貓科動物舌頭的微觀結構如何幫助它們保持皮毛潔淨
T.S.艾略特（T.S. Eliot）筆下神秘的貓咪麥卡維蒂（Macavity）除了是個能夠逃脫英國執法部門聯合行動的慣犯，還有一身「因疏於清潔而髒兮兮」的皮毛。它的犯罪行徑倒還能理解，髒皮毛着實讓人難以想象。真正的貓可都是美容專家。
家貓每天屈尊醒着的十個小時中，有四分之一花在清理身上的污垢、跳蚤、血和脫落的貓毛上。在專門負責清潔任務的貓舌上，覆蓋着成百上千個角蛋白倒刺。但直到現在，人們才弄明白這些被稱為絲狀乳突的錐狀突起究竟是如何賦予了貓科動物如此精通清潔的本領。
為瞭解開謎底，亞特蘭大佐治亞理工學院的工程專家亞歷克西斯·諾埃爾（Alexis Noel）和胡立德（David Hu）探究了家貓、短尾貓、雪豹和獅子等六種貓科動物的清潔梳理機制。研究活體動物的舌頭在口腔內的活動難度太大，所以兩人打造了一台自動梳理機，裝上了貓科動物的舌頭和皮毛。這些器官的主人已經在田納西州的老虎安息所（Tiger Haven）等收容大型貓科動物的養老院里去世。兩人把舌頭裝到機械臂上，讓它們去「舔」毛皮，並用高分辨率相機和掃瞄儀拍下照片。
兩位研究人員發現，絲狀乳突並非像人們以前所想的那樣是實心錐體，而是形似微小的勺子。每個絲狀乳突的頂端都有一個小溝槽，研究團隊將其命名為腔乳突。
這種結構通過表面張力將唾液從貓嘴中吸出，並將其釋放到皮毛最深處。每舔一次，就會轉移走舌頭上約一半的唾液。唾液起到多用途清潔劑的作用。而在舌頭收回時，腔乳突還能幫助吸收任何需要去除的污垢或血。因此，貓的舌頭「兼具絲瓜絡和海綿塊的作用」，胡立德說。
兩人的研究結果剛剛發表在《美國科學院院刊》上，可能會啟發人們研究出清潔復雜多毛表面的新方法。兩位研究人員自己展示了這類應用的一種，他們稱之為TIGR刷（Tongue-inspired Grooming brush，即「仿貓舌清理刷」）。他們用3D打印製造出形似貓舌乳突的結構，嵌在硅膠基墊上。TIGR刷梳理貓毛時拉扯貓皮毛的力度比現有的刷子更輕，也更容易清潔。這種刷子還可以將藥物塗抹在貓的皮毛深處或皮膚上，也就避免了通常需要先剃掉貓毛這個叫人煩惱的操作了。
How the microscopic structure of a cat』s tongue helps keep its fur clean
T.S. ELIOT』S MYSTERY cat, Macavity, besides being a criminalmastermind able to evade the combined ranks of British law enforcement, had a coat that was 「dusty from neglect」. Criminality is one thing, but this trulystrains the imagination. Real cats are champion groomers.
Of the ten hours a day that a domestic cat deigns to remain awake, it spends a quarter licking dirt, fleas, blood and loose hairs from its fur. Cats』 tongues, specialized for this task, are covered in hundreds of backward-facingkeratin spines. But exactly how these cone-shaped protuberances, calledfiliform papillae, work to give the animals such mastery over their cleanliness has remained unknown until now.
To crack the mystery Alexis Noel and David Hu, a pair of engineers at the Georgia Institute of Technology, in Atlanta, examined the grooming mechanisms of six feline species—from domestic pets and bobcats to snow leopards and lions. Studying the activity of tongues inside the mouths of living creatures proved tricky, so instead Dr. Noel and Dr. Hu built an automated grooming machine fitted out with tongues and furs from animals whose lives had ended at places such as the Tiger Haven in Tennessee, a sort of retirement home for rescued big cats. They attached the tongues to a mechanical arm and made them 「lick」 the furs. High-resolution cameras and scanners took pictures.
The two researchers found that the filiform papillae were shaped not, as had previously been thought, like solid cones. Rather, they resembled tiny scoops. Each had a small groove—named a cavo papilla by the team—at its tip.
This structure permits surface tension to wick saliva from a cat』s mouth and release it into the farthest recesses of the animal』s fur. During each lick, about half of the saliva on the tongue is so transferred. Saliva serves as a multi-purpose cleaning agent and the cavo papillae also assist the absorption, for the return journey, of any dirt or blood that needs removing. The cat』s tongue therefore 「acts like a loofah and a sponge at the same time」, says Dr. Hu.
The pair』s findings, just published in the Proceedings of the National Academy of Sciences, could inspire new ways to clean complex hairy surfaces. The authors themselves demonstrated one such application, which they call the tongue-inspired grooming (TIGR) brush. To make this they employed 3D printing to create structures, shaped like cat papillae, attached to a silicone base. The TIGR brush pulled on cat hairs and fur with less force than existing brushes, and was easier to clean. Such a brush could also be used to spread medicines deep into a cat』s fur or onto its skin, without the usual distressing practice of having to shave the animal first.
來源：辣椒英語
