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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.
Naïve organisms initially produce a reflexive, unconditioned response (UR) (e.g. blink or extension of nictitating membrane) that follows US onset. After many CS-US pairings, an association is formed such that a learned blink, or conditioned response (CR), occurs and precedes US onset. [ 1 ]
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 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 ...
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.
A frog's ear drum works in very much the same way as does a human eardrum. It is a membrane that is stretched across a ring of cartilage like a snare drum that vibrates. Crossing the middle ear chamber there is an ossicle called the columella that is connected to the tympanum, and another ossicle, the operculum, that connects this to the oval ...
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 ]
The tabulated schema is used as the central organizing device in many animal behaviour, ethology, behavioural ecology and evolutionary psychology textbooks (e.g., Alcock, 2001). One advantage of this organizational system, what might be called the "periodic table of life sciences," is that it highlights gaps in knowledge, analogous to the role ...