Abstract
PurposeEndoparasitic 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.MethodsEndoparasitic 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.ResultsAnalyses 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.ConclusionsThe 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.
Highlights
The Baltic Sea, a geologically young habitat [1], is inhabited by four species of marine mammals, not including vagrant species
Based on extensive molecular analysis, this study aims to continue the ongoing research on nematode parasites of Baltic Sea marine mammals, describing their infection with some nematode species, evaluating changes in the parasite loads and composition in pinnipeds and cetaceans by increased grey seal populations and higher infection rates in cods and other potential hosts
Reports indicate that the re-population of the Baltic Sea with grey seals closed the life cycle of C. osculatum after a decade-long absence from the region
Summary
The Baltic Sea, a geologically young habitat [1], is inhabited by four species of marine mammals, not including vagrant species. The only cetacean reproducing inside the Baltic Sea is the harbour porpoise (Phocoena phocoena (L.)). The grey seal is the largest marine mammal living in the Baltic Sea. Halichoerus grypus can reach 165 to 210 cm in length and 250 kg in weight. The species shows a broad prey spectrum, including other marine mammals, while the diet in the Baltic Sea is dominated by only a few fish species [4,5,6,7]. Their diet changes with age [8, 9]
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