The complete mitochondrial genome of Orthocoelium streptocoelium (Digenea: Paramphistomidae) for comparison with other digeneans

Abstract

Orthocoelium streptocoelium is a common paramphistome species parasitizing the rumen and/or reticulum of small ruminants, leading to significant losses. This study first determined the complete mitochondrial (mt) genome of O. streptocoelium. The complete mt genome of O. streptocoelium was amplified, sequenced, assembled, analysed and then compared with those of other digeneans. The entire mt genome of O. streptocoelium is 13,800 bp in length, which is smaller than those of other digeneans except for Opisthorchis viverrini. This mt genome contains 12 protein-coding genes, 22 transfer RNA genes, two ribosomal RNA genes and two non-coding regions. The arrangement of the O. streptocoelium mt genome is the same as those of other digeneans except for Schistosoma haematobium and Schistosoma spindale. Phylogenetic analyses based on concatenated amino acid sequences of the 12 protein-coding genes representing 16 digeneans were conducted to assess the relationship of O. streptocoelium with other digeneans. The result indicated that O. streptocoelium is closely related to Paramphistomum cervi and Fischoederius elongates, which is in accordance with their relationships by taxonomy. This complete mt genome of O. streptocoelium enriched the mitochondrial genome data of paramphistomes and provided important molecular markers for diagnostics and studies of population variation, epidemiology, ecology and evolution of O. streptocoelium and other digeneans.

Characterization of the complete mitochondrial genomes of Diplodiscus japonicus and Diplodiscus mehari (Trematoda: Diplodiscidae): Comparison with the members of the superfamily Paramphistomoidea and phylogenetic implication

“…It indicated that Paramphistomidae and Gastrothylacidae were more closely related than Diplodiscidae. In the group of Paramphistomidae and Gastrothylacidae, the five species of Paramphistomidae did not cluster together, O. streptocoelium formed a separate branch, which is consistent with previous study ( Zhao et al, 2017 ). Interestingly, the further analysis found that the flukes parasitic in amphibians (frogs) formed one group, and the flukes from ruminants (cattle, sheep, ect) clustered together and formed another group.…”

“…There were only one NCR in both D. japonicus and D. mehari , which were similar to D. nigromaculati (MW698822). However, this was different from other trematodes in superfamily Paramphistomoidea, such as F. cobboldi , O. streptocoelium , G. crumenifer , P. cervi , P. leydeni and F. elongatus , which had two NCRs ( Yan et al, 2013 ; Ma et al, 2015 ; Yang et al, 2016 ; Zhao et al, 2017 ; Han et al, 2020 ). In Paramphistomoidea trematodes, the longest overall NCR length was G. crumenifer (813 bp) and the shortest overall NCR length was O. streptocoelium (310 bp).…”

“…Individual gene lengths vary from 56 bp to 74 bp ( Table 1 ). The lengths of D. japonicus and D. mehari tRNA were similar with to those of P. cervi (59–72 bp), P. leydeni (59–73 bp), G. crumenifer (59–72 bp), and O. streptocoelium (59–72 bp) ( Yan et al, 2013 ; Ma et al, 2015 ; Yang et al, 2016 ; Zhao et al, 2017 ), which suggested that tRNA gene size has changed quite slowly during trematode evolutionary divergence. All tRNA sequences could be folded into the typical cloverleaf structure, except trn S1, which lacked the dihydrouridine (DHU) arm in both Diplodiscus mitogenomes ( Fig.…”

“…Among the 12 PCGs, the length of cox 1 in D. mehari was 1,572 bp, which was the longest than those of other Paramphistomoidea trematodes, including D. japonicus (1,548 bp), D. nigromaculati (1,548 bp), F. elongatus (1,542 bp), F. cobboldi (1,542 bp), G. crumenifer (1,542 bp), C. microbothrioides (1,542 bp), O. streptocoelium (1,542 bp), P. cervi (1,542 bp), P. leydeni (1,542 bp) and E. explanatum (1,547 bp) ( Table 2 ). Moreover, the nad 4 genes of three Diplodiscus species ( D. japonicus , D. mehari and D. nigromaculati ) with length of 1287 bp, were 6 bp longer than those of others in the same superfamily ( Yan et al, 2013 ; Ma et al, 2015 ; Yang et al, 2016 ; Zhao et al, 2017 ; Han et al, 2020 ).…”

Calicophoron daubneyi (Digenea: Paramphistomidae): The efficacy of anthelmintics in naturally infected cattle

“…Rumen flukes infect ruminants and consist of a number of different species of the Paramphistomidae family (Gunathilaka et al, 2018). This family includes, for example, the genus Paramphistomum, Calicophoron, Cotylophoron, Ceylonocotyle, Gastrothylax, Fischoederius, Carmyerius, Gastrodiscus and Pseudodiscus (Torres-Acosta et al, 2012;Zhao et al, 2017;Kotze et al, 2020). Rumen fluke parasites impact hugely on livestock productivity by affecting growth rates, fertility, meat quality, wool or milk production, and they sometimes cause mortality.…”