| Popis: |
The mackerel icefish (Champsocephalus gunnari Lonnberg, 1905) is a ray-finned fish living in the Southern Ocean around Antarctica. We sequenced the complete mitochondrial (mt) genome of the mackerel icefish and a segment from cytochrome b to the control region (CR) in 32 individuals. The mt genome of the mackerel icefish was rearranged, containing two nicotinamide adenine dinucleotide (reduced form) dehydrogenase subunit 6 (ND6), two tRNAGlu, and two CRs. However, variations in numbers of ND6 and tRNAGlu were observed amongst individuals. These variations included type 1 (containing two ND6 and two tRNAGlu), type 2 (containing one ND6, one incomplete ND6, and one tRNAGlu), and type 3 (containing one ND6 and one tRNAGlu). The gene orders of types 1 and 2, and variations in numbers of ND6 and tRNAGlu were not previously found in any Antarctic notothenioids, whereas type 3 is the same as that of Racovitzia glacialis. Phylogenetic analyses of CR DNA sequences showed that duplicated CRs of the same species formed a monophyletic group, suggesting that duplication of CRs occurred in each species. The frequent duplication of mt genomes in Antarctic notothenioids is an unusual feature in vertebrates. We propose that interspecific hybridization and impairment of mismatch repair might account for the high frequency of gene duplications and rearrangement of mt genomes in Antarctic notothenioids. |
