Complete mitochondrial genome and the phylogenetic position of the Sphaeroma sp. (Crustacea, Isopod, Sphaeromatidae)

Abstract

The complete mitogenome of Sphaeroma sp. (Crustacea, Isopod, Sphaeromatidae) was determined in this study. The total length of mitogenome was 15,839 bp, and contained 13 protein-coding genes, 21 tRNA genes, 2 rRNA genes, 1 control region, and 2 unknown fragments which longer than 200 bp. The nucleotide composition was 25.80% A, 16.56% C, 25.94% G and 31.67% T. Six initiation codons (ATA, ATC, ATG, ATT, ACG, GTG) and three termination codons (TAA, TAG, TA-) were used in the protein-coding genes. The length of tRNA genes ranged from 52 to 65 bp, and tRNA-Arg was not identified. The phylogenetic result showed Sphaeroma sp. was closely related to Sphaeroma terebrans with high bootstrap value supported.

Long-read sequencing reveals atypical mitochondrial genome structure in a New Zealand marine isopod

“…These sites are commonly asymmetric in species with an ‘atypical’ mitochondrial genome, therefore enabling the expression of both tRNAs [ 18 ]. However, the tRNA-Arg gene is missing in some isopod species with a ‘typical’ mitochondrial genome structure [ 10 , 11 ], while the tRNA-Gly gene is lacking in the Sphaeromatid isopod, Sphaeroma terebrans [ 12 ]. The lack of these specific tRNA loci in some isopods with ‘typical’ mitochondrial genome structures is puzzling because these lineages appear to have lost functionality of at least one tRNA locus.…”

“…This atypical mitochondrial genome is thought to have evolved prior to the divergence of suborders, such as Asellota and Oniscidea [8]. However, this hypothesis is complicated by the presence of 'typical' mitochondrial structures patchily dispersed in suborders such as Sphaeromatidea (family: Sphaeromatidae), Phreatoicidea (family: Amphisopodidae) and Asellota (family: Asellidae) (electronic supplementary material, figure S1) [8][9][10][11][12][13].…”

Long read sequencing reveals atypical mitochondrial genome structure in a New Zealand marine isopod

“…These sites are commonly 'heteroplasmic' in species with an 'atypical' mitochondrial genome, therefore enabling the expression of both tRNAs (Chandler et al, 2015). However, the tRNA-Arg gene is missing in some isopod species with a 'typical' mitochondrial genome structure (Kilpert et al, 2012;Yang, Gao, Hui, et al, 2019), while the tRNA-Gly gene is lacking in the Sphaeromatid isopod, Sphaeroma terebrans (M. Yang, Gao, Yan, et al, 2019). The lack of these specific tRNA loci in some isopods with 'typical' mitochondrial genome structures is puzzling because these lineages appear to have lost functionality of at least one tRNA locus.…”

“…However, this hypothesis is complicated by the presence of 'typical' mitochondrial structure patchily dispersed in suborders such as Sphaeromatidea (family: Sphaeromatidae), Phreatoicidea (family: Amphisopodidae) , and Asellota (family: Asellidae) (Fig. 1) (Doublet et al, 2012;Kilpert et al, 2012;Yang, Gao, Hui, et al, 2019;Yang, Gao, Yan, et al, 2019). A second hypothesis has recently been proposed that relates the dominant occurrence of positive GC skews within Isopoda to the patchy distribution of mitochondrial structures across Isopoda (Baillie, 2020).…”