of liquids or surface tension. Such pads have been gained and lost repeatedly over the course of gecko evolution.

The setae on the feet of geckos are also self-cleaning and usually remove any clogging dirt within a few steps. Teflon, which has very low surface energy, is more difficult for geckos to adhere to than many other surfaces.

In Texas, the two most common gecko species are the the Mediterranean house gecko, Hemidactylus turcicus, and the common house gecko, Hemidactylus frenatus. House geckos are common in suburban and urban areas.