Description and Phylogenetic Relationships of Pojmanskatrema balcanica n. gen., n. sp. (Digenea: Dicrocoeliidae) from the Eurasian Water Shrew Neomys fodiens (Mammalia: Soricidae) in Bulgaria

Chelatrematidae n. fam., a new family of digenetic trematodes from the South Western Ghats, India, erected on the basis of morphological and molecular studies

On the basis of the morphological characterization of Chelatrema neilgherriensis Manjula & Janardanan, 2006 recovered from the freshwater fish Barilius gatensis (Valenciennes, 1844) in the Wayanad region of the Western Ghats, the diagnostic features of the genus Chelatrema Gupta & Kumari, 1973 have been modified. Based on the phylogenetic analysis of C. neilgherriensis and comparative morphology studies relative to members of other families of Gorgoderoidea Looss, 1901, this genus is placed in a new family Chelatrematidae n. fam. The studies revealed the molecular and morphological closeness of Chelatrema with Paracreptatrematina limi Amin & Myer, 1982, and the latter is transferred to this new family. Hence the new family Chelatrematidae n. fam. comprises the genera Chelatrema and Paracreptatrematina.

New dicrocoeliid digeneans from mammals in Ecuador including a highly genetically divergent new genus from an ancient marsupial lineage

The Dicrocoeliidae is a highly diverse and broadly distributed family of digeneans typically parasitic in the gall bladder and liver of their tetrapod hosts. So far, no study has reported dicrocoeliids, or any digeneans, from the ancient marsupial family Caenolestidae. Herein, we describe a new genus of dicrocoeliids (Otongatrema n. gen.) from Tate's shrew opossum Caenolestes fuliginosus and a new species of Metadelphis (Metadelphis cesartapiai n. sp.) from a phyllostomid bat Anoura peruana collected in Ecuador. Otongatrema can be readily distinguished from the morphologically closest dicrocoeliid genera Concinnum, Conspicuum and Canaania based on the position of the genital pore, distribution/position of the uterus and extent of vitellarium. Metadelphis cesartapiai can be easily differentiated from other Metadelphis spp. based on a combination of morphological characters including body shape and size, distribution of vitellarium, shape of the gonads as well as size of suckers and cirrus sac. In addition, we used newly generated partial sequences of the nuclear 28S rRNA gene and mitochondrial cox1 genes to examine phylogenetic affinities of the new taxa within the Dicrocoeliidae. Both the 28S and cox1 phylogenies confidently positioned Otongatrema as a sister/basal group to all other dicrocoeliids sequenced so far. The phylogenetic position of Otongatrema may be explained by a close co-evolutionary relationship with Caenolestidae, one of the most basal and most ancient groups of marsupials. In addition, our 28S phylogeny provides evidence that the complete or partial loss of intestinal structures has likely occurred independently at least 3 times in the evolutionary history of the Dicrocoeliidae.

Molecular phylogenetics and mitogenomics of three avian dicrocoeliids (Digenea: Dicrocoeliidae) and comparison with mammalian dicrocoeliids

Background

The Dicrocoeliidae are digenetic trematodes mostly parasitic in the bile ducts and gall bladder of various avian and mammalian hosts. Until recently their systematics was based on morphological data only. Due to the high morphological uniformity across multiple dicrocoeliid taxa and insufficient knowledge of relative systematic value of traditionally used morphological characters, their taxonomy has always been unstable. Therefore, DNA sequence data provide a critical independent source of characters for phylogenetic inference and improvement of the system.

Methods

We examined the phylogenetic affinities of three avian dicrocoeliids representing the genera Brachylecithum, Brachydistomum and Lyperosomum, using partial sequences of the nuclear large ribosomal subunit (28S) RNA gene. We also sequenced the complete or nearly complete mitogenomes of these three isolates and conducted a comparative mitogenomic analysis with the previously available mitogenomes from three mammalian dicrocoeliids (from 2 different genera) and examined the phylogenetic position of the family Dicrocoeliidae within the order Plagiorchiida based on concatenated nucleotide sequences of all mitochondrial genes (except trnG and trnE).

Results

Combined nucleotide diversity, Kimura-2-parameter distance, non-synonymous/synonymous substitutions ratio and average sequence identity analyses consistently demonstrated that cox1, cytb, nad1 and two rRNAs were the most conserved and atp6, nad5, nad3 and nad2 were the most variable genes across dicrocoeliid mitogenomes. Phylogenetic analyses based on mtDNA sequences did not support the close relatedness of the Paragonimidae and Dicrocoeliidae and suggested non-monophyly of the Gorgoderoidea as currently recognized.

Conclusions

Our results show that fast-evolving mitochondrial genes atp6, nad5 and nad3 would be better markers than slow-evolving genes cox1 and nad1 for species discrimination and population level studies in the Dicrocoeliidae. Furthermore, the Dicrocoeliidae being outside of the clade containing other xiphidiatan trematodes suggests a need for the re-evaluation of the taxonomic content of the Xiphidiata.

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.