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Some skates and rays have crescent shaped pupils, [16] gecko pupils range from circular, to a slit, to a series of pinholes, [17] and the cuttlefish pupil is a smoothly curving W shape. Although human pupils are normally circular, abnormalities like colobomas can result in unusual pupil shapes, such as teardrop, keyhole or oval pupil shapes ...
Another mechanism regulates focusing chemically and independently of these two, by controlling growth of the eye and maintaining focal length. In addition, the pupil shape can be used to predict the focal system being utilized. A slit pupil can indicate the common multifocal system, while a circular pupil usually specifies a monofocal system.
The black skimmer has an additional adaptation and is the only species of bird known to have slit-shaped pupils. [4] the forehead, ends of the secondaries, tail feathers and under parts are white, the rest of the plumage is black and the basal half of the bill is crimson. [5]
Most fish species seem to have a fixed pupil size, but elasmobranches (like sharks and rays) have a muscular iris which allows pupil diameter to be adjusted. Pupil shape varies, and may be e.g. circular or slit-like. [5] Lenses are normally spherical but can be slightly elliptical in some species.
They use the disadvantage of most prey animals' poor nocturnal vision to their advantage. The light receptors in crocodilians' eyes include cones and numerous rods, so it is assumed all crocodilians can see colours. [47] Crocodiles have vertical-slit shaped pupils, similar to those of domestic cats.
The tapetum lucidum, in animals that have it, can produce eyeshine, for example as seen in cat eyes at night. Red-eye effect, a reflection of red blood vessels, appears in the eyes of humans and other animals that have no tapetum lucidum, hence no eyeshine, and rarely in animals that have a tapetum lucidum. The red-eye effect is a photographic ...
The eyes of the octopus are large and at the top of the head. They are similar in structure to those of a fish, and are enclosed in a cartilaginous capsule fused to the cranium. The cornea is formed from a translucent epidermal layer; the slit-shaped pupil forms a hole in the iris just behind the cornea.
Goats have horizontal, slit-shaped pupils, allowing them to see well by both night and day, and giving them a wide field of vision on either side to detect predators, while avoiding being dazzled by sunlight from above. [20] Goats have no tear ducts. [21] Goats are ruminants.