Kriska György, Bernáth Balázs, Farkas Róbert, Horváth Gábor
Group for Methodology in Biology Teaching, Biological Institute, Eötvös University, Budapest, Hungary.
J Insect Physiol. 2009 Dec;55(12):1167-73. doi: 10.1016/j.jinsphys.2009.08.013. Epub 2009 Sep 10.
With few exceptions insects whose larvae develop in freshwater possess positive polarotaxis, i.e., are attracted to sources of horizontally polarized light, because they detect water by means of the horizontal polarization of light reflected from the water surface. These insects can be deceived by artificial surfaces (e.g. oil lakes, asphalt roads, black plastic sheets, dark-coloured cars, black gravestones, dark glass surfaces, solar panels) reflecting highly and horizontally polarized light. Apart from the surface characteristics, the extent of such a 'polarized light pollution' depends on the illumination conditions, direction of view, and the threshold p* of polarization sensitivity of a given aquatic insect species. p* means the minimum degree of linear polarization p of reflected light that can elicit positive polarotaxis from a given insect species. Earlier there were no quantitative data on p* in aquatic insects. The aim of this work is to provide such data. Using imaging polarimetry in the red, green and blue parts of the spectrum, in multiple-choice field experiments we measured the threshold p* of ventral polarization sensitivity in mayflies, dragonflies and tabanid flies, the positive polarotaxis of which has been shown earlier. In the blue (450nm) spectral range, for example, we obtained the following thresholds: dragonflies: Enallagma cyathigerum (0%<p*< or =17%), Ischnura elegans (17%< or =p*< or =24%). Mayflies: Baetis rhodani (32%< or =p*< or =55%), Ephemera danica, Epeorus silvicola, Rhithrogena semicolorata (55%< or =p*< or =92%). Tabanids: Tabanus bovinus, Tabanus tergestinus (32%< or =p*< or =55%), Tabanus maculicornis (55%< or =p*< or =92%).
除少数例外情况外，幼虫在淡水中发育的昆虫具有正向偏振趋光性，即被水平偏振光的光源所吸引，因为它们通过水面反射光的水平偏振来探测水。这些昆虫可能会被反射高偏振度水平偏振光的人造表面（如油湖、柏油路、黑色塑料布、深色汽车、黑色墓碑、深色玻璃表面、太阳能板）所欺骗。除了表面特征外，这种“偏振光污染”的程度还取决于光照条件、观察方向以及特定水生昆虫物种的偏振敏感度阈值p*。p表示能引发特定昆虫物种正向偏振趋光性的反射光的最小线性偏振度p。此前，关于水生昆虫p的定量数据并不存在。这项工作的目的就是提供此类数据。我们利用光谱中红、绿、蓝部分的成像偏振测量法，在多项选择野外实验中测量了蜉蝣、蜻蜓和虻的腹侧偏振敏感度阈值p*，此前已证明它们具有正向偏振趋光性。例如，在蓝色（450纳米）光谱范围内，我们得到了以下阈值：蜻蜓：蓝纹蟌（0%＜p*≤17%），美丽色蟌（17%≤p*≤24%）。蜉蝣：红圆尾蜉（32%≤p*≤55%），大蜉蝣、林栖蜉蝣、半色纹石蛾（55%≤p*≤92%）。虻：牛虻、的里雅斯特牛虻（32%≤p*≤55%），黄斑虻（55%≤p*≤92%）。
