在海面下1000米的深處,，紅色波長的陽光無法到達這里,，從而使紅色的海洋生物能夠有效地“隱身”,。
然而事情在中間深度的海底區(qū)域——介于600米至1000米之間——卻變得棘手起來,，這里的陽光依然能夠悄然揭示五顏六色的海洋生物的輪廓,。
因此棲息在海洋中部的兩種頭足類動物——包括章魚和魷魚——就想出了一個巧妙的主意：開始時透明,，但是在某些食肉動物來到身邊時改變顏色,。
在11月10日發(fā)表在《當代生物學》雜志網(wǎng)絡(luò)版上的一項新研究中，美國杜克大學的海洋生物學家Sarah Zylinski和同事在章魚（Japetella heathi）和魷魚（Onychoteuthis banksii）中目睹了這種行為,。
他們將這兩種生物暴露在一束定向的藍光下,，就像這些光可能來自于某種發(fā)光的食肉動物，或是其他刺激一樣,，例如路過的陰影,。
研究人員發(fā)現(xiàn)，當藍光照到它們身上后,，這些頭足類動物會收縮肌肉,，從而拉伸其含有色素的細胞，并將皮膚變?yōu)榧t色,。
在野生環(huán)境中,，這種急速的“臉紅”會讓頭足類動物在它們的敵人面前消失，這是因為紅色的物體在藍光下幾乎是感覺不到的,。因此,，Japetella heathi和Onychoteuthis banksii便可以變得無影無蹤,，盡管它們實際上并不是透明的。
頭足類動物屬海洋動物,，魷魚,、章魚、船蛸,、鸚鵡螺和墨魚都是頭足類動物,。它們的身體多呈圓柱形，嘴長在身體下側(cè)的平面上,，生有尖利,、像鳥嘴一樣的顎，四周有可伸縮的強健觸須或手臂,。它們的眼睛發(fā)育很好,。頭足類動物是最大的無脊椎動物。（生物谷 Bioon.com）
doi:10.1016/j.cub.2011.10.014
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Mesopelagic Cephalopods Switch between Transparency and Pigmentation to Optimize Camouflage in the Deep
Sarah Zylinski, Sönke Johnsen
Animals in the lower mesopelagic zone (600—1,000 m depth) of the oceans have converged on two major strategies for camouflage: transparency and red or black pigmentation . Transparency conveys excellent camouflage under ambient light conditions, greatly reducing the conspicuousness of the animal's silhouette . Transparent tissues are seldom perfectly so, resulting in unavoidable internal light scattering . Under directed light, such as that emitted from photophores thought to function as searchlights , the scattered light returning to a viewer will be brighter than the background, rendering the animal conspicuous . At depths where bioluminescence becomes the dominant source of light, most animals are pigmented red or black, thereby reflecting little light at wavelengths generally associated with photophore emissions and visual sensitivities . However, pigmented animals are susceptible to being detected via their silhouettes . Here we show evidence for rapid switching between transparency and pigmentation under changing optical conditions in two mesopelagic cephalopods, Japetella heathi and Onychoteuthis banksii. Reflectance measurements of Japetella show that transparent tissue reflects twice as much light as pigmented tissue under direct light. This is consistent with a dynamic strategy to optimize camouflage under ambient and searchlight conditions.
