Streptocara formosensis Sugimoto, 1930 (Nematoda: Acuariidae) in wild ducks from the southern coast of the Baltic Sea

Summary

Although nematofauna of wild ducks in north-western Poland seems to be quite well known, researchers still discover species that are new for the fauna of this region and Europe in general. One of them is Streptocara formosensis Sugimoto, 1930 with distinct ecological specificity (the nematode parasites only ducks wintering in the southern Baltic Sea) and topospecificity (limited to the gizzard). During parasitological research on 1005 wild ducks representing 17 species, 13,333 nematodes were isolated, 360 of which (2.7 %) were identified as Streptocara formosensis Sugimoto, 1930. The distinguishing feature of this species from other nematodes of the genus Streptocara (Railliet, Henry and Sisoff, 1912) is the absence of a collar and a specific arrangement of deirids at the nerve ring. During the study, the nematodes were located only under the stratum corneum of the gizzard, lying down in the form of characteristic white “springs.” This is the first observation of this parasite in the nematofauna of Polish wild birds. The nematode was found in 84 (8.35 %) wild ducks representing 7 species: Aythya Marila (Aythyini), Bucephala clangula, Clangula hyemalis, Melanitta nigra, M. fusca, Mergus merganser, Mergellus albellus (Mergini). The highest prevalence (36.7 %) occurred in mergansers; the coefficient of dominance showed that S. formosensis is a subdominant species in B. clangula, C. hyemalis and M. merganser, and a rare species in other hosts. The presence of the parasite in only three out of 157 examined A. marila suggests that the greater scaup is only an accidental host for the nematode.