Abstract:The present study analysed the taxonomic status and phylogenetic relationships of two species of xiphidiocercariae of the ʻmicrocotylaeʼ group, Cercaria pugnax La Valette St. George, 1855, from Viviparus viviparus (Linnaeus) in the Ukraine and Cercaria helvetica XII Dubois, 1928 from Bithynia tentaculata (Linnaeus) in Lithuania. Molecular phylogenetic analyses based on sequences of the ITS2 region and partial 28S gene of the nuclear rDNA revealed that both these xiphidiocercariae belong to the Lecithodendriidae Lühe, 1901 and represent larval stages of lecithodendriids parasitic in bats. Cercaria helvetica XII clustered with the typical representatives of the genus Lecithodendrium Looss, 1896, being very close, but not identical, to Lecithodendrium linstowi Dollfus, 1931. Sequences of C. pugnax matched exactly the sequences of adult Paralecithodendrium chilostomum (Mehlis, 1831). Morphological descriptions of the cercariae are included; these represent the first report of non-virgulate xiphidiocercariae belonging to the family Lecithodendriidae. Until now, the presence of glandular virgula organ in the region of the oral sucker was considered a robust synapomorphy for the Lecithodendriidae and several closely related families. Our results have shown that the relative importance of this character is in need of a re-assessment.

Three species of bucephalid digeneans are known in European freshwater habitats. In this study parthenitae of Rhipidocotyle campanula (Dujardin, 1845) and R. fennica Gibson, Taskinen & Valtonen, 1992, infecting unionid bivalves, and adult Bucephalus polymorphus von Baer, 1827 from perch (Perca fluviatilis L.) were investigated using karyological analysis and DNA sequencing. Our previously published data on genetic characteristics of parthenitae of B. polymorphus from Dreissena polymorpha Pallas were used for comparative analysis. Ribosomal DNA sequences (ITS2 and 28S rDNA) were used to estimate the phylogenetic relationships of the three bucephalid species. Very close phylogenetic affinity between investigated species was revealed; the sequence difference between the two species of Rhipidocotyle Diesing, 1858 (3.78% based on 28S) was comparable with intergeneric differences observed in comparisons of B. polymorphus with R. campanula and R. fennica (3.43% and 4.49% based on 28S, respectively). A high degree of similarity was noted in karyotype structure of the two species of Rhipidocotyle. The diploid chromosome sets consist of 14 bi-armed chromosomes with the first pair of metacentric elements markedly larger than the remaining chromosomes. This chromosome set structure is also specific to B. polymorphus. One specimen of Anodonta anatina L. was infected with tetraploid R. fennica (4n = 28). On the basis of karyotype characters and molecular data, species of the genus Rhipidocotyle cannot be recognised as more closely related to each other than to B. polymorphus. Our findings of Lithuanian and Ukrainian populations of unionid mussels infected with R. fennica provide evidence that this species occurs not only in Finland but also in Central and Eastern Europe. Previous reports of B. polymorphus in unionids in these regions are equivocal because of possible confusion with R. fennica.

Petkevi ci ut_ e, R., Stun z_ enas, V., Stanevi ci ut_ e, G., Zhokhov, A.E. (2015). European Phyllodistomum (Digenea, Gorgoderidae) and phylogenetic affinities of Cercaria duplicata based on rDNA and karyotypes. 44,[191][192][193][194][195][196][197][198][199][200][201][202] Genetic markers of some European Gorgoderidae species, including potential adults of Cercaria duplicata, were obtained and used to clarify phylogenetic affinities within the genus Phyllodistomum and to verify conflicting data existing on their life cycles. Molecular data and karyotype, 2n = 18, provide further support for ascription of C. duplicata to the Gorgoderinae. Sequences of C. duplicata form a robustly supported major clade, phylogenetically distinct from other known gorgoderid species in both ITS2-and 28S-based phylogenetic trees. The molecular data revealed no match between C. duplicata and any species of Phyllodistomum, including adults found in the experimental studies. One of them, P. elongatum, showed no differences from type species P. folium. Other, P. angulatum, forms a robustly supported clade, which is closely related to P. macrocotyle clade in all phylogenetic trees. This study supports the concept that only P. macrocotyle is a parasite of Dreissena polymorpha among the phyllodistomes and life cycle described for the type species P. folium by Sinitsin (1905) can apparently be discounted. Previously reported low host specificity of P. folium was justified. Adults of P. folium were detected in eight teleost species from five families and four orders. Cystocercous cercariae of P. folium were recorded in sphaeriid bivalves of the genus Sphaerium and Pisidium. According to our molecular data, P. simile, parasite of bullhead, must be regarded as synonym of P. folium. Phyllodistomum umblae is most closely related to P. folium in the all phylogenetic analyses. Molecular phylogenies support a presumption that Phyllodistomum species with cystocercous cercariae developing in sphaeriid bivalves should be regarded as Phyllodistomum sensu stricto. The results reveal a clear need for reconsideration of the knowledge on gorgoderid life cycles based on experimental studies and re-evaluation of the validity of some nominal Phyllodistomum species. Corresponding author: Romualda Petkevi ci ut_ e,

The present work represents the first karyological and molecular characterisation of Sphaerium solidum, a rare European clam. Specimens of S. solidum were collected in Lithuania and Hungary. The modal diploid chromosome number found in both populations was 2n=30. Small, biarmed B chromosomes were found in 42.3% of cells studied in clams from Lithuania and in 11.8% of cells in clams from Hungary. Comparative analysis revealed no significant (P<0.05) interspecific differences in chromosome morphology of S. solidum and that of previously studied S. corneum. DNA sequence analyses of S. solidum showed no interpopulation differences in ITS1; moreover, only one site was different from ITS1 of S. corneum. However, differences in mitochondrial 16S sequence of S. solidum were revealed: two haplotypes in Lithuania and three in Hungary were identified. The genetic characteristics revealed in this study do not support ascription of S. solidum and S. corneum to different subgenus, Cyrenastrum and Sphaerium s. str., respectively. Comparative cytogenetic analysis disclosed that the chromosome morphology could be conserved in some sphaeriid species during speciation despite the fact that most other species in this family undergo radical karyotypic differentiation.

Genetic data were used to examine the diversity in some allocreadiid trematodes. Nuclear ribosomal DNA (ITS2 and partial sequences of 5.8S and 28S) was sampled from sexual adult and 'larval' stages. From these and previous reference datasets phylogenetic trees were constructed. The results uncovered genetically distinct lineages within Bunodera luciopercae (Müller, 1776), suggesting that the two Palaearctic subspecies, B. l. luciopercae and B. l. acerinae Roitman & Sokolov, 1999, and Nearctic B. luciopercae from Perca flavescens may represent distinct species with a restricted host-specificity. Identical rDNA was revealed for the sexual adult of B. l. acerinae and 'larval' B. luciopercae described by Wiśniewski (1958). An unexpected match between the rDNA sequences of adult B. l. luciopercae and 'larval' Allocreadium isoporum (sensu Wiśniewski, 1958) was also detected. The adult A. isoporum (Looss, 1894) differs significantly from the 'larval' A. isoporum, the level of rDNA sequence divergence between them (8.6 % for 5.8S-ITS2-28S sequences and 6.26% for 28S) being consistent with the level expected for intergeneric variation. These results revealed the possible existence of a cryptic species complex within the nominal species B. luciopercae and a clear need for reconsideration of some of the accepted, but largely untested, tenets regarding allocreadiid life-cycles.