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Word of the Week: Nictate

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Welcome to Word of the Week! Stay tuned for a new word each week to amp up your nature vocabulary!

The word of the week is nictate [nik-teyt] (verb): to blink. This word has a special usage in the animal world to describe the nictating membrane — the third eyelid present in the eyes of some birds, fishes and other vertebrates.

This third eyelid is often a thin, transparent or translucent membrance that is used to keep the eyeball moist and clean while still maintaining vision — sort of like a windsheild wiper. Birds of prey, like the peregrine falcon, use it to clean out pollutants when traveling at high speeds.

The nictating membrane also offers protection to animals when fighting against other animals as they cannot afford any damage to their eyesight which is critical to their ability to survive and fend for themselves. Birds also use them to avoid any accidental damage to their eyes when feeding their chicks.

Do humans have a nictating membrane? No, but ever wondered what that little pink thing in the corner of our eyes are? This is said to be a vestigial remnant of what used to be a nectating membrane called the plica semilunaris. Much like our tailbones, the plica semilunaris too no longer serves its original purpose and is said to have disappeared long before anatomically modern humans came into being.

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