Genomic evidence for the polyphyly of the order Sessilia (Crustacea, Cirripedia, Thoracica): tRNAs rearrangement on the mitochondrial genome of hydrothermal vent barnacles

Abstract

Thoracican barnacles had been previously well established the order Pedunculate (goose barnacles) and Sessilia (acorn barnacles) based on the presence or absence of a muscular peduncle in the adult stage. It was recently revealed through phylogenetic analysis with the multilocus sequences that two orders include para- and polyphyletic assemblages. Among phylogenetic issues, it was one of the interesting things that barnacle species from hydrothermal vents formed an independent clade separated from other thoracican barnacles. Mitochondrial (mt) genomes have been known useful for understanding evolutionary history, but only five thoracican species from coastal regions were determined and no vent species have been characterized. For these reasons, we determined the mt genomes of two vent species, the goose barnacle Ashinkailepas kermadecensis and the acorn barnacle Imbricaverruca yamaguchii, and then they were compared with the other thoracicans. The mt genomes of vent species has the identical gene arrangement of thoracicans with protein coding genes (PCGs) and rRNAs. However, their tRNAs were extremely rearranged on the region of control region &#8211 nad2 &#8211 CO1, nad3 &#8211 nad5, and cytB &#8211 nad1 in comparison to the other thoracicans. So vent barnacles have several long intergenic regions from 132 bp to 1290 bp between tRNAs, and the duplicated appearance showed in parts of some intergenic sequences. Foylogenetic analysis with the multilocus sequences that two orders include para- and polyphyletic assemblages. Among phylogenetic issues, it was one of the interesting things that barnacle species from hydrothermal vents formed an independent clade separated from other thoracican barnacles. Mitochondrial (mt) genomes have been known useful for understanding evolutionary history, but only five thoracican species from coastal regions were determined and no vent species have been characterized. For these reasons, we determined the mt genomes of two vent species, the goose barnacle Ashinkailepas kermadecensis and the acorn barnacle Imbricaverruca yamaguchii, and then they were compared with the other thoracicans. The mt genomes of vent species has the identical gene arrangement of thoracicans with protein coding genes (PCGs) and rRNAs. However, their tRNAs were extremely rearranged on the region of control region &#8211 nad2 &#8211 CO1, nad3 &#8211 nad5, and cytB &#8211 nad1 in comparison to the other thoracicans. So vent barnacles have several long intergenic regions from 132 bp to 1290 bp between tRNAs, and the duplicated appearance showed in parts of some intergenic sequences. Fo