The proposed 2-year project conducted at the University Museum of Bergen (Norway) will address the questions on the evolution of the deep-sea fauna. It will focus on the group of predominantly deep-sea polychaete worms from the subfamily Hyalinoeciinae with worldwide distribution, remarkable diversity at great depths, and possible progenetic origin. The project will study the morphology, taxonomy and phylogeny of hyalinoeciin polychaetes and will evaluate the role of progenesis within Hyalinoeciinae in their successful colonization of the deep sea. The project will be based on the unique and extensive collection of the deep-sea hyalinoeciins appropriate for the DNA analysis and will also utilize materials from a number of European research institutions. It will combine the methods of traditional taxonomy with the state of the art molecular techniques. This study aims to: (1) assess the morphological and genetic variation within Hyalinoeciinae; (2) assess the phylogenetic position of Hyalinoeciinae species with suggested progenetic origin; (3) trace the evolution of characters within Hyalinoeciinae; (4) develop a hypothesis on the possible pathways of the deep-sea invasion by hyalinoeciins. The expected results will: provide taxonomical revision of hyalinoeciins; advance understanding of genetic and morphological variation in polychaetes from various depth zones; advance knowledge in polychaete phylogeny; and contribute to understanding of the role of progenesis in the deep-sea fauna formation and evolution. The project will be among the first studies of evolutionary processes within deep-sea polychaetes, one of the dominant groups of organisms inhabiting soft-bottom deep-sea communities, and will significantly strengthen European excellence and competitiveness in this area of marine studies. The project with facilitate the establishment of mutual collaborative links between the deep-sea scientists in Norway, Germany, the UK and Russian research community.