Nuckley D J, Jinks R N, Battelle B A, Herzog E D, Kass L, Renninger G H, Chamberlain S C
Department of Bioengineering and Neuroscience, Syracuse University, New York 13244-1240, USA.
Biol Bull. 1996 Feb;190(1):98-110. doi: 10.2307/1542679.
A new species of shrimp (Rimicaris sp.) was recently collected from the Snake Pit hydrothermal vent field on the Mid-Atlantic Ridge. Until the discovery in 1989 that the deep-sea, hydrothermal vent species, Rimicaris exoculata, possessed a hypertrophied dorsal eye, everyone believed that animals recovered from vent environments were blind. Like R. exoculata, Rimicaris sp., a small orange bresiliid shrimp, has an enlarged dorsal eye specialized for detecting light in a very dim environment instead of the expected compound eye. The individual lenses characteristic of a compound eye adapted for imaging have been replaced in Rimicaris sp. by a smooth cornea underlain by a massive array of photosensitive membrane. The number of ommatidia in this species is about the same as in shrimp species that live at the surface; however, the photoreceptors are larger in the deep-sea species and the shape of the photoreceptors is markedly different. The light-sensitive region of the photoreceptor is much larger than those of other shrimp and the rest of the receptor is much smaller than normal. All screening pigment has moved out of the path of incident light to a position below the retina, and the reflecting pigment cells have adapted to form a bright white diffusing screen between and behind the photoreceptors. The ultrastructure of the microvillar array comprising the rhabdom is typical for decapod crustaceans; however, there is a much greater volume density of rhabdom (80% to 85%) than normal. There is no ultrastructural evidence for cyclic rhabdom shedding or renewal. Rimicaris sp. has apparently adapted its visual system to detect the very dim light emitted from the throats of the black smoker chimneys around which it lives.
最近，一种新的虾类物种（Rimicaris sp.）在中大西洋海岭的蛇坑热液喷口区域被采集到。直到1989年发现深海热液喷口物种Rimicaris exoculata拥有一个肥大的背眼之前，每个人都认为从喷口环境中采集到的动物是失明的。与R. exoculata一样，Rimicaris sp.是一种小型橙色布里西里德虾，它拥有一个扩大的背眼，专门用于在非常昏暗的环境中检测光线，而不是预期的复眼。适合成像的复眼中特有的单个晶状体，在Rimicaris sp.中已被一层光滑的角膜所取代，角膜下方是大量的光敏膜。该物种的小眼数量与生活在水面的虾类物种大致相同；然而，深海物种的光感受器更大，且光感受器的形状明显不同。光感受器的光敏区域比其他虾类的要大得多，而感受器的其余部分则比正常情况小得多。所有的屏蔽色素都已移出入射光的路径，移到了视网膜下方的一个位置，反射色素细胞已适应形成一个明亮的白色漫射屏，位于光感受器之间和后面。构成视杆的微绒毛阵列的超微结构对于十足目甲壳类动物来说是典型的；然而，视杆的体积密度比正常情况要大得多（80%至85%）。没有超微结构证据表明视杆存在周期性脱落或更新。Rimicaris sp.显然已经使其视觉系统适应了检测其周围黑烟囱喉部发出的非常昏暗的光线。
