Redescription and Variability of Polystoma Mazurmovici and P. skuratovitchi (Monogenea, Polystomatidae), with a Key to Polystoma from Anurans of Ukraine

New distributional records for Polystoma mazurmovici Buchvarov, 1980 from Rana dalmatina Fitzinger in Bonaparte, 1839 and P. scuratovitchi Buchvarov, 1984 from Rana arvalis Nicolsson, 1842 reported for the Ukrainian territory of Europe. P. mazurmovici and P. skuratovitchi confirmed as valid species, though their original descriptions were very brief and based on a mixed sub-adult and adult individuals. Metrical data of these species together with new morphological information are provided and incorporated in a dichotomous key to adult Polystoma from anurans of Ukraine. Redescription of an adult form of P. skuratovitchi and descriptions of sub-adult forms of P. mazurmovici and P. skuratovitchi are provided. Study confirms strict host specificity of polystomes and increases the number of already known species of Polystoma of Ukrainian fauna to four