There is very little information on the genus Branchiobdella and the species relationships with their freshwater crayfish hosts inCroatia. Therefore, a base-line study was needed so that future changes in available habitat brought about by urban developmentand the probable introduction of non-native species can be accurately assessed. This investigation used preserved freshwatercrayfish collected from across Croatia between 1995 and 2005 as its source of the ectosymbionts. Crayfish species includedAstacus astacus, A. leptodactylus, Austropotamobius pallipes, A. torrentium, and the allochtonous North American species,Orconectes limosus. Only native European species of branchiobdellids were found: Branchiobdella astaci, B. parasita, B.pentodonta, B. hexodonta, B. italica, and B. balcanica, and this is the first report on the occurrence of these species, apart from B.italica, in Croatia. The distribution of these branchiobdellidans is compared with climatic and river drainage systems, andliterature reports of populations in other countries in the region.
