EN
Two species of monogenetic worms of the genus Pseudodactylogyrus, viz., P. bini (Kikuchi, 1929) and P. anguillae (Yin et Sproston, 1948), were recorded on the gills of eel from Strażyn Lake. In order to distinguish these two species the following skeletal elements were examined: length of anchors, length of basal part of anchors, length to the point of anchors, length of anchors except the double bent part of the internal process, length of bar, length of marginal hooks, length of accessory cirrus and length of vagina. Student’s t-test showed statistically significant differences (p<0.01) between some investigated parameters of these two species: length of anchors, length of basal part of anchors, length to point of anchors, length of anchors except the double bent part of the internal process, length of bar and length of marginal hooks. The differences in length of the accessory cirrus and length of vagina were not statistically significant (p = 0.05). The two species have been recorded for the first time in Poland.