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The nictitating membrane of a masked lapwing as it closes over the left eye, originating from the medial canthus. 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.
It is loose, thus eye movements are not restricted by it. Only one species of primate, the Calabar angwantibo, is known to have a functioning nictitating membrane. [4] With ocular allergies, the lacrimal caruncle and plica semilunaris may be inflamed and pruritic (itchy) due to histamine release in the tissue and tear film.
Ground sharks, like this blacknose shark, have a nictitating membrane which can be drawn over the eye to protect it. Carcharhiniformes / k ɑːr k ə ˈ r aɪ n ɪ f ɔːr m iː z /, commonly known as Ground Sharks, are the largest order of sharks, with over 270 species. They include a number of common types, such as catsharks, swellsharks, and ...
It is the vestigial remnant of the nictitating membrane, i.e., third eyelid, an organ that is fully functional in some other species of mammals. [43] Its associated muscles are also vestigial. [10] Only one species of primate, the Calabar angwantibo, is known to have a functioning nictitating membrane. [44]
The Harderian gland is a gland found within the eye's orbit that occurs in tetrapods (reptiles, amphibians, birds and mammals) that possess a nictitating membrane. [1] The gland can be compound tubular or compound tubuloalveolar, and the fluid it secretes (mucous, serous or lipid) varies between different groups of animals.
Cherry eye is typically diagnosed by examination of the conjunctiva and nictitating membrane. [2] The most obvious symptom of cherry eye is a round fleshy mass in the medial canthus of the eye, similar in appearance to the fruit it is named for. [ 8 ]
Rather heavily built, the bignose shark has a long, broad, and blunt snout with the nostrils preceded by well-developed, triangular flaps of skin. The moderately large, circular eyes are equipped with nictitating membranes (protective third eyelids). The mouth is broadly curved and lacks obvious furrows at the corners.
When under water, crocodile have a “third eyelid” called a nictitating membrane, which is present in many other reptiles, but is unique in crocodiles because it is semitransparent and acts as goggles to improve eyesight when hunting and prevents eye damage. Crocodiles are able to make certain sounds, especially juveniles.