First record and spread of the long-wristed hermit crab Pagurus longicarpus Say, 1817 in the North Frisian Wadden Sea (Germany).

The long-wristed hermit crab Pagurus longicarpus is native to the East Coast of North America from the Gulf of Mexico to the Gulf of St. Lawrence. Here we present the first record of this species in the German Wadden Sea. Sixty-one individuals of P. longicarpus were found during a regular beam trawl survey at nine stations in the Meldorf Bight in late August 2020. The identity of the new species was confirmed by DNA barcoding of mitochondrial subunit I of cytochrome c oxydase (COI). The northward spread up to Hallig Hooge was documented in 2021, with a total of 122 P. longicarpus found at 12 stations. Pagurus longicarpus was found in 2.5 m to 18.0 m depth at salinities of 24.89 to 30.43 PSU and temperatures ranging from 16.46 °C to 22.22 °C. We compared these parameters with the environmental conditions in its native range by using data from the Global Biodiversity Information Facility (GBIF) and the GIS database MARSPEC. The results revealed that environmental conditions in the North Frisian Wadden Sea closely fits those in the native range of P. longicarpus. Different size classes and sexes were identified, including ovigerous females, indicating a reproducing population in the North Frisian Wadden Sea. The species was most likely introduced via ballast water transport and seems to be already well established. [ABSTRACT FROM AUTHOR]