Polaro-cryptic mirror of the lookdown as a biological model for open ocean camouflage
Polaro-cryptic mirror of the lookdown as a biological model for open ocean camouflage
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DOI：
10.1073/pnas.1222125110
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发表时间：
2013-06-11
影响因子：
11.1
通讯作者：
Cummings, Molly E.
中科院分区：
文献类型：
--
作者：
Brady, Parrish C.;Travis, Kort A.;Cummings, Molly E.
在3D空间中，由于没有隐藏的物体，开阔的海洋对伪装来说是一个具有挑战性的环境。用于反射加密的传统策略(例如，标准镜)对于与高太阳高度相关联的轴对称辐射场是有效的，而对于与低太阳倾斜度相关联的不对称偏振辐射场是无效的。在这里，我们确定了一个极化加密的生物模型。我们利用偏振成像技术和模拟外海偏振伪装技术测量了活体开阔海鱼(Lookdown，Selene Vmer)和海草栖息鱼类(Pinfish，Lagodon Rombodes)的表面反射率Mueller矩阵。俯视占据了我们的偏振对比度空间的最小化范围，而平底镜和标准镜面的测量显示出比最佳对比度更高的对比度。与垂直镜等非偏振敏感策略相比，向下反射策略在偏振加密方面获得了显著的收益(高达80%)。俯视通过利用入射照明改变反射属性(由16个穆勒矩阵元素m(Ij)描述)来实现在太阳高度上的极化加密。向下看保持反射极化与主轴对齐(背腹和前后，m(22)=0.64)，而随机化入射极化与主轴成45度(m(33)=-0.05)。这些反射特性允许俯视反映由于主轴和太阳的对准而与正午条件相关联的偏振度和偏振角的统一程度，并在与较低太阳海拔相关联的不对称光场中反映更复杂的偏振图案。我们的结果表明，极化隐蔽策略因栖息地而异，需要特定于背景的去极化和角度变化，以便在复杂的开放海洋环境中有效隐藏。
With no object to hide behind in 3D space, the open ocean represents a challenging environment for camouflage. Conventional strategies for reflective crypsis (e.g., standard mirror) are effective against axially symmetric radiance fields associated with high solar altitudes, yet ineffective against asymmetric polarized radiance fields associated with low solar inclinations. Here we identify a biological model for polaro-crypsis. We measured the surface-reflectance Mueller matrix of live open ocean fish (lookdown, Selene vomer) and seagrass-dwelling fish (pinfish, Lagodon rhomboides) using polarization-imaging and modeling polarization camouflage for the open ocean. Lookdowns occupy the minimization basin of our polarization-contrast space, while pinfish and standard mirror measurements exhibit higher contrast values than optimal. The lookdown reflective strategy achieves significant gains in polaro-crypsis (up to 80%) in comparison with nonpolarization sensitive strategies, such as a vertical mirror. Lookdowns achieve polaro-crypsis across solar altitudes by varying reflective properties (described by 16 Mueller matrix elements m(ij)) with incident illumination. Lookdowns preserve reflected polarization aligned with principle axes (dorsal-ventral and anterior-posterior, m(22) = 0.64), while randomizing incident polarization 45 degrees from principle axes (m(33) = -0.05). These reflectance properties allow lookdowns to reflect the uniform degree and angle of polarization associated with high-noon conditions due to alignment of the principle axes and the sun, and reflect a more complex polarization pattern at asymmetrical light fields associated with lower solar elevations. Our results suggest that polaro-cryptic strategies vary by habitat, and require context-specific depolarization and angle alteration for effective concealment in the complex open ocean environment.