University of Cambridge > > Zoology Departmental Seminar Series > Seeing the world in a new light: Polychaete worms wriggle winding evolutionary paths to vision

Seeing the world in a new light: Polychaete worms wriggle winding evolutionary paths to vision

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Vision is a powerful sense, and evolution has invented a multitude of fascinating eye designs that allow animals to see their world. Some of the strangest examples of eyes can be found in polychaete worms, and they are a dynamic group in which to study the forces that shape the optical, neurological, and behavioral components of visual systems. Here, I will present two stories about the bizarre eyes of polychaetes: The bulbous, camera-type eyes of enigmatic pelagic alciopids, and the multitudinous, distributed compound eyes of sedentary fanworms.

Alciopids have dramatically enlarged their eyes, possibly affording them with high-resolution vision, a feat only confirmed in chordates, arthropods, and cephalopods. However, they have been difficult to collect reliably, intact, and in large numbers. Recently we identified an ideal field site for collecting these worms, and have been able to probe the acuity of their vision using optical, anatomical, and electrophysiological techniques. We confirm that they likely have high-resolution vision and propose exciting possibilities for the function of their eyes.

Fanworms are sedentary aquatic polychaetes that reside within protective tubes anchored to the substrate. They extend a feathery crown of radiolar tentacles into the water column from their heads for feeding. Fanworms rely on sensory structures on the radioles to detect threats and trigger a rapid retraction into their tubes. In many species these structures include dozens of unusual compound eyes, which can be found in a great diversity of arrangements and sophistications. We used phylogenetics, electron microscopy and micro-CT to trace the functional evolution of these eyes and discovered a complex tapestry of eye gain, loss, and elaboration. Furthermore, we used behavioral experiments to test the visual capabilities of species with variable eye designs, and found that some fan worms are likely in a unique evolutionary trajectory where something resembling image-forming vision may be emerging from their alarm response system. Taken together, our findings highlight the astounding evolutionary creativity of sensory systems that can be leveraged to solve crucial ecological challenges.

This talk is part of the Zoology Departmental Seminar Series series.

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