The difference and sensitivity of each cells is dependent upon the differences in the outer and inner segments. The synaptic pedicle communicates with other retinal cells. ![]() A nucleus lies beneath the region of the myoid and is connected to a synaptic pedicle via an axon. The inner segment may have any or all of the following: an oil droplet, an ellipsoid, a paraboloid, and a myoid. The outer segment connects to the inner segment by a ciliary stalk. The orientation and size of these disks determines whether the photoreceptor cell is a rod or a cone. The outer segment contains disks with photosensitive pigment molecules. The retina is composed of two segements, the outer segement and the inner segement. If the spectacle is not removed during ecdysis, this can lead to eye damage. Spectacles turn a light blue as it prepares to shed. During ecdysis, the spectacle sheds from the eye along with the rest of its skin. A scale that is actually part of the skin, a spectacle, protects the eyelids. Only two types of neurons are in this eye: photoreceptors and ganglion cells. This eye contains a cornea, lens, and retina like the lateral eyes, but it is simpler in structure. Some lizards and tuatara contain a third eye used for detecting changes in ambient light conditions, called a parietal eye, located on the top of their head. More than meets the eye: change in pupil shape by a mock viper Frontiers in Ecology and the Environment, 14 (8), 453-454 DOI: 10.1002/fee.While birds and most reptiles have a ring of bones around each eye that supports the eyeball (the sclerotic ring), crocodilians lack these bones, just like mammals and snakes. Silva, I., Crane, M., Artchawakom, T., Suwanwaree, P., & Strine, C. For animals that don't have super strength or speed, a less mild-mannered disguise might be just enough to let them survive another day. Another snake in this region, the Malayan bridle snake, mimics a venomous snake called the Malayan krait not just in its coloration, but by hiding its head under its coils when threatened. "Appearing dangerous might be a last resort, when all else fails," the authors write. If the snakes were just trying to hide, it would make sense to disguise their pupils sooner. But the researchers note that they only saw snakes change their pupils after a human touched them, and not when someone was merely nearby. Or maybe slit eyes are harder for predators to see by shrinking its pupil to a slit, a snake might make its head blend in better with its surroundings. For example, maybe shrinking their pupils improves mock vipers' vision during an attack. The authors think the mock viper may have evolved to mimic this snake. A visually oriented predator would likely have a hard time distinguishing the slit-eyed mock viper from a dangerous true viper. Mock vipers share their range in this part of the world with the similar-looking, but very venomous, Malayan pit viper. ![]() The authors think this ruse might help mock vipers defend themselves from hungry animals. But if a threatening animal (say, a human scientist) comes close enough, it squeezes its pupil into a slit. When the snake is relaxed, its pupil is round. They found that the mock viper does, in fact, have a shape-shifting pupil. Had someone made a mistake? Or did the mock viper have a trick up its non-sleeve that no one had noticed before? The researchers explored the question further by methodically spooking some snakes and observing their reactions. Thinking that he had picked up a viper, he instinctively dropped the animal, which immediately fled into the underbrush. However, as one team member grasped the snake behind the head, he noticed that the eyes had shifted to completely vertical slits. ![]() In the summer of 2012, researchers from Thailand's Sakaerat Environmental Research Station were doing fieldwork in a forest in northeastern Thailand when they came across a small reptile basking in the sun:Īsed on careful visual inspection we confirmed that the snake was in fact a mock viper because it had round pupils instead of the vertical slit pupils of true vipers. So imitating a more dangerous snake might help mock vipers scare off potential predators. Mock vipers carry only a mild venom they're harmless to humans, for example. Other details are different, though, such as the mock viper's round pupils. Like true vipers, mock vipers have triangular heads. Actual vipers are a widespread family of venomous snakes. It's common across much of Asia, and-as you might have guessed from its name-looks a lot like a viper. The mock viper ( Psammodynastes pulverulentus ) is mild-mannered, not superpowered. This makes it resemble a much more dangerous animal. One snake hides its identity using a similar trick: when threatened, it changes the shape of its pupils. Superman donned glasses to disguise himself and blend in with other people.
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