Mitochondrial DNA Evolution Trends of Baikal Endemic Sponges. I. Mitochondrial Genome of <i>S. khanaevi</i>

The nucleotide sequence of the mitochondrial genome of a new species of sponge from the Baikal endemic family Lubomirskiidae – Swartschewskia khanaevi was determined, the length of which was 26 638 bp. An increase in the rate of accumulation of nucleotide substitutions in protein-coding genes from 2 to 3 times relative to other species of sponges of the Lubomirskiidae family was revealed. On the phylogenetic tree, the species S. khanaevi clusters with another representative of the genus Swartschewskia. It was shown that all studied mitochondrial genomes of Lubomirskiidae are characterized by the presence of a large number and diversity of inverted repeats in intergenic regions, which distinguishes them from other members of the Demospongiae class.