Can Lizards See in Dark?
All lizards have retinas that possess photoreceptors containing multi-colored oleos droplets that separate out and distinguish the whole range of the color spectrum. Turtle retinas are the same, but in addition, lizards also have in the cones of their eyes, opsin proteins that allow them to see higher wavelengths in the UV range. As far as clarity goes, lizards can focus on far and nearby objects by either squeezing for distance or stretching for closeness their eye lens. They achieve this by utilizing the ciliary muscles (the part of the eye connecting the iris to the choroid) and annular pads (soft tissue surrounding the lens). However, nocturnal lizards have a larger pupillary, lens aperture, and cornea than do their diurnal kin. This improves the light-gathering ability for night vision but diminishes visual acuity. One aspect unique to lizard vision is that the choroid body, known as the CONUS papillary projects, out into the vitreous humor where it continually nourishes the cornea.
Lizards can use their senses of sight, touch, olfaction, and hearing the same as other vertebrates. The balance that varies with the habitat of different species; for instance, skinks that live largely covered by loose soil rely heavily on olfaction and touch, while geckos depend on acute vision for their ability to hunt their prey and to evaluate the distance to their prey before striking.
Lizards do not have external ears, having instead a circular opening in which the tympanic membrane (eardrum) can be seen.
All the lizards have a specialized olfactory system, the vomeronasal organ, used to detect pheromones. Some lizards transfer scent from the tip of their tongue to other organs; the tongue is used only for this information-gathering purpose and is not involved in manipulating food. Some lizards, especially iguanas, have retained a photosensory organ on the top of their heads called the parietal eye, a basal (“primitive”) feature also present in the tuatara. They have only a rudimentary retina and lens and cannot form images but are sensitive to any change in light and dark and can detect movement. This helps them detect predators.
In contrast to snakes, which largely experience the world through smell and taste, lizards are more visually oriented creatures. Lizards depend upon their vision for survival, and their eyes are well developed. A review of the evidence shows that most lizards can see color better than humans can; some will use color to communicate and make decisions, and some can even see colors in very dim light.
Night Vision in Lizards
Lizards can see very well in dark and color in dark or dim light. That means these geckos’ eyes are about 350 times more sensitive than human eyes, which see only black and white in the same conditions. Can evolution account for the origin of the remarkable machinery that enables these nocturnal creatures to see so well? Geckos also have a much higher density of oversized cone cells in their retinas that are responsible for detecting specific light wavelengths.
In their study published in the Journal of Vision, the researchers found that together, these zones and cones form a “multifocal optical system.” Furthermore, the refractive powers of their lens array “is of the same magnitude as needed to focus light of the wavelength range to which gecko photoreceptors are most sensitive.
“Thus, the various parts of this gecko’s eyes are finely tuned to work together, allowing the animal to sharply focus on at least two different depth fields at the same time. In addition to seeing color in the dark, the geckos have built-in correctional abilities for blurred images caused by longitudinal chromatic aberration, or the failure to focus all colors to the same point.
The authors of the study asserted that “at some point in evolution a group of lizards, the geckos, turned to a nocturnal lifestyle. In response to the demands of nocturnal vision without rods, the cones of nocturnal geckos have become much larger and more light-sensitive than those of their diurnal relatives.” However, there is no evidence that the mere presence of an environmental demand can cause the coordinated physiological changes required to bridge the differences between mono-focal eyes and this gecko’s multifocal, supersensitive eyes. Nor is there any evidence that mutations can do anything but corrupt existing genetic information, the opposite process to what is needed to invent the required whole sets of genetic material that specify the various interdependent parts that comprise these eyes.
Also, many creatures are successful night hunters without color vision.
This indicates that the night-time environment alone is an insufficient cause for developing these gecko eyes, which apparently did not “need” to exist for survival. Other nocturnal geckos have monofocal eyes the same as humans, and they have survived quite well without major changes.
There is strong evidence that evolution by mutations could not possibly build these amazing eyes. A more feasible explanation involves the creative power and genius of God, who on day six of the creation week implemented all of the design requirements for nocturnal helmet geckos with their specialized visual system.
The Lizard Eye
Lizards have characteristic vertebrate eyes, there pupil allows light to pass from a lens, which focuses the light on the back of the retina, where the light stimulates photoreceptive cells. The photoreceptive cells change the light impulse into an electrical impulse that is transmitted to and interpreted by, the brain. Vertebrates have two types of photoreceptive cells: rods, which detect light when levels are low; and cones to detect color. The cones contain pigments that filter the light hitting it, allowing animals to see a variety of colors. In some lizard species, some of their cones are calibrated for seeing ultraviolet light.
Nocturnal animals often see colors poorly but have good vision in low light. These animals often have eyes containing many rods and relatively few cones. Geckos are different, however, and see in dim light by using three sets of cones. A study demonstrated that helmeted geckos (Tarentola chazaliae) were able to discern grey and blue shades in light comparable to dim moonlight.
Many lizards have a third eye, located on the top of their heads. Termed the parietal eye, this eye is very simple, and its primary function is to determine light levels. Lizards are thought to use data from this parietal eye to influence basking behavior. Interestingly, a study demonstrated that the parietal eye of some lizards is even able to see two different colors: green and blue. It is possible that distinguishing between these colors allows the lizards to determine the time of day as the colors of daylight shift with the sun.
Color and Communication
Chameleons and anoles both exhibit remarkable adaptations that enable color-based communication. By adopting any of a species-specific subset of color patterns, chameleons can communicate aggression, dominance, submission, receptivity, and non-receptivity to other members of their species. Anoles identify conspecifics by a combination of head bobs and dewlap extensions. These dewlaps are often brightly colored and patterned, and anoles use them as flags to advertise their identity to nearby lizards.
Colour and Decision-Making
Besides species identification, anoles can use color to make decisions. A study seeking to understand decision-making ability in anoles was conducted by Manuel Leal and Brian Powell, of Duke University, presented anoles with two differently colored discs; under one of the discs was a mealworm a treat for an anole. In most cases, the anoles learned to check the appropriately colored disc for the tasty morsel first.
Lizards have very developed eye structures. They are able to see In colors and are developed to the extent that they can discern colors at very low light levels it night.
Lizard Habitats and Facts
|Lizard Type||Foods||Adult Size||Vivarium Type||Eggs||Temperament||Country Origin||Price|
|Ameiva||Insects||20 "||Tropical Woodland||2-8||Aggressive||Central, South America||$ 49.99|
|Alligator Lizard||Insects||20"||Semi- Aquatic||6-12||Aggressive||North America||$ 18|
|Asian Water Dragons||Carnivorous||40"||Tropical Woodlands||8-16||Aggressive||Asia||$ 18 - $ 80|
|Panther Chameleon||Insects||12"||Tropical Woodlands||30-50||Aggressive||Madagascar||$ 150 - $ 600|
|Jacksons Chameleon||Insects||14"||Temperate Woodlands||Up to 30 Live Young||Aggressive||East Africa||$ 75 - $175|
|Giant Day Gecko||Insects||10"||Tropical Woodlands||2||Aggressive||Madagascar||$ 79.99|
|Leopard Gecko||Insects||10"||Desert||2||Aggressive||Asia, India||$ 30 - $ 45|
|Tokay Gecko||Insects||14"||Tropical Woodland||2||Aggressive||Southeast Asia, New Guinea||$ 39.99|
|Blu Tongue Skink||Vegetarian||20"||Savannah||6-25||Aggressive||New Guinea, Australia||$ 150 - $ 649|
|Common Walled Lizard||Insects||8"||Savannah||3-8||Aggressive||Central Europe||$ 460 - $ 600|
|Green Lizard||Insects||16"||Savannah||6-20||Aggressive||Europe, Southern Asia||?|
|Green Iguana||Vegetarian||60"||Tropical Woodland||20-40||Aggressive||Central, South America||$ 39 - $ 55|
|Desert Iguana||Vegetarian||15"||Desert||3-10||Aggressive||USA, Mexico||$ 34.99|
|Six Lined Racerunner||Insects||11"||Savannah||4-6||Aggressive||USA||$ 29.99|
|Chinese Crocodile Lizard||Carnivorous||12"||Semi- Aquatic||2-12 Live Young||Aggressive||China||$ 1200|
|Collared Lizard||Insects||14"||Desert||4-24 Eggs||Aggressive||USA, Mexico||$ 53.99|
|Western Fence Lizard||Insects||9"||Savannah||6-13||Aggressive||USA||$ 19.99|
|Chuckwalla||Vegetarian||18"||Desert||6-13 eggs||Aggressive||Mexico||$ 88.99|
|Green Anole||Insects||9"||Tropical Woodland||2||Aggressive||Southern USA||$ 10.00|
|Brown Anole||Insects||8"||Tropical Woodland||2 Eggs||Aggressive||Caribbean, Central America||$ 3.99 - $ 7.99|
|Knight Anole||Insects||22"||Tropical Woodland||1-2||Aggressive||Cuba||$ 39.99|
|Nile Monitor||Carnivorous||79"||Savannah||10-60||Aggressive||Egypt||$ 69.99|
|Bosc's Monitor||Carnivorous||69"||Savannah||10-50||Aggressive||Central Africa||$ 100 - $ 150|
|Bearded Dragon||Insects||20"||Desert||15-30||Social||Australia||$ 60 - $ 400|
|Agama||Insects||16"||Savannah||10-20||Aggressive||North Africa||$ 24.99|
|Five Lined Skink||Insects||9"||Temperate Woodland||15||Aggressive||Africa||$ 10|
|Red Tailed Rock Lizard||Insects||8"||Savannah||2-4||Aggressive||South Africa||?|