Looking with gills: The evolution and function of distributed visual systems in fan worms with a view to future resilient sensor arrays

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We are often fascinated to ponder how other animals see the world. Since most creatures have two primary eyes positioned prominently on the head, we are generally able to imagine some derivation or elaboration of our own view. However, there are some cases in which the visual system departs so wildly from ours that it is difficult to conceive how such a system would function, let alone provide the animal with useful information about the world. Marine fan worms possess arguably the most bizarre visual system in nature. These worms spend their lives within tubes on the sea floor, and project their eponymous fans, composed of numerous tentacles called radioles, up into the water column. These radioles are responsible for filter feeding, respiration, and amazingly - vision. In many species, the radioles are covered with variable arrangements of eyes; sometimes scattered in the hundreds on all of the radioles, other times consolidated into a pair of large compound eyes on the tips of two radioles, and in almost any arrangement in-between. These eyes likely function as a sort of optical burglar alarm, detecting the movement of looming threats and stimulating a rapid withdrawal into the fortified tube. My research has suggested that these radiolar eyes represent a completely novel evolutionary development, using light-sensing genes and neural pathways unlike those in the eyes of any other animal. These features make fan worms a spectacular study system to explore the origins of vision and the development of complexity and organization in distributed visual sensory systems. I propose to investigate the evolution and function of radiolar eyes in fan worms using molecular, neurobiological, and computational approaches. Next-generation sequencing techniques will be used to identify the genes involved in light detection and phototransduction, as well as developmental cues that give rise to the variable arrangements of eyes observed in different species of fan worms. I will also trace neuronal projections from the eyes to the brain in order to understand how information from a seemingly-chaotic, distributed array of eyes or ocelli is integrated and interpreted in order to stimulate a reliable startle response. Ultimately, I will draw upon these investigations in order to produce a synthetic model for simple, redundant, distributed optical sensory arrays that will have implications to biomimetic robotics.