Ogawa Yuri, Ribi Willi, Zeil Jochen, Hemmi Jan M
School of Biological Sciences and UWA Oceans Institute (M092), The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia
Department of Biological Sciences, Macquarie University, Sydney, NSW 2109, Australia.
J Exp Biol. 2017 May 1;220(Pt 9):1701-1708. doi: 10.1242/jeb.156109. Epub 2017 Feb 17.
In addition to compound eyes, honeybees () possess three single-lens eyes called ocelli located on the top of the head. Ocelli are involved in head-attitude control and in some insects have been shown to provide celestial compass information. Anatomical and early electrophysiological studies have suggested that UV and blue-green photoreceptors in ocelli are polarization sensitive. However, their retinal distribution and receptor characteristics have not been documented. Here, we used intracellular electrophysiology to determine the relationship between the spectral and polarization sensitivity of the photoreceptors and their position within the visual field of the ocelli. We first determined a photoreceptor's spectral response through a series of monochromatic flashes (340-600 nm). We found UV and green receptors, with peak sensitivities at 360 and 500 nm, respectively. We subsequently measured polarization sensitivity at the photoreceptor's peak sensitivity wavelength by rotating a polarizer with monochromatic flashes. Polarization sensitivity (PS) values were significantly higher in UV receptors (3.8±1.5, =61) than in green receptors (2.1±0.6, =60). Interestingly, most receptors with receptive fields below 35 deg elevation were sensitive to vertically polarized light while the receptors with visual fields above 35 deg were sensitive to a wide range of polarization angles. These results agree well with anatomical measurements showing differences in rhabdom orientations between dorsal and ventral retinae. We discuss the functional significance of the distribution of polarization sensitivities across the visual field of ocelli by highlighting the information the ocelli are able to extract from the bee's visual environment.
除复眼外，蜜蜂在头顶还拥有三只称为单眼的单透镜眼。单眼参与头部姿态控制，并且在一些昆虫中已被证明能提供天体罗盘信息。解剖学和早期电生理学研究表明，单眼中的紫外光和蓝绿色光感受器对偏振敏感。然而，它们在视网膜上的分布和感受器特征尚未得到记录。在这里，我们使用细胞内电生理学来确定光感受器的光谱和偏振敏感性与其在单眼光视野内位置之间的关系。我们首先通过一系列单色闪光（340 - 600纳米）确定光感受器的光谱响应。我们发现了紫外光和绿光感受器，其峰值敏感性分别在360纳米和500纳米处。随后，我们通过用单色闪光旋转偏振器，在光感受器的峰值敏感性波长处测量偏振敏感性。紫外光感受器的偏振敏感性（PS）值（3.8±1.5，n = 61）显著高于绿光感受器（2.1±0.6，n = 60）。有趣的是，大多数感受野低于仰角35度的感受器对垂直偏振光敏感，而视野高于35度的感受器对广泛的偏振角度敏感。这些结果与解剖学测量结果非常吻合，后者显示了背侧和腹侧视网膜之间视杆方向的差异。我们通过强调单眼能够从蜜蜂视觉环境中提取的信息，讨论了单眼光视野内偏振敏感性分布的功能意义。
