Nematode Parasites in Baltic Sea Mammals, Grey Seal ( Halichoerus grypus (Fabricius, 1791)) and Harbour Porpoise ( Phocoena phocoena (L.)), from the German Coast

Abstract

Purpose

Endoparasitic nematodes of six harbour porpoises Phocoena phocoena and four grey seals Halichoerus grypus, stranded at the eastern coast of the Baltic Sea in Germany in winter 2019, were analysed in order to identify nematode parasites and to compare with recent studies from the same area.

Methods

Endoparasitic nematodes were identified by using both morphological and molecular characters. The successfully obtained sequences of the rDNA marker regions ITS-1, 5.8S, ITS-2 from 29 anisakid and the rDNA marker region ITS-2 of 11 pseudalid nematodes were amplified.

Results

Analyses revealed the presence of three parasite species, the anisakid nematode Contracaecum osculatum from grey seals and the pseudalid nematodes Pseudalius inflexus and Stenurus minor from the harbour porpoises. Other anisakid nematodes regularly occurring in the Baltic Sea, e.g. Anisakis simplex or Pseudoterranova decipiens, were not found.

Conclusions

The prevalence of 100% and a severe parasite load in grey seals demonstrated a very high C. osculatum infection of Baltic Sea fish as their regular prey. Prevalence of 33% for parasites in harbour porpoises and minor infection rates, combined with a distinct lack of anisakid nematodes, are typical for the current situation of the porpoise parasite fauna in the Baltic Sea. Invasive parasite species as possible indicators for climate change could not be detected.