Mitogenomics of the suborder Cottoidei (Teleostei: Perciformes): Improved assemblies, mitogenome features, phylogeny, and ecological implications

We determined the mitogenome of Cyclopterus lumpus using a hybrid sequencing approach, and another four closely related species in the Liparidae based on available next-generation sequence data. We found that the mitogenome of C. lumpus was 17,266 bp in length, where the length and organisation were comparable to those reported for cottoids. However, we found a GC-homopolymer region in the intergenic space between tRNA(Leu2) and ND1 in liparids and cyclopterids. Phylogenetic reconstruction confirmed the monophyly of infraorders and firmly supported a sister-group relationship between Cyclopteridae and Liparidae. Purifying selection was the predominant force in the evolution of cottoid mitogenomes. There was significant evidence of relaxed selective pressures along the lineage of deep-sea fish, while selection was intensified in the freshwater lineage. Overall, our analysis provides a necessary expansion in the availability of mitogenomic sequences and sheds light on mitogenomic adaptation in Cottoidei fish inhabiting different aquatic environments.

Automated summary

We determined the mitogenome of Cyclopterus lumpus using a hybrid sequencing approach and studied related species in the Liparidae. The length and organization of C. lumpus mitogenome were similar to those of cottoids. We also found a unique GC-homopolymer region in the intergenic space between tRNA(Leu2) and ND1 in liparids and cyclopterids. Phylogenetic reconstruction confirmed the monophyly of infraorders and supported a sister-group relationship between Cyclopteridae and Liparidae. Overall, our analysis expanded the availability of mitogenomic sequences and shed light on mitogenomic adaptation in Cottoidei fish.