Polymorphism of the median crochets of Dactylogyrus vastator Nyb., 1924 (Monogenoidea) from the crucian carp, Carassius carassius L

There are some variations in the dimensions of anchors depending on the age of the host, localisation and number of parasites. To differentiate such close morphological species as D. vastator and D. crassus it has been suggested to take into account, in addition to taxonomic features, the correlation between the anchor ventroapical length and the bend.