Charpentier Corie L, Cohen Jonathan H
School of Marine Science and Policy, College of Earth, Ocean and Environment, University of Delaware, 700 Pilottown Road, Lewes, DE 19958, USA
School of Marine Science and Policy, College of Earth, Ocean and Environment, University of Delaware, 700 Pilottown Road, Lewes, DE 19958, USA.
J Exp Biol. 2015 Nov;218(Pt 21):3381-90. doi: 10.1242/jeb.125229.
Several predator avoidance strategies in zooplankton rely on the use of light to control vertical position in the water column. Although light is the primary cue for such photobehavior, predator chemical cues or kairomones increase swimming responses to light. We currently lack a mechanistic understanding for how zooplankton integrate visual and chemical cues to mediate phenotypic plasticity in defensive photobehavior. In marine systems, kairomones are thought to be amino sugar degradation products of fish body mucus. Here, we demonstrate that increasing concentrations of fish kairomones heightened sensitivity of light-mediated swimming behavior for two larval crab species (Rhithropanopeus harrisii and Hemigrapsus sanguineus). Consistent with these behavioral results, we report increased visual sensitivity at the retinal level in larval crab eyes directly following acute (1-3 h) kairomone exposure, as evidenced electrophysiologically from V-log I curves and morphologically from wider, shorter rhabdoms. The observed increases in visual sensitivity do not correspond with a decline in temporal resolution, because latency in electrophysiological responses actually increased after kairomone exposure. Collectively, these data suggest that phenotypic plasticity in larval crab photobehavior is achieved, at least in part, through rapid changes in photoreceptor structure and function.
浮游动物的几种避敌策略依赖于利用光线来控制其在水柱中的垂直位置。尽管光线是这种光行为的主要线索，但捕食者的化学线索或信息素会增强对光的游泳反应。目前，我们对于浮游动物如何整合视觉和化学线索以介导防御性光行为中的表型可塑性缺乏机制上的理解。在海洋系统中，信息素被认为是鱼类体表黏液的氨基糖降解产物。在此，我们证明，对于两种幼体蟹类（哈氏方蟹和红螯相手蟹），鱼类信息素浓度的增加提高了光介导游泳行为的敏感性。与这些行为结果一致，我们报告称，在急性（1 - 3小时）信息素暴露后，幼体蟹眼视网膜水平的视觉敏感性增加，这在电生理学上通过V - log I曲线得以证明，在形态学上则表现为视杆更宽、更短。观察到的视觉敏感性增加与时间分辨率的下降并不对应，因为在信息素暴露后，电生理反应的潜伏期实际上增加了。总体而言，这些数据表明，幼体蟹光行为的表型可塑性至少部分是通过光感受器结构和功能的快速变化实现的。
