School of Life Sciences, Arizona State University, Tempe, AZ 85287 USA
Department of Neuroscience, University of Arizona, 611 Gould-Simpson, Tucson, AZ 85721, USA.
J Exp Biol. 2018 May 22;221(Pt 10):jeb165878. doi: 10.1242/jeb.165878.
Light is a primary environmental factor used by aquatic invertebrates for depth selection behavior. Many branchiopod crustaceans live in ephemeral aquatic habitats. All branchiopod crustaceans studied to date express four or more visual opsins in their compound eyes. We asked whether two branchiopods, and , use multiple spectral channels to regulate their position in the water column. At the lowest intensities that elicited photonegative behavior, both species had broad spectral bandwidths, suggesting they use multiple spectral photoreceptor classes. Male were more likely to maintain a vertical position 8.0-12.0 cm below the surface than females, independently of whether females were present. Male photopositive behavior at low intensity was restricted to a narrow bandwidth centered at 532 nm, suggesting a single photoreceptor class is used to maintain position above females. We compared ephemeral pools from two regions in Arizona and found that diffuse light attenuation coefficients were two orders of magnitude greater than the most heavily attenuating coastal waters. At less than 1 m of depth, pools were often dimmer than terrestrial habitats under starlight. Soil particle size distribution in each region affected spectral light environments, and behavioral responses of field-caught shrimp were adapted to the spectral properties of their region. The results suggest that branchiopods predominantly use luminance vision summed from multiple spectral photoreceptor classes for depth selection in dim, spectrally variable environments. The neuroanatomical basis for summation is described in a companion paper.
光是水生无脊椎动物用于深度选择行为的主要环境因素。许多枝角类甲壳动物生活在短暂的水生栖息地。迄今为止，所有研究过的枝角类甲壳动物在其复眼中都表达了四种或更多种视觉视蛋白。我们想知道两种枝角类动物， 和 ，是否使用多个光谱通道来调节它们在水柱中的位置。在引起光负性行为的最低强度下，这两个物种的光谱带宽都很宽，这表明它们使用了多种光谱光感受器类型。与雌性无关，雄性 比雌性更有可能保持在离水面 8.0-12.0cm 的垂直位置。雄性在低强度下的光正性行为仅限于一个以 532nm 为中心的窄带宽，表明只使用一种光感受器类型来维持在雌性上方的位置。我们比较了来自亚利桑那州两个地区的短暂性池塘，发现漫射光衰减系数比最强烈衰减的沿海水域高出两个数量级。在不到 1m 的深度，池塘在星光下通常比陆地栖息地暗。每个地区的土壤颗粒大小分布都会影响光谱光环境，而野外捕获的虾的行为反应则适应了它们所在地区的光谱特性。结果表明，枝角类动物主要使用来自多个光谱光感受器类型的亮度视觉来在暗淡、光谱多变的环境中进行深度选择。用于求和的神经解剖学基础在一篇配套论文中进行了描述。
