Genetic Diversity and Population Structure of Spirobolus bungii as Revealed by Mitochondrial DNA Sequences

Topic: Arthropod Biodiversity: Ecological and Functional Aspects

Invertebrate animals with a segmented body, exoskeleton, and articulated appendages represent the largest phylum in the animal kingdom, Arthropoda, and account for over 80% of all known living species [...].

Characterization of the complete mitochondrial genome of Spirobolus grahami (Diplopoda: Spirobolidae) with phylogenetic analysis

Diplopoda is one of the most diverse and important groups of soil arthropods, but little research has been done on their phylogenetic relationship and evolution. Here, we sequenced and annotated the complete mitochondrial genomes of Spirobolus grahami. The total mitogenome of S. grahami was typical circular, double-stranded molecules, with 14,875 bp in length, including 13 protein-coding genes, 22 tRNAs, two rRNAs, and one control region. Base composition analysis suggested that the mitochondrial sequences were biased toward A and T, with A + T content of 58.68%. The mitogenomes of S. grahami exhibited negative AT and positive GC skews. Most of the 13 PCGs had ATN as the start codon, except COX1 start with CGA, and most PCGs ended with the T stop codon. The dN/dS values for most PCGs were lower than 1, suggesting that purifying selection was likely the main driver of mitochondrial PCG evolution. Phylogenetic analyses based on 13 PCGs using BI and ML methods support the classification of genus Spirobolus and Tropostreptus. Glomeridesmus spelaeus is distantly related to the other Diplopoda species.

The First Complete Mitochondrial Genome of the Genus Litostrophus: Insights into the Rearrangement and Evolution of Mitochondrial Genomes in Diplopoda

This study presents the complete mitochondrial genome (mitogenome) of Litostrophus scaber, which is the first mitogenome of the genus Litostrophus. The mitogenome is a circular molecule with a length of 15,081 bp. The proportion of adenine and thymine (A + T) was 69.25%. The gene ND4L used TGA as the initiation codon, while the other PCGs utilized ATN (A, T, G, C) as the initiation codons. More than half of the PCGs used T as an incomplete termination codon. The transcription direction of the L. scaber mitogenome matched Spirobolus bungii, in contrast to most millipedes. Novel rearrangements were found in the L. scaber mitogenome: trnQ -trnC and trnL1- trnP underwent short-distance translocations and the gene block rrnS-rrnL-ND1 moved to a position between ND4 and ND5, resulting in the formation of a novel gene order. The phylogenetic analysis showed that L. scaber is most closely related to S. bungii, followed by Narceus magnum. These findings enhance our understanding of the rearrangement and evolution of Diplopoda mitogenomes.