Helminth Parasites of the Three-spined Stickleback Gasterosteus aculeatus L., 1758 (Actinopterygii: Gasterosteidae) from a Black Sea Coastal Wetland, Bulgaria

Totally, 134 individuals of Gasterosteus aculeatus from the Lake Atanasovsko Wetland, Bulgaria, were examined for helminth parasites. Five helminth species were identified: the trematode Posthodiplosto-mum brevicaudatum (metacercariae), the monogenean Gyrodactylus arcuatus, the trypanorhynch cestode Progrillotia dasyatidis (plerocerci) and third-stage larvae of the ascaridoid nematodes Contracaecum sp. and Hysterothylacium sp. Of them, G. arcuatus was the most prevalent species, with prevalence (P%) 68.66, followed by P. brevicaudatum (P% 22.39). The remaining species were weakly represented: Hys-terothylacium sp. (P% 4.48), P. dasyatidis (P% 3.73) and Contracaecum sp. (P% 0.75). The present study is the first record of G. aculeatus as a host of a species of Contracaecum from the Black Sea basin. Gyro-dactylus arcuatus is a new record for the Bulgarian fauna.