在海面下1000米的深处，红色波长的阳光无法到达这里，从而使红色的海洋生物能够有效地“隐身”。
然而事情在中间深度的海底区域——介于600米至1000米之间——却变得棘手起来，这里的阳光依然能够悄然揭示五颜六色的海洋生物的轮廓。
因此栖息在海洋中部的两种头足类动物——包括章鱼和鱿鱼——就想出了一个巧妙的主意：开始时透明，但是在某些食肉动物来到身边时改变颜色。
在11月10日发表在《当代生物学》杂志网络版上的一项新研究中，美国杜克大学的海洋生物学家Sarah Zylinski和同事在章鱼（Japetella heathi）和鱿鱼（Onychoteuthis banksii）中目睹了这种行为。
他们将这两种生物暴露在一束定向的蓝光下，就像这些光可能来自于某种发光的食肉动物，或是其他刺激一样，例如路过的阴影。
研究人员发现，当蓝光照到它们身上后，这些头足类动物会收缩肌肉，从而拉伸其含有色素的细胞，并将皮肤变为红色。
在野生环境中，这种急速的“脸红”会让头足类动物在它们的敌人面前消失，这是因为红色的物体在蓝光下几乎是感觉不到的。因此，Japetella heathi和Onychoteuthis banksii便可以变得无影无踪，尽管它们实际上并不是透明的。
头足类动物属海洋动物，鱿鱼、章鱼、船蛸、鹦鹉螺和墨鱼都是头足类动物。它们的身体多呈圆柱形，嘴长在身体下侧的平面上，生有尖利、像鸟嘴一样的颚，四周有可伸缩的强健触须或手臂。它们的眼睛发育很好。头足类动物是最大的无脊椎动物。（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.
