Here, There and Everywhere: The Radiolar Eyes of Fan Worms (Annelida, Sabellidae)
Here, There and Everywhere: The Radiolar Eyes of Fan Worms (Annelida, Sabellidae)
复制标题
DOI：
10.1093/icb/icw089
复制
发表时间：
2016-11-01
影响因子：
2.6
通讯作者：
Nilsson, Dan-Eric
中科院分区：
文献类型：
--
作者：
Bok, Michael J.;Capa, Maria;Nilsson, Dan-Eric
扇虫（环节虫：Sabellidae）拥有自然界中最奇怪的眼睛。它们的同名扇子由两组放射状触手组成，这些触手从头部向上伸出蠕虫的保护管进入水柱。这些放射线主要用于呼吸和进食，也经常参与光接收。它们的眼睛呈现出令人惊讶的多样性，其复杂程度各不相同，从分散的单眼到具有多达数百个面的复眼。这些光感受器可能代表了一种相对较新的进化发展，以应对固着的、居住在管中的生活方式，而主脑眼（不幸的是，大部分时间都位于管内）只不过是微小的色素杯，几乎没有视觉潜力。另一方面，放射状的眼睛似乎起到视觉防盗警报的作用，用于检测迫近的捕食者，并引起蠕虫的惊吓反应，使其迅速撤退到其强化管内。尽管有时类似于节肢动物的复眼，但放射光感受器具有许多典型的脊椎动物样生理特征。考虑到扇虫放射光感受器的不寻常且显然是最近进化的性质，这些动物是研究新颖视觉系统的出现、基本视觉引导行为的发展以及分布式感觉系统功能的绝佳案例。在这里，我们回顾了 100 多年来在进化和功能背景下对萨贝利德放射光感受器和眼睛的解剖多样性的研究。我们提供了有关几种扇虫的放射眼结构的新信息，并尝试将各种眼睛类型和眼状结构组织成有意义的层次结构。我们讨论了放射眼的发育、进化和功能意义，并重点介绍了破译其独特性质的未来感兴趣的领域。
Fan worms (Annelida: Sabellidae) possess some of the strangest eyes in nature. Their eponymous fans are composed of two sets of radiolar tentacles that project from the head up out of the worm's protective tube into the water column. Primarily used for respiration and feeding, these radioles are also often involved in photoreception. They display a surprising diversity of eyes of varying levels of sophistication, ranging from scattered single ocelli to compound eyes with up to hundreds of facets. These photoreceptors could represent a relatively recent evolutionary development to cope with a sessile, tube-dwelling lifestyle, and the primary cerebral eyes (haplessly positioned within the tube most of the time) amount to little more than minute pigment cups with scant visual potential. The radiolar eyes on the other hand, appear to function as visual burglar alarms for detecting looming predators and eliciting a startle response for the worm to rapidly retreat within its fortified tube. Despite sometimes resembling arthropod compound eyes, the radiolar photoreceptors have many canonically vertebrate-like physiological characteristics. Considering the unusual and apparently recently evolved nature of the fan worm radiolar photoreceptors, these animals are an excellent case for examining the emergence of novel visual systems, the development of rudimentary visually guided behaviors, and the function of distributed sensory systems. Here, we review over 100 years of investigations into the anatomical diversity of sabellid radiolar photoreceptors and eyes in an evolutionary and functional context. We provide new information on radiolar eye structure in several species of fan worms, and we attempt to organize the various eye types and ocellar structures into meaningful hierarchies. We discuss the developmental, evolutionary, and functional significance of the radiolar eyes and highlight areas of future interest in deciphering their unique nature.