Morphology, genetic characterization and mitochondrial genome of Gorgorhynchus fistularius sp. nov. (Acanthocephala, Isthmosacanthidae) from the red cornetfish Fistularia petimba (Lacépède, 1803) (Gasterosteiformes, Fistulariidae), with phylomitogeno

The family Isthmosacanthidae is a group of acanthocephalans mainly parasitic in fishes of Osteichthyes. A new isthmosacanthid species, Gorgorhynchus fistularius sp. nov . (Polymorphida, Isthmosacanthidae) is described based on specimens collected from the red cornetfish Fistularia petimba (Lacépède, 1803) (Syngnathiformes, Fistulariidae) using the integrated morphological characters and molecular data. The complete mitochondrial genome of G. fistularius sp. nov . is presented, which is 14,409 bp in length and represents the first mitogenomic data for the genus Gorgorhynchus and also for the family Isthmosacanthidae. Comparative mitogenomic analysis revealed that the overall A+T content (68.1%) in the mitogenome of G. fistularius sp. nov . is distinctly higher than that of the other mitogenomes of the order Polymorphida reported so far (54.5‒64.4%), but the composition and gene rearrangement of the mitogenome of G. fistularius sp. nov . are identical to the current known mitogenomes of polymorphid species except for Southwellina hispida . Mitogenomic phylogenies supported the Isthmosacanthidae as a distinct family, and suggested new insights into the interfamilial relationships occurring as Plagiorhynchidae + [Isthmosacanthidae + (Centrorhynchidae + Polymorphidae)] in the order Polymorphida.