Mitochondrial genome of Chthamalus challengeri (Crustacea: Sessilia): gene order comparison within Chthamalidae and phylogenetic consideration within Balanomorpha

Acorn barnacles are important model species in researches on intertidal ecology, larval development and biofouling. At present, with the development of mitochondrial genomics, it is helpful to understand the phylogenetic relationship from the mitogenomic level. The complete mitochondrial genome of Chthamalus challengeri was presented. The genome is a circular molecule of 15 358 bp. Compared with other species in Balanomorpha, the non-coding region is longer, while the length of the genes is similar to the other species. The overall A+T content of the mitochondrial genome of C. challengeri is 70.5%. There are variations of initiation and stop codons in the known Balanomorpha mitochondrial genomes. The C. challengeri and C. antennatus within the same genus share the identical gene arrangement. However, the gene arrangement of different genera in Chthamalidae is different, as there is a translocation between two tRNA genes and an inversion involving a large gene block. In particular, both srRNA and lrRNA of the two species in Chthamalus are encoded in the heavy strand, differing from the former Balanomorpha species. The topology and gene arrangement in Chthamalidae support each other. Phylogenetic analysis indicates that the Chthamalidae is monophyletic, while the Balanidae and Archaeobalanidae are polyphyletic.