Accepted_test
The ITS2 rRNA spacer region were obtained for previously described trematodes: Echinochasmus pseudobeleocephalus (2023), Sphaeridiotrema ussuriensis, S. aziaticus,
S. pyriforme, and Psilotrema limosum (2022). Sequence analysis of ITS2 was performed to see if there was interspecies variation. Phylogenetic analysis of the full sequence ITS2 was performed using Bayesian inference (BI) and maximum likelihood (ML) algorithms. The work compared ITS2 sequences from 66 species. These species cover 7 families: Echinostomatidae, Echinochasmidae, Psilostomatidae, Fasciolidae, Eucotylidae, Philophthalmidae, Cyclocoelidae. The sequences vary in length from 235 to 1002 bp. Secondary structure folding predicted a four-domain model with only the A and B domains conserved. The phylogenetic tree based on the sequences of the ITS2 rDNA region is similar to previously obtained data on the 28S rRNA gene by Tkach and co-authors (2016).