Abstract
Mud dragons (Kinorhyncha) are an understudied phylum of microscopic marine invertebrates inhabiting a wide range of marine sediments, from shallow coastal habitats to abyssal depths, and occurring from tropical to polar regions. Despite their broad distribution, their minute size often makes them difficult to study. Consequently, molecular resources for the group remain extremely limited and only three complete mitogenomes have been published from this phylum to date. To help fill this substantial gap in genetic data, we sequenced and annotated two new complete mitogenomes from the family Pycnophyidae, Pycnophyes greenlandicus Higgins & Kristensen, 1988 and Cristaphyes cryopygus (Higgins & Kristensen, 1988). Obtained mtDNA sequences were compared with available transcriptomic data from other Kinorhyncha species, providing a more comprehensive basis for the phylogenetic analysis of the phylum. The results showcased unexpected rearrangements in the gene order across all examined taxa, an unusual cox1–tRNA-Glu genes overlap and an unstable phylogenetic position within the Pycnophyidae family. These new sequences not only significantly expand the mitogenomic data available for Kinorhyncha, but also provide an important step toward a better understanding of phylogenetic relationships within the phylum.
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Acknowledgements
The authors are grateful to the staff at the Arctic Station (Disko Island) and the crew of R/V Porsild and R/V Oceania for their help and assistance during the sampling campaigns on Disko Island and Spitsbergen, respectively. We gratefully acknowledge Polish high-performance computing infrastructure PLGrid (HPC Center: ACK Cyfronet AGH) for providing computer facilities and support within computational grant no. PLG/2025/018662 and the Carlsberg Foundation for supporting the fieldwork (grant no. CF20-0122).
Funding
The study was completed thanks to funding provided by the National Science Centre, Poland (grant no. 2022/45/B/NZ8/03545) to KG and the Carlsberg Foundation (grant no. CF20-0122) to MVS. KG was also supported by the Foreign Exchange Office of the Polish Academy of Sciences, which funded her research visit to the Natural History Museum of Denmark. MH is supported by a Ramón y Cajal grant RYC2022/037128-I funded by MICIU/AEI/https://doi.org/10.13039/501100011033 and FSE+.
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Lubośny, M., Zalewska, A., Herranz, M. et al. Towards a mitogenomic phylogeny of mud dragons (Kinorhyncha): two new mitogenomes from the Pycnophyidae family.
Sci Rep (2026). https://doi.org/10.1038/s41598-026-54168-x
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DOI: https://doi.org/10.1038/s41598-026-54168-x
Keywords
- mtDNA
- Lack of stop codon
- Mud dragons
- Phylogenetic
- Pycnophyidae
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