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Maps of catchments of the watercourses in which the described crayfish mass mortalities occurred. Relevant watercourses and their tributaries are highlighted. Geographic names mentioned in the descriptions of the outbreaks are indicated by abbreviations (water courses and bodies in blue, settlements in black). Potential migration barriers are indicated in the maps, and sites where crayfish affected by mass mortalities were found are highlighted. In case the mass mortality is marked by a single symbol, it is placed at the exact site where crayfish were found; if the extent of mass mortalities is marked by multiple symbol, these are spread over the area of the outbreak (which affected also the regions between such symbols). The same distinction between single and multiple symbols should be made if sites of crayfish presence are indicated on the map.

BackgroundLymnaea palustris and L. fuscus are members of the European stagnicolines (Gastropoda: Lymnaeidae). The role of stagnicolines in transmission of Fasciola hepatica has been often proposed. To assess the possible relationship between these two stagnicolines and F. hepatica in Sweden, field monitoring in parallel with experimental infections of L. palustris and L. fuscus were conducted.MethodsStagnicoline snails were collected and identified on pastures grazed by either sheep or cattle on four farms suffering from fasciolosis in Sweden during 2011–2012. Field-collected L. palustris and L. fuscus were examined for F. hepatica DNA by PCR. In the laboratory, different age groups of L. palustris, L. fuscus and G. truncatula were each exposed to two F. hepatica miracidia and main infection characteristics were obtained.ResultsOne field-collected L. palustris (out of n = 668) contained F. hepatica as determined by PCR. On the other hand, stagnicolines artificially exposed to F. hepatica miracidia resulted in successful infection with fully differentiated cercariae, but only in juvenile snails (size, 1–2 mm at exposure) and with a prevalence of 51% and 13% in L. palustris and L. fuscus, respectively. In contrast, 90% of juvenile (size, 1–2 mm) and 92% of preadult G. truncatula (size, ≥ 2-4 mm), respectively, were successfully infected. Delayed, reduced and/or no spontaneous cercarial shedding was observed in the two stagnicolines when compared to G. truncatula. However, at snail dissection most cercariae from L. fuscus and L. palustris were able to encyst similarly to those from G. truncatula.ConclusionBoth L. fuscus and L. palustris can sustain larval development of F. hepatica but with an apparent level of age resistance. The finding of a single F. hepatica positive specimen of L. palustris, together with infection characteristics from the experimental infection, suggest that L. palustris is a more suitable snail vector of F. hepatica than L. fuscus. The reduced growth observed in both stagnicolines was contrary to the ‘parasitic gigantism’ theory. Overall, it seems that the epidemiological role of L. palustris in transmission of F. hepatica in Sweden is likely to be much lower than for G. truncatula.

Several studies have suggested that aquatic microcrustaceans are relatively efficient dispersers in a variety of landscapes, whereas others have indicated dispersal limitation at large spatial scales or under specific circumstances. Based on a survey of a set of recently created ponds in an area of approximately 18×25 km, we found multiple indications of dispersal limitation affecting the community assembly of microcrustacean communities. Spatial patterns in the community composition were better explained by the geomorphological structure of the landscape than by mere geographic distances. This suggests that ridges separating the network of valleys act as dispersal barriers, and as such may channel the dispersal routes of the studied taxa and, likely, of their animal vectors as well. Dispersal limitation was further supported by a strong positive relationship between species richness and the abundance of neighbouring water bodies, suggesting that isolation affects colonization rates. Finally, the apparent dispersal limitation of microcrustaceans is further corroborated by the observation of low colonization rates in newly dug experimental ponds in the study area.

Freshwater truncatelloidean gastropods include numerous minute cryptic species, displaying simple morphologies, all of which hampers their taxonomic research based on morphology. Phylogenetic relationships among all but one extant species of the genus Kerkia from five localities in Croatia and one in Slovenia were therefore analysed based on one mitochondrial (cytochrome c oxidase subunit I) and three nuclear markers (18S, 28S and H3). Kerkia kusceri (Bole, ), K. jadertina Kuščer, 1933, K. j. sinjana (Kuščer, 1933), and K. kareli Beran, Bodon et Cianfanelli, 2014, were collected from their type localities. Our analysis confirmed their distinctness, recovering two additional clades that may represent yet undescribed species from Croatia. Apart from Kerkia, Hauffenia media Bole, , H. subpiscinalis (Kuščer, 1932) and H. erythropomatia (Hauffen, 1856) from Slovenia were analysed. Their distinctness together with the rejection of the eligibility for separate genus Erythropomatiana for the latter species was proven. Interestingly, its sequence divergence exceeded all previous estimates for species‐level divergence within the Truncatelloidea, implying a species‐level separation both for the COI and for nuclear loci. High p‐distances for the COI/nuclear loci (0.128/0.027, respectively) confirmed also the uniqueness of both genera. A comparison of their COI sequences with the reference sequences of Alzoniella Giusti et Bodon, 1984, Avenionia Nicolas, 1882, Fissuria Boeters, 1981, and Agrafia Szarowska et Falniowski, 2011, has shown that Kerkia and Hauffenia are not sister clades. The most striking, however, was the apparent introgression of the ‘Hauffenia’ mtDNA type from central Slovenia (cave Babja luknja) into two Kerkia clades from central (Ljubač) and southern (Podgrađe) Croatia, that are located 210 km and 360 km away, respectively. The introduced ‘Hauffenia’ mtDNA type and the closest Hauffenia erythropomatia COI differed by 0.8%. Secondary loss of isolating mechanisms between phylogenetically distant organisms and the severe lack of information on distribution of these underground taxa were postulated as possible explanations of this interesting phenomenon.