Life cycle, morphology of developmental stages ofMetorchis ussuriensissp. nov. (Trematoda: Opisthorchiidae), and phylogenetic relationships with other opisthorchiids

Abstract

The complete life cycle and developmental stages of the fluke, Metorchis ussuriensis sp. nov. (Trematoda, Platyhelminthes), are herein described. The results of the present experiments showed that, for flukes from the Primorsky Region in the Russian southern Far East, the first intermediate hosts are the snails Parafossarulus spiridonovi and Boreoelona ussuriensis, and the second intermediate hosts are freshwater fish, tadpoles, and snails. The definitive host in this experiment was Anas platyrhynchos dom. Morphometric parameters of M. ussuriensis sp. nov. demonstrate similarities with Metorchis taiwanensis, but the two species differ in the sizes of their bodies, sizes of suckers of adult worms, and sizes of cercariae, as well as respective positions of the finfold in cercariae. Phylogenetic reconstructions and genetic distances using the cox1 gene sequences support the conclusion that M. ussuriensis sp. nov. is well distinguished from all other species of the genus Metorchis, while sequences of internal transcribed spacers (ITS1 and ITS2) failed to separate M. ussuriensis sp. nov., Metorchis bilis, and Metorchis xanthosomus. In addition, we sequenced 1,402 bp of the 28SrRNA gene of M. ussuriensis sp. nov. being the first 28S sequences in the genus Metorchis. Comparison to other trematodes suggests that 28SrRNA could proof suitable for the differentiation of trematode species.

Echinostoma chankensis nom. nov., other Echinostoma spp. and Isthmiophora hortensis in East Asia: morphology, molecular data and phylogeny within Echinostomatidae

“…S5, 6). However, it must be taken into account that the nucleotide sequences of this gene have different rates of mutation accumulation in closely related species of trematodes, as shown by the analysis of this mitochondrial marker for the family Opisthorchiidae Looss, 1899 (Sitko et al ., 2016; Besprozvannykh et al ., 2019). Due to the non-uniform rate of nucleotide substitutions in the nad1 marker, there may be both a high value of genetic distances and the absence of any differences between some close species, or differences there are minimal.…”

Three species of Exorchis Kobayashi, 1921 (Digenea: Cryptogonimidae) in the East-Asian region: morphological and molecular data

“…Amplicons were sequenced using an ABI 3500 Genetic Analyser (Applied Biosystems; at the Federal Scientific Center of the East Asia Terrestrial Biodiversity FEB RAS, Russia). For sequencing, external and internal primers are used: BD2 for ITS2 ; DIGl2, 900F (5′-CCG-TCT-TGA-AAC-ACG-GAC-CAA-G-3′, forward, Tkach et al ., 2003), 1200R (5′-CTT-GGT-CCG-TGT-TTC-AAG-ACG-GG-3′, reverse, Tkach et al ., 2003), 28S4R (5′-TAT-TTA-GCC-TTG-GAT-GGA-GTT-TAC-C-3′, reverse, Besprozvannykh et al ., 2019) for 28S , and Co1-Fw, Co1-Rv for cox 1. The cox 1 gene of metacercariae in Japan is amplified and sequenced using the following primers: JB3 (5′-TTT-TTT-GGG-CAT-CCT-GAG-GTT-TAT-3′, forward) and CO1-R trema (5′-CAA-CAA-ATC-ATG-ATG-CAA-AAG-G-3′, reverse) (Miura et al ., 2005).…”

“…n. (7.1–7.4%), which is located at a basal position of the tree. These values are comparable to interspecies genetic distances between representatives of related families, namely Opisthorchiidae Looss, 1899 and Heterophyidae Leiper, 1909 (Tatonova et al ., 2018; Besprozvannykh et al ., 2019). Fixed amino acid substitutions have also been identified between analysed species (Fig.…”

Taxonomic myths and phylogenetic realities in the systematics of the Opisthorchiidae (Trematoda)

“…The ribosomal ITS1-5.8S-ITS2 fragment was amplified with the primers ITSF (5′-CGC CCG TCG CTA CTA CCG ATT G-3′) (Andres et al, 2018) and S4R (5′-TAT GCT TAA ATT CAG CGG GT-3′) (Besprozvannykh et al, 2019) at an annealing temperature of 54°C.…”