# Complete mitochondrial genome of Echinorhynchus gadi (Acanthocephala, Echinorhynchida) and its phylogenetic implications

## TL;DR

This paper reports the first complete mitochondrial genome of Echinorhynchus gadi, providing insights into its evolution and phylogenetic relationships.

## Contribution

The study presents the first complete mitochondrial genome of the genus Echinorhynchus, filling a critical genomic gap.

## Key findings

- The complete mitochondrial genome of Echinorhynchus gadi is 17,696 bp long and contains 39 genes.
- Phylogenetic analysis places Echinorhynchus gadi and E. truttae in a well-supported monophyletic clade.
- The genome includes tandem repeats and pseudogene fragments, suggesting a tandem duplication and random loss mechanism.

## Abstract

The Echinorhynchidae has a long research history, but its mitochondrial genome evolution remains poorly understood, hindering phylogenetic resolution. In this study, we report the first complete mitochondrial genome of the genus Echinorhynchus, obtained from its type species, Echinorhynchus
gadi. The circular mitogenome was 17,696 bp in length and contained 39 genes: 12 protein-coding genes (lacking atp8), two ribosomal RNA genes, and 25 transfer RNA genes, including two extra copies of trnW and one extra copy of trnV. Five non-coding regions were identified; the major non-coding region contained tandem repeats and pseudogene fragments, consistent with a tandem duplication and random loss mechanism. Phylogenetic analysis based on the concatenated amino acid sequences of the 12 protein-coding genes placed E.
gadi and E.
truttae in a well-supported monophyletic clade representing the genus Echinorhynchus. This clade was sister to Aspersentis
megarhynchus, supporting a close relationship between Echinorhynchidae and Heteracanthocephalidae. Because the published E.
truttae mitogenome is incomplete, this study fills a critical genomic gap and provides a valuable molecular resource for future taxonomic, systematic, and evolutionary studies of Acanthocephala.