17 簡介 在動物展示的多種現象中 — 由擬態、冬眠，到生物發 光 — 其中一種最吸引的是一些動物在眨眼間改變身體顏 色的能力。藉此牠們能避過捕食者的法眼，與同伴溝通，在 受威脅時恐嚇對方，以及調節身體溫度。 動物如何改變顏色？ 動物變色的過程涉及名為色素細胞的特化細胞。這些帶 顏色的細胞位於皮膚內，含有色素或光子 結構 [1]。色素吸收可見光中特定波長的 光，並反射那些沒有吸收到的波長，結果產 生我們所見的顏色。含色素的色素細胞以 其顏色命名，包括黑色素細胞（黑色或深 棕色）、藍色素細胞、黃色素 細胞等等。除了由色素構 成的顏色外，還有透過另一種 原理構成的結構色（structural colors）。在魚類、兩棲類和 爬蟲類找到的晶體細胞含有透 明的鳥嘌呤奈米晶體 [2]，它能 干涉（interfere）從皮膚表面反 射特定頻率的光 [3]。晶體細胞 亦能產生顏色隨觀察角度改變 的虹彩 [1]。 變色龍 變色龍眾所周知是變色動物的代表。 其他動物透過控制色素細胞的聚散變色， 而變色龍就有兩層晶體細胞加強對身體 顏色的控制 [2]。上層包含排列整齊的鳥 嘌呤奈米晶體。七彩變色龍（panther chameleons）可以透過增加細小晶體間 的距離控制光的干涉以改變顏色，使皮膚 由原本反射藍光變成反射波長較長的紅 光。雄性七彩變色龍會在雄性競爭或求偶 中被觸發，在黃色素細胞提供背景色下，將 身體顏色由整體的綠色變成黃或橙色。 下層包含對近紅外線（700– 1,400 nm）有 高反 射性的 雜亂鳥嘌呤晶體。 expand upon muscle contraction, increasing the area of exposure of the pigment, hence displaying a more intense skin color. Similar to chameleons, cephalopods also possess iridophores to modify their skin color through optical interference. By modifying the arrangement and molecular structure of reflectin proteins and expulsing water out of the cell, iridophores can be turned “on” and “off” as both actions can change their optical properties [1]. By selectively activating different groups of chromatophores and iridophores to mix different colors, the mimic octopus can accurately mimic the patterns of its surroundings, and change its morphology to imitate a wide variety of marine animals like flatfish, lionfish, and banded seasnakes [4]. In addition to chromatophores, the mimic octopus also utilizes other specialized skin cells called papillae to enhance its mimicry [5]. These papillae are small muscular structures that can change the threedimensional texture of the octopus’s skin, providing an added layer of deception. Conclusion The study of color-changing abilities in animals such as chameleons and octopuses, highlights the intricate mechanisms and adaptations in nature. Through studying these processes, we gain insight into the strategies of animal survival and communication, enhancing our knowledge and awareness of the value of biodiversity. Animals By Roshni Printer
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