Species communities found on the stone crayfish in the study area: (a) summer and (b) autumn. Numbers indicate average species abundances at a site based on the mean. B.para = Branchiobdella parasita, B.hexa = Branchiobdella hexadonta, B.penta = Branchiobdella pentadonta, B.balc = Branchiobdella balcanica, H.chapp = Hystricosoma chappuisi, N.comm = Nais communis; for study site abbreviations see Table 1. ^* = H. chappuisi summer abundances are qualitative.