Molecular phylogeny provides new insights on the taxonomy and composition of Lyperosomum Looss, 1899 (Digenea, Dicrocoeliidae) and related genera

Lyperosomum Looss, 1899 is one of the largest genera of the Dicrocoeliidae and is one of the best examples of the systematic complexity and taxonomic instability within this family. We present the molecular analyses based on novel sequences of nuclear and mitochondrial genes obtained from 56 isolates of adult flukes and larval stages of dicrocoeliids belonging to Lyperosomum, Skrjabinus, Zonorchis as well as previously available sequence data. According to obtained results we propose to return Zonorchis clathratus and Z. petiolatus into Lyperosomum, and to recognize L. alagesi as a synonym of L. petiolatum. Our study shows that L. petiolatum commonly occurs in Europe in corvids as well as in several species of migratory songbirds, e.g. Sylvia atricapilla. At the same time, the Turdidae appear to host a distinct species of Lyperosomum. The phylogenetic analysis has clearly demonstrated the paraphylepic nature of Lyperosomum and indicated the need of its thorough revision preferably using specimens from type hosts and type territories of nominal species. In addition, inclusion of numerous not yet sequenced dicrocoeliid genera into future phylogenetic studies is necessary to clarify the interrelationships of taxa within the family and stabilize its system

Host-dependent morphology of Isthmiophora melis (Schrank, 1788) Luhe, 1909 (Digenea, Echinostomatinae) – morphological variation vs. molecular stability

Abstract Background Echinostomes are cosmopolitan digenean parasites which infect many different warm-blooded hosts. Their classification is extremely confused; the host spectrum is wide, and morphological similarities often result in misidentification. During our long-term studies on the helminth fauna of rodents and carnivores we have collected 27 collar-spined echinostomes which differ in morphology to an extent that suggests the presence of more than one species. Here, we describe this material, and the extent of host-related variation in this parasite. Methods Specimens of Isthmiophora isolated from four host species (badger, American mink, hedgehog, striped field mouse) were subject to morphological and molecular examination; the data were statistically analysed. Results Our results show that genetically all the Isthmiophora specimens obtained from all the examined hosts are conspecific and represent I. melis. On the other hand, the individuals isolated from Apodemus agrarius are morphologically distinct and, based on this criterion alone, should be described as a new species. Conclusions The morphological traits of Isthmiophora melis are much variable and host-dependent; without molecular analysis they would suggest a necessity to describe a new species or even genus. Such a high level of intraspecific variability may be affected by the host’s longevity

The genetic structure of populations of Isthmiophora melis (Schrank, 1788) (Digenea: Echinostomatidae). Does the host’s diet matter?

Abstract Background Here we provide a comparative analysis of the genetic structure of populations (based on nad1 mtDNA) of Isthmiophora melis isolated from the American mink (Neogale vison), an introduced invasive species, commonly occurring in the territory of Poland, and from the striped field mouse (Apodemus agrarius). Methods A total of 133 specimens of I. melis were obtained from naturally infected N. vison collected from six localities in Poland (108 samples) and 25 individuals of I. melis from A. agrarius. All sequences of the nad1 gene obtained during the present study were assembled and aligned. The standard statistics for haplotype composition, i.e., the number of haplotypes, haplotype diversity, nucleotide diversity, and average number of nucleotide differences, were calculated. Haplotype analysis and visualization of haplotype frequency among populations were performed using a median-joining network. Results Based on the samples collected from different localities in Poland, our study revealed that the overall genetic diversity of I. melis isolated from the American mink and of the striped field mouse do not differ significantly. The median-joining network showed that the three main haplotypes are in the centre of a star-like structure, with the remaining haplotypes as the satellites, reflecting the recent expansion of the populations. Conclusions The overall genetic diversity of I. melis isolated from the American mink and striped field mouse reveals a high level of homogeneity. Moreover, regional differences in the food composition of the definitive hosts play an important role in shaping the genetic structure of the trematode populations. Graphical Abstrac

Parasitic nematodes of the genus Syphacia Seurat, 1916 infecting Muridae in the British Isles, and the peculiar case of Syphacia frederici.

Syphacia stroma (von Linstow, 1884) Morgan, 1932 and Syphacia frederici Roman, 1945 are oxyurid nematodes that parasitize two murid rodents, Apodemus sylvaticus and Apodemus flavicollis, on the European mainland. Only S. stroma has been recorded previously in Apodemus spp. from the British Isles. Despite the paucity of earlier reports, we identified S. frederici in four disparate British sites, two in Nottinghamshire, one each in Berkshire and Anglesey, Wales. Identification was based on their site in the host (caecum and not small intestine), on key morphological criteria that differentiate this species from S. stroma (in particular the tail of female worms) and by sequencing two genetic loci (cytochrome C oxidase 1 gene and a section of ribosomal DNA). Sequences derived from both genetic loci of putative British S. frederici isolates formed a tight clade with sequences from continental worms known to be S. frederici, clearly distinguishing these isolates from S. stroma which formed a tight clade of its own, distinct from clades representative of Syphacia obvelata from Mus and S. muris from Rattus. The data in this paper therefore constitute the first record of S. frederici from British wood mice, and confirm the status of this species as distinct from both S. obvelata and S. stroma