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Next article FreeAbout the CoverPDFPDF PLUSFull Text Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinked InRedditEmailQR Code SectionsMoreCoverSerpulid fan worms are sessile polychaetes that live in excreted tubes in the marine substrate. From their heads they project specialized feeding tentacles, called radioles, into the water column. They protect these exposed radioles with unusual photosensors, or eyes, located on the tentacles themselves. These eyes function as shadow-detecting alarms that identify looming threats and trigger a rapid withdrawal of the radioles into the worm’s fortified tube. Pictured on the cover is the most elaborate example of radiolar eyes: those found on the tentacles of the Christmas tree worm Spirobranchus corniculatus (Grube, 1862) from the Great Barrier Reef in Australia. These oddly-shaped compound eyes (orange-colored region) are composed of over 1000 individual optical elements, called ocelli.On pages 39–57 of this issue, Michael Bok, Megan Porter, Harry ten Hove, Richard Smith, and Dan-Eric Nilsson examine the broad diversity of radiolar eyes throughout the serpulid family, from single, scattered ocelli to the sophisticated compound eyes of S. corniculatus. They report on the phototransduction cascade transcripts expressed in the eyes of S. corniculatus, including opsins that belong to a poorly understood clade typically found in the brains of some invertebrate phyla. Furthermore, they describe and compare the fine structure of the ciliary photoreceptors found in the radiolar eyes of five species of serpulids. The authors consider the functional and evolutionary implications of these unique photoreceptors among the serpulid family and within the broader context of animal eye evolution.Credits: Photo, © Michael Bok, Lund University, Sweden. Cover design: Jeannie Harrell, University of Chicago Press. Next article DetailsFiguresReferencesCited by The Biological Bulletin Volume 233, Number 1August 2017New Insights from Genetic Data Sets on the Function and Evolution of Visual Systems Published in association with the Marine Biological Laboratory Article DOIhttps://doi.org/10.1086/696189 © 2017 by The University of Chicago. All rights reserved.PDF download Crossref reports no articles citing this article.