Eilertsen Mariann, Valen Ragnhild, Drivenes Øyvind, Ebbesson Lars O E, Helvik Jon Vidar
Department of Biological Sciences, University of Bergen, N- 5020 Bergen, Norway.
Department of Molecular Biology, University of Bergen, N- 5020 Bergen, Norway.
Dev Biol. 2018 Dec 15;444(2):129-138. doi: 10.1016/j.ydbio.2018.10.006. Epub 2018 Oct 19.
In nonmammalian vertebrates, photoreception takes place in the deep brain already early in development, but knowledge is lacking about the functions of these nonvisual photoreceptive systems. Prior to hatching, Atlantic halibut has a transient bilateral cluster of photoreceptive cells in the hindbrain. The cluster is imbedded in a neuronal network projecting to the narrow belt of hatching glands in the yolk sac. In halibut, hatching is inhibited in light and activated by transfer to darkness and c-fos analysis during hatching shows that the hindbrain cluster and hatching glands have neural activation. Unexpectedly, the hindbrain cluster expresses dual photopigments, vertebrate ancient opsin and melanopsin. Evolutionarily, these opsins are believed to belong to different classes of photopigments found in rhabdomeric and ciliary photoreceptors. The concept that an organism develops transient light sensitivity to target critical aspects of life history transitions as hatching provides a fascinating landscape to investigate the timing of other biological events.
在非哺乳动物脊椎动物中，光感受在发育早期就已在脑深部发生，但对于这些非视觉光感受系统的功能尚缺乏了解。在孵化前，大西洋庸鲽在后脑中有一群短暂存在的双侧光感受细胞。该细胞群嵌入一个神经网络，该网络投射至卵黄囊中狭窄的孵化腺带。在庸鲽中，光照会抑制孵化，而转移至黑暗环境则会激活孵化，并且孵化过程中的c-fos分析表明，后脑细胞群和孵化腺有神经激活。出乎意料的是，后脑细胞群表达两种光色素，即脊椎动物古老视蛋白和黑视蛋白。从进化角度来看，这些视蛋白被认为属于在微绒毛型和纤毛型光感受器中发现的不同类别的光色素。生物体在孵化时形成短暂的光敏感性以针对生命史转变的关键方面这一概念，为研究其他生物事件的时间安排提供了一个引人入胜的领域。
