Section of Marine Biology, Department of Biology, University of Copenhagen, , Universitetsparken 4, Copenhagen Ø 2100, Denmark, Lund Vision Group, Department of Biology, Lund University, , Sölvegatan 35, Lund 22362, Sweden.
Proc Biol Sci. 2014 Jan 8;281(1777):20133011. doi: 10.1098/rspb.2013.3011. Print 2014 Feb 22.
Most known starfish species possess a compound eye at the tip of each arm, which, except for the lack of true optics, resembles an arthropod compound eye. Although these compound eyes have been known for about two centuries, no visually guided behaviour has ever been directly associated with their presence. There are indications that they are involved in negative phototaxis but this may also be governed by extraocular photoreceptors. Here, we show that the eyes of the coral-reef-associated starfish Linckia laevigata are slow and colour blind. The eyes are capable of true image formation although with low spatial resolution. Further, our behavioural experiments reveal that only specimens with intact eyes can navigate back to their reef habitat when displaced, demonstrating that this is a visually guided behaviour. This is, to our knowledge, the first report of a function of starfish compound eyes. We also show that the spectral sensitivity optimizes the contrast between the reef and the open ocean. Our results provide an example of an eye supporting only low-resolution vision, which is believed to be an essential stage in eye evolution, preceding the high-resolution vision required for detecting prey, predators and conspecifics.
大多数已知的海星物种在每条臂的末端都有一只复眼，除了缺乏真正的光学结构外，这些复眼类似于节肢动物的复眼。尽管这些复眼已经被人们了解了大约两个世纪，但它们的存在从未与任何直接的视觉引导行为联系起来。有迹象表明，它们参与了负趋光性，但这也可能受到眼外光感受器的控制。在这里，我们证明了与珊瑚礁相关的海星 Linckia laevigata 的眼睛反应缓慢且对颜色不敏感。这些眼睛能够进行真正的成像，尽管空间分辨率较低。此外，我们的行为实验表明，只有眼睛完好无损的标本才能在被转移后导航回到它们的珊瑚礁栖息地，这表明这是一种视觉引导行为。据我们所知，这是首次报道海星复眼具有功能。我们还表明，光谱灵敏度优化了珊瑚礁和开阔海洋之间的对比度。我们的研究结果提供了一个仅支持低分辨率视觉的眼睛的例子，这被认为是眼睛进化的一个重要阶段，先于检测猎物、捕食者和同种个体所需的高分辨率视觉。
