Evolution of Eyes in Annelids

Project Title: Evolution of photoreceptor cells and eyes in Annelida

Funding Source: DFG (in part)

Principle Investigator: Günter Purschke with Detlev Arendt, EMBL Heidelberg; Harald Hausen, SARS Institute Bergen; Patrick Beckers, University of Bonn; Stepan Vodopyanov, Moscow State University; et al.

Investigations on evolution, systematics, phylogeny and functional morphology are in the focus of interest. Currently these investigations are carried out on annelids, the segmented worms, and those taxa which are presumed to be closely related to them. Special emphasis is laid to the phylogenetic relationships within and validity of Lophotrochozoa.

After detecting Pax6 as master control gene for eye development and ciliary and rhabdomeric photoreceptor cells (PRC) as sister cell types in Metazoa, the evolutionary history of eyes within Metazoa seemed to be resolved. However, annelids possess two different generations of cerebral eyes: larval eyes and adult eyes. Clarifying the evolutionary history and their fate in the diverse groups is in center of this project. Current investigations are related to elucidate the structure of the eyes in the last common ancestor (LCA) of Annelida and the time point where the typical adult eyes have been evolved and what their fate was during diversification of Annelida. So likelihood increases that two pairs of adult eyes where present in the LCA of a clade comprising Amphinomida and Pleistoannelida, and their subsequent reduction in certain but not all lines of Sedentaria within the latter. Moreover, several taxa are provided with highly specialized and divergent eyes occurring elsewhere on the body such as the posterior (pygidial) eyes of Sabellidae or eyes present on the median organ in the sand corals, Sabellariidae.

Movie: Sabellaria alveolata.

The movie shows the escape behavior of sand castle worms (Sabellaria alveolata) induced by shadow as occurring when predators approach. Video by Larisse Faroni-Perez, Brazil.