First next-generation sequencing data for Haploporidae (Digenea: Haploporata): characterization of complete mitochondrial genome and ribosomal operon for Parasaccocoelium mugili Zhukov, 1971.

The first data on a whole mitochondrial genome of Haploporidae, Parasaccocoelium mugili (Digenea: Haploporata: Haploporidae) was generated using the next-generation sequencing (NGS) approach. We sequenced the complete mitochondrial DNA (mtDNA) and ribosomal operon of Parasaccocoelium mugili, intestine parasite of mullet fish. The mtDNA of P. mugili contained 14,021 bp, including 12 protein-coding genes, two ribosomal genes, 22 tRNA genes, and non-coding region. The ribosomal operon of P. mugili was 8308 bp in length, including 18S rRNA gene (1981 bp), ITS1 rDNA (955 bp), 5.8S rRNA gene (157 bp), ITS2 rDNA (268 bp), 28S rRNA gene (4180 bp), and ETS (767 bp). We used the mtDNA protein-coding regions to make phylogenetic reconstructions of Haploporidae. Additionally, we performed the sequence cluster analysis based on codon usage bias of most of currently available mitochondrial genome data for trematodes. The observed gene arrangement in mtDNA sequence of P. mugili is identical to those of Plagiorchis maculosus (Rudolphi, 1802). Results of maximum likelihood (ML) phylogenetic analysis showed that P. mugili was closely related to Paragonimus species from the suborder Xiphidiata. The results of sequence cluster analysis based on codon usage bias showed that P. mugili has the highest similarity with Plagiorchis maculosus (Xiphidiata). Our results do not contradict to proposing a new suborder for Haploporoidea-Haploporata. On the basis of obtained results, the relationship between mitochondrial protein-coding gene rearrangements and synonymous nucleotide substitutions in mitochondrial genomes has been suggested.

Amended diagnosis, validity and relationships of the genus Acrolichanus Ward, 1917 (Digenea: Allocreadiidae) based on the 28S rRNA gene, and observations on its lineage diversity.

Adult specimens of the allocreadiid trematode Acrolichanus auriculatus (Wedl, 1858) were collected from Acipenser schrenckii Brandt from the River Amur and Amur Estuary, Acipenser ruthenus L. from the Rivers Irtysh and Oka (Asian and European parts of Russia, respectively), and Acipenser fulvescens Rafinesque from Lake Winnebago, Wisconsin, USA, and used for phylogenetic analyses based on 28S rDNA sequence data. The results supported the monophyly of Acrolichanus populations from both continents and a clear separation of A. auriculatus from other allocreadiid taxa, thus supporting the validity of the genus Acrolichanus Ward, 1917. This study formally reestablishes the genus Acrolichanus. Species of this genus differ from other allocreadiids by the following combination of morphological features: triangular mouth opening with rounded posterior corners, simple ventral, dorsolateral and dorsomedian muscular lobes on the oral sucker, stout cirrus-sac, pars prostatica with dorsal pocket, and massive cirrus with conspicuous triradiate lumen when invaginated. Specimens of the trematode from North America and the Rivers Irtysh and Oka were more closely related to each other than to the specimens from River Amur and Amur Estuary. This reflects the evolutionary divergence among sturgeons into Pacific and Atlantic clades. The phylogenetic analyses also confirmed the paraphyly of the genus Crepidostomum Braun, 1900.

Population genetic analysis of trematode Parasaccocoelium mugili Zhukov, 1971 (Haploporidae Nicoll, 1914) from the Russian Far East and Vietnam based on ribosomal ITS and mitochondrial COI gene partial sequence data.

Intraspecific variation of Parasaccocoelium mugili collected from mullet fish of the south of Russian Far East and Vietnam has previously been estimated on the basis of two molecular markers: ribosomal internal transcribed spacer 1 (ITS1) rDNA and mitochondrial cytochrome oxidase I (COI) gene sequences. In the present study, molecular identification of this species from the Kievka River, Primorye and from Vietnam was performed by analysis of 28S rDNA sequences. Analysis of ITS1 rDNA sequences variation revealed two highly differentiated main groups, representing trematode specimens from the two regions. Genetic variation within each region was relatively low. Mitochondrial COI gene sequence data analysis revealed fixed nucleotide and amino acid substitutions, and supported the existence of two genetically different groups associated with geographical origin. Analysis of the COI gene fragments showed extremely high variation within Russian and Vietnamese P. mugili samples. Our results for P. mugili most probably represent a case of initial step of allopotric speciation for this trematode, caused by living strategy of its definitive host at evolutionary scale. Mitochondrial DNA sequence data show that existence of gene flow between local populations of P. mugili in the Primorye Region caused by definitive hosts can be proposed.

Correction to: Morphometric and molecular analyses of Carassotrema koreanum park 1938 and Elonginurus mugilus Lu 1995 (Digenea: Haploporidae) Srivastava, 1937 from the Russian Far East and Vietnam.

The original version of this article contained mistake in the accession number found in Table 1. Correct accession numbers are presented here.

Morphometric and molecular analyses of Carassotrema koreanum Park 1938 and Elonginurus mugilus Lu 1995 (Digenea: Haploporidae) Srivastava, 1937 from the Russian Far East and Vietnam.

Adult worms that belong to Carassotrema Park 1938 and Elonginurus Lu, 1955 were found in the intestine of Carassius gibelio Bloch, 1782 from the southern Russian Far East and Mugil cephalus Linnaeus, 1758 from northern Vietnam, respectively. Morphometric parameters, geographic location and host species composition of these worms correspond to Carassotrema koreanum Park 1938, which is a known parasite of cyprinid fish in Korea, Japan and China, and Elonginurus mugilus Lu, 1955, first described from M. cephalus in China. The validity of Carassotrema ginezinskajae Kulakova, Ha Ky, 1976, a synonym of C. koreanum, first described from Spinibarbichthys denticulatus Oshima, 1926 in Vietnam, supported the morphometric data. Phylogenetic analysis based on combined ITS2 ribosomal DNA (rDNA) and 28S rRNA indicated that C. koreanum and E. mugilus belong to the subfamily Waretrematinae and are closely related to the genera Skrjabinolecithum and Parasaccocoelium, respectively. Species similarity, revealed through molecular analysis, agreed with the generic diagnoses for Parasaccocoelium and Elonginurus, as well as for Carassotrema and Skrjabinolecithum.

Phylogenetic analysis of the superfamily Hemiuroidea (Platyhelminthes, Neodermata: Trematoda) based on partial 28S rDNA sequences.

In the present paper, the phylogenetic relationships between genera, subfamilies and families of the Hemiuroidea are explored. Twelve new sequences of 28 rDNA and data taken from GenBank (NSBI) on 43 species affiliated to 34 genera were included in the analysis. Most of the hemiuroidean trematodes form two highly supported clades (A and B), which are sister groups to each other. Hemipera manteri joined with Gonocerca spp. with moderate statistical support. This clade is basal relative to the clades A and B. Сlade A is polytomic and contains representatives of the families Accacoeliidae, Syncoeliidae, Didymozoidae, Hirudinellidae and Sclerodistomidae, and derogenid subfamilies Derogeninae and Halipeginae. At the same time, the Syncoeliidae, Hirudinellidae and Accacoeliidae form a well-supported monophyletic group. The phylogenetic relationship between Derogeninae and Halipeginae is poorly resolved. Сlade B unites the isoparorchiid, bunocotylid, lecithasterid and hemiurid trematodes. Our data re-establishes the family Bunocotylidae, which consists of two subfamilies, Opisthadeninae and Bunocotylinae, and the Machidatrema chilostoma + Hysterolecithoides frontilatus group. The Bunocotylidae is the sister group to the Hemiuridae + Lecithasteridae group and the Isoparorchiidae is a basal relative to the representatives of these three hemiuroid families.

Phylogenetic position of the genus Gonocerca Manter, 1925 (Trematoda, Hemiuroidea), based on partial sequences of 28S rRNA gene and a reconsideration of taxonomic status of Gonocercinae Skrjabin et Guschanskaja, 1955.

Adult trematodes of the genus Gonocerca Manter, 1925, are parasites of marine fishes. Identification of the phylogenetic positions and a revision of the taxonomic status of the subfamily Gonocercinae Skrjabin et Guschanskaja, 1955 (Derogenidae) are the main purposes of this research article. Four Gonocerca species were used in the study, including the type-species G. phycidis Manter, 1925. Molecular phylogenetic analysis, based on partial sequences of 28S rRNA gene, revealed that Gonocerca spp. are phylogenetically distant from other hemiuroid trematodes, including Derogenes varicus (Müller, 1784), representative of the type-genus of the family Derogenidae. The taxonomic rank of Gonocercinae should be raised to the family level. The generic composition of the family Gonocercidae Skrjabin et Guschanskaja, 1955 stat. nov., requires further clarification as the molecular data do not support the inclusion of the genus Hemipera Nicoll, 1913, in this family.

The life cycle of Asymphylodora perccotti sp. n. (Trematoda: Lissorchiidae) in the Russian Southern Far East.

Specimens of Asymphylodora perccotti sp. n. (Trematoda: Lissorchidae) were found in the esophagus of the freshwater fish Perccottus glenii (Odobantidae) taken from the Bolshaya Ussurka River Basin (Primorsky Region, Russian Southern Far East). The first intermediate host of this trematode is a gastropod, Parafossarulus manchouricus, and the secondary hosts are the same mollusk and Boreoelona ussuriensis. Specimens of the new species are similar to A. amnicolae identified by Stunkard in 1959, but the mature worms have larger suckers and shorter ceca. The cercariae of these species are distinguished by body, suckers and pharynx size. These organs in A. perccotti sp. n. are more than one-third larger than what is observed in A. amnicolae. In addition, the new species lacks the capacity for progenesis. Finally, the new species is unusual in that it resides in the fish esophagus instead of the intestine, as is common for most Asymphylodora species. Partial ribosomal DNA sequences and phylogenetic reconstruction sequence data indicate that these worms represent a new digenean species.