"Third eyelid" of some animals that protects and moistens the eye while maintaining vision
The nictitating membrane of a masked lapwing as it closes over the left eye, originating from the medial canthusSlow motion video of a common buzzard yawning while perched on an antenna, with nictitating membrane visible (deployed asynchronously on left and right eye).
The nictitating membrane (from Latin nictare, to blink) is a transparent or translucent third eyelid present in some animals that can be drawn across the eye from the medial canthus to protect and moisten it while maintaining vision. All Anura[1] (tailless amphibians), and some reptiles, birds, and sharks have full nictitating membranes; in many mammals, a small, vestigial portion of the nictitating membrane remains in the corner of the eye. Some mammals, such as cats, beavers, polar bears, seals and aardvarks, have full nictitating membranes. Often called a third eyelid or haw, it may be referred to in scientific terminology as the plica semilunaris, membrana nictitans, or palpebra tertia.
^Rolleston, George; Jackson, William Hatchett (1898). Forms of Animal Life : A Manual of Comparative Anatomy, with Descriptions of Selected Types. Clarendon Press. p. 401.
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The nictitatingmembrane (from Latin nictare, to blink) is a transparent or translucent third eyelid present in some animals that can be drawn across the...
translucent third eyelid called a nictitatingmembrane, while others have a vestigial nictitatingmembrane. The membrane works to protect and moisten the...
generally characterized by lacking traits such as an anal fin, nictitatingmembrane, or suborbital shelves in the cranium. Squalomorphii sharks are also...
Cherry eye is a disorder of the nictitatingmembrane (NM), also called the third eyelid, present in the eyes of dogs and cats. Cherry eye is most often...
by the nictitatingmembrane, a third concealed eyelid that sweeps horizontally across the eye like a windscreen wiper. The nictitatingmembrane also covers...
found in other animals, some of which may have a third eyelid, or nictitatingmembrane. A vestige of this in humans survives as the plica semilunaris. The...
eyeball, restricting movement. It is the vestigial remnant of the nictitatingmembrane (the "third eyelid") which is drawn across the eye for protection...
patella, hip dysplasia, and Legg-Calvé-Perthes disease. Prolapsed nictitatingmembrane gland is also common in puggles despite not being prevalent in either...
with vertical slits. They do not have a true eyelid, but rather a nictitatingmembrane that allows light to enter the eye so that they will awaken when...
especially in animals without eyelids. In squamate reptiles both the nictitatingmembrane and the eyelids have been suggested as the evolutionary origin of...
Instead the eye is lubricated by the nictitatingmembrane, a third eyelid that moves horizontally. The nictitatingmembrane also covers the eye and acts as...
tetrapods (reptiles, amphibians, birds and mammals) that possess a nictitatingmembrane. The gland can be compound tubular or compound tubuloalveolar, and...
the inside corner of the eye. It is the vestigial remnant of the nictitatingmembrane, i.e., third eyelid, an organ that is fully functional in some other...
shark. Members of this order are characterized by the presence of a nictitatingmembrane over the eye, two dorsal fins, an anal fin, and five gill slits....
Pertaining to the nostrils. nasoral Between the nostrils and mouth. nictitatingmembrane An inner eyelid. notochord A rudimentary of embryonic spinal column...
rather than representing true trichromatic vision. Cats also have a nictitatingmembrane, allowing them to blink without hindering their vision. The domestic...
common in the crossbreed than both of the parent breeds. Prolapsed nictitatingmembrane gland is a condition more common in the Puggle and Jug than both...
rodents in the dark. Most reptiles, as well as birds, possess a nictitatingmembrane, a translucent third eyelid which is drawn over the eye from the...
may form a part of the courtship display, such as in weaver birds. nictitatingmembrane Also, third eyelid. A transparent or translucent third eyelid that...
species, like other dippers, is equipped with an extra eyelid called a nictitatingmembrane that allows it to see underwater, and scales that close its nostrils...
sensitivity to this part of the spectrum. Cats have a third eyelid, the nictitatingmembrane, which is a thin cover that quickly closes from the side when the...
sharks. Members of this order are characterized by the presence of a nictitatingmembrane over the eyes, two dorsal fins, an anal fin, and five gill slits...
flatworm Oculotrema hippopotami infests hippopotamus eyes, mainly the nictitatingmembrane. It is the only monogenean species (which normally live on fish)...
comparable to human eyelashes. Eagles have a third eyelid also known as a nictitatingmembrane, which "grows in the inner corner of the eye, next to the tear duct"...
Male portrait Female portrait Just after a dive - showing clear nictitatingmembrane In flight over Rideau River, Ottawa, Ontario With a northern crayfish...
sharks. Members of the orders are characterized by the presence of a nictitatingmembrane over the eye, two dorsal fins, an anal fin, and five gill slits....
eyelid known as a nictitatingmembrane, whereas most other primates have a lesser developed plica semilunaris. The nictitatingmembrane keeps the cornea...
usually possess spines, they usually have a sharp head, no anal fin or nictitatingmembrane, and five to seven gill slits. In most other respects, however, they...
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