The distribution and diversity of species in the genus Owenia (Polychaeta) in Norwegian waters

Abstract

In this study the diversity and distribution of Owenia species in Norwegian waters are discussed. Owenia fusiformis and the Owenia genus has gone through a turbulent history, with authors describing several new species, while other researchers have disagreed, resulting in many described species being synonymized with O. fusiformis. Norwegian waters are no exception, and the majority of samples in natural history collections are still referred to as Owenia fusiformis. In this study both morphological and molecular methods will be used to solve the issue regarding the true identity of Owenia in Norwegian waters. Along with morphological character two genes, COI and ITS1, was sequenced and analyzed. COI proved to be very difficult to extract and amplify successfully for one group of specimens, from which no successful sequences were obtained, while being relatively unproblematic in other groups, leading the question if the COI primers are accurate enough. ITS1 was unproblematic to amplify and sequence, but due to highly variable sequences, a lot of effort was needed to analyze the dataset. Morphological characters proved to exhibit high degrees of the variation, resulting in most of the defined characters being useless in differentiating between the species. Still, enough useful morphologic characters, the best one being the methyl blue staining pattern, were defined, making it possible to distinguish between different species occurring in Norwegian waters. This being congruent with the molecular results, led to the conclusion that at least two different species of Owenia is present in Norwegian waters, Owenia borealis Koh, Bhaud & Jirkov, 2003 and Owenia polaris Koh, Bhaud & Jirkov, with results also suggesting there might be more. Type specimens of Owenia assimilis (Sars, 1851) were also examined, concluding with this probably being identical to O. borealis, although the possibility of the type material being more than one species, leads to this being an open question, in need of more research before an answer can be given. Specimens from the O. fusiformis type locality were also examined, concluding with the presence of the true O. fusiformis in Norwegian waters being highly unlikely.