Environmental Optics Laboratory, Department of Biological Physics, Physical Institute, Eötvös University, Budapest, Hungary.
PLoS One. 2012;7(8):e41138. doi: 10.1371/journal.pone.0041138. Epub 2012 Aug 2.
During blood-sucking, female members of the family Tabanidae transmit pathogens of serious diseases and annoy their host animals so strongly that they cannot graze, thus the health of the hosts is drastically reduced. Consequently, a tabanid-resistant coat with appropriate brightness, colour and pattern is advantageous for the host. Spotty coats are widespread among mammals, especially in cattle (Bos primigenius). In field experiments we studied the influence of the size and number of spots on the attractiveness of test surfaces to tabanids that are attracted to linearly polarized light. We measured the reflection-polarization characteristics of living cattle, spotty cattle coats and the used test surfaces. We show here that the smaller and the more numerous the spots, the less attractive the target (host) is to tabanids. We demonstrate that the attractiveness of spotty patterns to tabanids is also reduced if the target exhibits spottiness only in the angle of polarization pattern, while being homogeneous grey with a constant high degree of polarization. Tabanid flies respond strongly to linearly polarized light, and we show that bright and dark parts of cattle coats reflect light with different degrees and angles of polarization that in combination with dark spots on a bright coat surface disrupt the attractiveness to tabanids. This could be one of the possible evolutionary benefits that explains why spotty coat patterns are so widespread in mammals, especially in ungulates, many species of which are tabanid hosts.
在吸血过程中，虻科的雌性成员会传播严重疾病的病原体，并强烈骚扰它们的宿主动物，使它们无法放牧，从而大大降低宿主的健康水平。因此，对于宿主来说，具有适当亮度、颜色和图案的抗虻外套是有利的。斑点图案在哺乳动物中很常见，尤其是在牛（Bos primigenius）中。在野外实验中，我们研究了斑点的大小和数量对被线性偏振光吸引的虻类对测试表面吸引力的影响。我们测量了活体牛、有斑点的牛外套和使用的测试表面的反射偏振特性。我们在这里表明，斑点越小且数量越多，目标（宿主）对虻类的吸引力就越小。我们证明，如果目标仅在偏振图案的角度上显示出斑点，而具有恒定高偏振度的均匀灰色，则斑点图案对虻类的吸引力也会降低。虻类苍蝇对线性偏振光反应强烈，我们表明，牛外套的亮暗部分反射光的程度和角度不同，结合亮面上的暗点会破坏对虻类的吸引力。这可能是解释为什么斑点图案在哺乳动物中如此广泛存在的一个可能的进化优势，尤其是在许多种类的虻类宿主的有蹄类动物中。
