Redescription, complete mitochondrial genome and phylogenetic relationships of Hexostoma thynni (Delaroche, 1811) Rafinesque, 1815 (Monogenea, Hexostomatidae)

Abstract

Specimens of Hexostoma thynni (Delaroche, 1811) Rafinesque, 1815 were collected from their type-host, the bluefin tuna Thunnus thynnus, caught off Algeria, i.e. close to the type-locality, off Mallorca, which is also in the Mediterranean. The species is briefly redescribed and compared to previous descriptions, under the same name or as its synonym Plagiopeltis duplicata Diesing, 1858, to ascertain identity of specimens. The three genera within the Hexostomatidae (Hexostoma Rafinesque, 1815, Neohexostoma Price, 1961 and Homostoma Unnithan, 1965) are briefly discussed, with comments on the fragility of characters used to distinguish them. Using next-generation sequencing, the complete mitogenome and the cluster of ribosomal genes (SSU, LSU, ITS1, ITS2, 5.8S) were obtained. The mitogenome is 14,649 bp long and codes for 12 protein-coding genes, 2 ribosomal RNA genes and 22 transfer RNA genes; its size is similar to other mitogenomes obtained from polyopisthocotylean monogeneans. A phylogeny based on concatenated mitogenome protein-coding genes from nine species of polyopisthocotylean monogeneans produced a tree in which the Hexostomatidae H. thynni was associated with other Mazocraeidea, such as Chauhaneidae and Diclidophoridae. This invalidates the hypothesis of Boeger & Kritsky (1993) of Hexostomatidae as sister-group to the Mazocraeidea and suggests the demise of the suborder Hexostomatinea Boeger & Kritsky, 1993. We insist on the usefulness of depositing parts of specimens used for molecular analyses, prepared on permanent slides, in a curated collection.

Amended diagnosis, mitochondrial genome, and phylogenetic position of Sphyranura euryceae (Neodermata, Monogenea, Polystomatidae), a parasite of the Oklahoma salamander

“…We provide the first available mitochondrial genome for Sphyranura and the second only for Polystomatidae. This mitochondrial genome may provide particular value for future phylogenetic work due to the fact that currently available mitogenomes for the sub-class Polyopisthocotylea are all, with the exception of D. hangzhouensis , from the order Mazocraeidea [ 2 ]. Furthermore, a second polystomatid mitogenome allows for the first insights on the gene order rearrangements in Polystomatidae.…”

Morphological and molecular characterization of Encotyllabe vallei Monticelli, 1907 (Monopisthocotylea, Monogenea) from the gilthead seabream Sparus aurata Linnaeus (Teleostei, Sparidae) from the southwestern Mediterranean and notes on host specificity of the genus Encotyllabe Diesing, 1850

“…A tissue sample from the gill of the fish was taken, preserved in absolute ethanol and deposited as a voucher in the SMNH. For the monogenean, a small lateral part of the body above the haptor was separated with a scalpel following previous works on the barcoding of Monogenea (Ayadi et al 2022;Azizi et al 2021;Bouguerche et al 2019aBouguerche et al , 2019bBouguerche et al 2019;Bouguerche et al 2020;Bouguerche et al 2021;Lablack et al 2022) and submitted to molecular analysis, and the rest of the body was mounted on a slide as a voucher for drawing and deposition in a museum collection (Figure 1A). This enables the morphological assessment of sequenced monogeneans.…”