(17) Ctenodrilus serratus (Schmidt, 1857)

Status in U.K. – cryptogenic.

There are two records of this species from the monitoring programme, from Kirkwall Marina in 2015 and from a scrape sample from Stromness Marina in 2016.

Ctenodrilus serratus has a worldwide distribution and is frequently found in aquaria (Fauvel 1927). It was genetically demonstrated to be truly amphi-Atlantic in distribution by Westheide et al. (2003), who concluded that the distribution must have been through dispersal and considered anthropogenic dispersal among the possibilities. It has been reported from the Plymouth area (Marine Biological Association 1957) and listed from the English Channel by Dauvin et al. (2003). It is found primarily in the vicinity of port facilities (unpublished data) and it is here considered to be cryptogenic in the U.K. The records presented here from 2015 and 2016 are the first from Orkney.