使海洋浮游植物群落依光照條件在海水表層及深層之間轉(zhuǎn)移的微小無脊椎動物幼蟲，可通過雙細胞眼點來探測光強度,，與達爾文所假設的作為哺乳動物眼睛進化起源的“原始眼睛”（protoeyes）相似,。
科學家對來自眼點的傳感信息被翻譯成運動的機制并不是很了解。Jékely等人研究了海洋蠕蟲巖蟲（Platynereis dumerilii）的幼蟲,，他們發(fā)現(xiàn),，眼點受到的光照，導致相鄰纖毛通過膽堿能信號作用產(chǎn)生的節(jié)拍發(fā)生一個變化,。計算機模型證實了趨光性所受到的這些局部效應的意義,，并且預測，如果該生物采取一個螺旋形游動模式的話,，其導航精確度將會提高,。光傳感與纖毛運動器以這種方式所進行的直接耦合，有可能是“原始眼睛”的一個功能,，是動物眼睛演化過程中的一個重要里程碑,。（生物谷Bioon.com）
生物谷推薦原始出處：
Nature 456, 395-399 (20 November 2008) | doi:10.1038/nature07590
Mechanism of phototaxis in marine zooplankton
Gáspár Jékely1,4, Julien Colombelli2, Harald Hausen3, Keren Guy1, Ernst Stelzer2, Fran?ois Nédélec2 & Detlev Arendt1
1 Developmental Biology Unit,
2 Cell Biology & Biophysics Unit, European Molecular Biology Laboratory, Heidelberg 69117, Germany
3 Institut für Biologie, Systematik und Evolution der Tiere, Freie Universit?t Berlin, Berlin 14195, Germany
4 Present address: Max Planck Institute for Developmental Biology, Tübingen 72076, Germany.
The simplest animal eyes are eyespots composed of two cells only: a photoreceptor and a shading pigment cell. They resemble Darwin's 'proto-eyes', considered to be the first eyes to appear in animal evolution1, 2, 3, 4. Eyespots cannot form images but enable the animal to sense the direction of light. They are characteristic for the zooplankton larvae of marine invertebrates and are thought to mediate larval swimming towards the light. Phototaxis of invertebrate larvae contributes to the vertical migration of marine plankton5, which is thought to represent the biggest biomass transport on Earth6, 7. Yet, despite its ecological and evolutionary importance, the mechanism by which eyespots regulate phototaxis is poorly understood. Here we show how simple eyespots in marine zooplankton mediate phototactic swimming, using the marine annelid Platynereis dumerilii as a model8. We find that the selective illumination of one eyespot changes the beating of adjacent cilia by direct cholinergic innervation resulting in locally reduced water flow. Computer simulations of larval swimming show that these local effects are sufficient to direct the helical swimming trajectories towards the light. The computer model also shows that axial rotation of the larval body is essential for phototaxis and that helical swimming increases the precision of navigation. These results provide, to our knowledge, the first mechanistic understanding of phototaxis in a marine zooplankton larva and show how simple eyespots regulate it. We propose that the underlying direct coupling of light sensing and ciliary locomotor control was a principal feature of the proto-eye and an important landmark in the evolution of animal eyes.
