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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.
The brille (also called the ocular scale, eye cap or spectacle) is the layer of transparent, immovable disc-shaped skin or scale covering the eyes of some animals for protection, especially in animals without eyelids.
This six-kingdom model is commonly used in recent US high school biology textbooks, but has received criticism for compromising the current scientific consensus. [13] But the division of prokaryotes into two kingdoms remains in use with the recent seven kingdoms scheme of Thomas Cavalier-Smith, although it primarily differs in that Protista is ...
The origin of the order name Anura—and its original spelling Anoures—is the Ancient Greek alpha privative prefix ἀν-(an-from ἀ-before a vowel) 'without', [6] and οὐρά (ourá) 'animal tail'. [7] meaning "tailless". It refers to the tailless character of these amphibians. [8] [9] [10] The origins of the word frog are uncertain and ...
The eyelids of a bird are not used in blinking. Instead the eye is lubricated by the nictitating membrane, a third concealed eyelid that sweeps horizontally across the eye like a windscreen wiper. [12] The nictitating membrane also covers the eye and acts as a contact lens in many aquatic birds when they are under water. [5]
The islands are difficult to get to, [107] and are colonised by few animal species, indicating that some animals absent from these islands may have caused tuatara to disappear from the mainland. However, kiore (Polynesian rats) had recently become established on several of the islands, and tuatara were persisting, but not breeding, on these ...
The irises of the eyes are golden to brown, and the transparent nictitating membrane is pale blue. The bill is black, with a blue cere, and the feet are white with black talons. [26] On the underside of the wings the wrists are black, which serves as a field mark. [30]
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 ...