Diphyllobothrium sp. and Other Parasites of Migrating and Rare Fish Species in the Southern Baltic Sea and Coastal Waters, Poland.

The present study is the first to analyse the parasite fauna of sole Solea solea, dab Limanda limanda, hake Merluccius merluccius, whiting Merlangius merlangus, and plaice Pleuronectes platessa in the Pomeranian Bay, as well as saithe Pollachius virens from the Szczecin Lagoon (Poland). The aim of this study was to determine the occurrence of parasites in migrating and rare fish in the Pomeranian Bay and the Szczecin Lagoon and to determine the composition of the diet of these fish. The fish for analysis were obtained in the years 2010-2019. The typical marine nematode Capillaria (Procapillaria) gracilis, rarely recorded in Poland, was found, in addition to the following parasites: Ichthyophonus hoferi, Trichodina jadranica, Diphyllobothrium sp., Dichelyne (Cucullanellus) minutus, Raphidascaris acus, Anisakis simplex, Contracaecum osculatum, Hysterothylacium aduncum, Pseudoterranova decipiens, and Echinorhynchus gadi. Because the fish species analysed in the study are not typically present in the Baltic (with the exception of plaice), and because we do not know how long they feed while they are in the Baltic, we cannot be certain which parasites they acquired in the water bodies analysed in the study and which were introduced during the migration of fish. Although these fish are outside of their normal geographic range (except for plaice), in the new environment, there were enough suitable intermediate hosts for the parasites of these fish to complete their life cycle and survive.

Endohelminths of European Perch (Perca fluviatilis) from Selected Localities in Poland with an Emphasis on Search of the Broad Fish Tapeworm Dibothriocephalus latus.

INTRODUCTION: A piscivorous fish European perch (Perca fluviatilis) is present in all types of lakes and brackish waters in Poland. Previous ichthyoparasitological surveys revealed broad spectrum of endohelminths in perch from different aquatic environments. Among them, detection of Diphyllobothrium sp. and Dibothriocephalus latus (syn. Diphyllobothrium latum) in the Pomeranian Bay is of particular interest, since D. latus is one of the causative agents of diphyllobothriasis, fish-borne parasitic zoonosis. Besides, D. latus eggs were previously detected in coprological samples of otter, wolf and lynx from the Bialowieza Primeval Forest. AIM: To conduct parasitological examinations of European perch from the Pomeranian Bay in order to detect the spectrum of its endohelminths and to provide a pilot study on helminths of perch from different water bodies in the Bialowieza Primeval Forest. Due to zoonotic character of D. latus, we have focused our attention to this tapeworm. RESULTS: The larvae of tapeworm Triaenophorus nodulosus and thorny-headed worm Acanthocephalus lucii were detected in perch from the Pomeranian Bay. In perch from different localities in the Bialowieza Primeval Forest, T. nodulosus, A. lucii and tapeworm Proteocephalus percae were detected. D. latus plerocercoids were found neither in musculature nor in peritoneal cavity and other internal organs of any of the fish examined from both studied localities in Poland. CONCLUSION: Future screening implementing morphological and molecular markers is needed in order to understand the current distribution of D. latus in Europe.