Ugolini Alberto, Hariyama Takahiko, Wilcockson David C, Mercatelli Luca
Dipartimento Di Biologia, Università Di Firenze, Via Romana 17-19, 50125, Florence, Italy.
Institute for NanoSuit Research, Preeminent Medical Photonics Education and Research Center, Hamamatsu University, School of Medicine, 1-20-1 Handayama, Higashi-Ku, Hamamatsu, 431-3192, Japan.
Zoological Lett. 2023 May 18;9(1):10. doi: 10.1186/s40851-023-00207-8.
It is well known that the celestial polarization is used as a compass cue by many species of insects and crustaceans. Although it has been shown that the sandhopper Talitrus saltator perceives polarized light and possesses an arrangement of the rhabdomeres that could allow e-vector interpretation and utilization, T. saltator does not use the e-vector of the skylight polarization as a compass cue when making excursions along the sea-land axis of sandy shores. We performed tests in confined conditions to clarify if skylight polarization is somehow involved in the zonal recovery of T. saltator. We observed the directional responses of sandhoppers in a transparent bowl under an artificial sky (an opaline Plexiglas dome). The bowl was covered by a blue gelatin filter with a grey filter (control condition) and a linear polarizing filter (experimental conditions) positioned under the blue one in such a way as to occupy half of the upper surface of the Plexiglas bowl so as to create a linear polarization gradient. Our experiments confirm that T. saltator perceives polarized light and highlight that this visual capability determines the perception, or perhaps the increase, of the radiance and/or spectral gradient and their use as compass cues in the zonal orientation. Moreover, our findings confirm that the radiance gradient is used as a chronometric compass orienting reference in the absence of other celestial orienting cues.
众所周知，天体偏振光被许多昆虫和甲壳类动物用作罗盘线索。尽管已经表明跳虫Talitrus saltator能够感知偏振光，并且具有一种视杆的排列方式，这种排列方式可能允许对电场矢量进行解读和利用，但当沿着沙滩的海陆轴进行短途移动时，Talitrus saltator并不将天空光偏振的电场矢量用作罗盘线索。我们在受限条件下进行了测试，以弄清楚天空光偏振是否以某种方式参与了Talitrus saltator的区域恢复。我们在人造天空（一个乳白有机玻璃穹顶）下的透明碗中观察了跳虫的定向反应。碗上覆盖着一个蓝色明胶滤光片，在蓝色滤光片下方放置了一个灰色滤光片（对照条件）和一个线性偏振滤光片（实验条件），其放置方式是占据有机玻璃碗上表面的一半，以便形成一个线性偏振梯度。我们的实验证实Talitrus saltator能够感知偏振光，并强调这种视觉能力决定了对辐射度和/或光谱梯度的感知，或者可能是增强，以及它们在区域定向中作为罗盘线索的使用。此外，我们的研究结果证实，在没有其他天体定向线索的情况下，辐射度梯度被用作计时罗盘定向参考。
