DNA barcoding reveals different cestode helminth species in northern European marine and freshwater ringed seals

Tommi Nyman; Elena Papadopoulou; Eeva Ylinen; Saskia Wutke; Craig T Michell; Ludmila Sromek; Tuula Sinisalo; Elena Andrievskaya; Vyacheslav Alexeev; Mervi Kunnasranta

doi:10.1016/j.ijppaw.2021.06.004

DNA barcoding reveals different cestode helminth species in northern European marine and freshwater ringed seals

Int J Parasitol Parasites Wildl. 2021 Jun 24:15:255-261. doi: 10.1016/j.ijppaw.2021.06.004. eCollection 2021 Aug.

Authors

Affiliations

¹ Department of Ecosystems in the Barents Region, Norwegian Institute of Bioeconomy Research, Svanvik, Norway.
² Department of Environmental and Biological Sciences, University of Eastern Finland, Joensuu, Finland.
³ Department of Marine Ecosystems Functioning, Institute of Oceanography, University of Gdansk, Gdynia, Poland.
⁴ Department of Biological and Environmental Sciences, University of Jyväskylä, Jyväskylä, Finland.
⁵ The Baltic Ringed Seal Foundation, St. Petersburg, Russia.
⁶ Natural Resources Institute Finland, Joensuu, Finland.

Abstract

Three subspecies of the ringed seal (Pusa hispida) are found in northeastern Europe: P. h. botnica in the Baltic Sea, P. h saimensis in Lake Saimaa in Finland, and P. h. ladogensis in Lake Ladoga in Russia. We investigated the poorly-known cestode helminth communities of these closely related but ecologically divergent subspecies using COI barcode data. Our results show that, while cestodes from the Baltic Sea represent Schistocephalus solidus, all worms from the two lakes are identified as Ligula intestinalis, a species that has previously not been reported from seals. The observed shift in cestode communities appears to be driven by differential availability of intermediate fish host species in marine vs. freshwater environments. Both observed cestode species normally infect fish-eating birds, so further work is required to elucidate the health and conservation implications of cestode infections in European ringed seals, whether L. intestinalis occurs also in marine ringed seals, and whether the species is able to reproduce in seal hosts. In addition, a deep barcode divergence found within S. solidus suggests the presence of cryptic diversity under this species name.

Keywords: COI barcoding; Cestoda; Freshwater seals; Ligula intestinalis; Pusa hispida; Schistocephalus solidus.