We investigated the spatial distribution and measured the hard parts of the attachment apparatuses and reproductive organs of the 2 eel-specific monogenean species Pseudodactylogyrus anguillae and Pseudodactylogyrus bini. Comparative analysis focused on parasite microhabitats within the gill apparatus. Additionally, we compared the morphometric characteristics of the monogeneans based on geographical locality and seasonality. The attachment apparatus and reproductive organ characteristics of the monogeneans were similar in all gill apparatus microhabitats. However, measurements differed significantly between localities and between seasons, with the results suggesting that abiotic factors play a larger role in determining parasite morphology than do the gill microhabitats.