Fig. 1

Scheme of the life cycle of the Psilostomatidae and the stages analyzed. a Complex life cycle of the Psilostomatidae in nature (yellow arrows) and in the laboratory conditions (red arrows); final host in nature are waterfowl, the first and the second intermediate hosts are molluscs Bithynia tentaculata. Chicken was used as final host in laboratory (red silhouette). Redia, metacercaria and adult worm stages are shown inside of their respective hosts. b-g Scanning electron microscope images of life cycle stages of Psilotrema simillimum (b-d) and Sphaeridiotrema pseudoglobulus (e-g). b, e Rediae (parasitic stage of the parthenogenetic generation). c, f Cercariae (free-living larvae of amphimictic generation). d, g Adult worms of the amphimictic generation. Scale-bars: b-e, g, 50 µm; f, 100 µm