First time DNA barcoding of the common shipworm Teredo navalis Linnaeus 1758 (Mollusca: Bivalvia: Teredinidae): Molecular-taxonomic investigation and identification of a widespread wood-borer

•Three new COI primers for barcoding of Teredinidae were developed.•No differentiation between European and American Teredo navalis was found.•Only one wood-boring bivalve was detected in the proper Baltic Sea.•No sibling species of Teredo navalis was identified in the studied sampling areas.•Bivalve teredinid Teredo navalis seems to expand its recent population in Europe.

The common shipworm Teredo navalis is one of the most widespread marine wood-boring bivalves of the world and probably one of the most wood destructive and cost-incurring marine invertebrates. First reports on T. navalis for Europe date back to 1731 for the North Sea (The Netherlands) and to 1835 for the Baltic Sea (Germany). It is still unclear, however, where this species originates from. Therefore, T. navalis is considered cryptogenic for European waters, including the Baltic Sea.In this study, 181 specimens of Teredinidae from six different sampling areas all over Europe and North America were molecular-taxonomically investigated using several molecular markers, two nuclear (18S/28S) as well as one mitochondrial marker (cytochrome c oxidase subunit I, hereafter COI). For the COI gene amplification, a new specific primer pair (Ter fw II/Ter rev I) for T. navalis was developed, which allowed sequencing of a 675 bp COI gene fragment for the first time. For amplifying the COI gene fragment of other examined teredinids than T. navalis, a third primer (Ter fw III) was designed. These three new primers are valuable tools to identify teredinid species with the DNA barcoding approach.Classification of T. navalis into the system of wood-boring bivalves using a combined 18S/28S dataset showed no differentiation between specimens from Europe and the North American East Coast. The results of the COI dataset analyses showed high haplotype diversity in combination with a low nucleotide diversity and a star-shaped network with a predominant haplotype occurring in all investigated regions. Moreover, no indications have been found on a sibling species in the Baltic Sea. The data indicate a recent population expansion for the examined sampling sites whereas the origin of the assumed worldwide distributed species T. navalis remains open.