The first mitochondrial genome of Capitulum mitella (Crustacea: Cirripedia) from China: revealed the phylogenetic relationship within Thoracica

The Mitochondrial Genome of the Globally Invasive Barnacle Megabalanus coccopoma Darwin 1854 (Crustacea: Balanomorpha): Rearrangement and Phylogenetic Consideration within Balanomorpha

Megabalanus coccopoma (Darwin, 1854) is a globally invasive species in Balanomorpha (Crustacea). This species is a model organism for studying marine pollution and ecology. However, its mitogenome remains unknown. The mitogenome sequencing of M. coccopoma is completed in the present study. It has a 15,098 bp in length, including 13 protein-coding genes (PCGs), 2 ribosomal RNAs (rRNAs), 22 transfer RNAs (tRNAs), along with a putative regulatory area. A substantial A+T bias was observed in the genome composition (68.2%), along with a negative AT (0.82) and GC (−0.136) skew. Compared to the gene sequence of the ground model of pan-crustacea, 13 gene clusters (or genes), such as 10 tRNAs and 3 PCGs, were observed in a different order. This was in line with the previously observed large-scale gene rearrangements of Balanomorpha. Among the 37 genes, the gene cluster (M-nad2-W-cox1-L2-cox2-D-atp8-atp6-cox3-G- nad3-R-N-A-E-S1) Balanomorpha was conserved. Furthermore, phylogeny analysis indicated that the existing Balanomorpha species family was divided into nine rearrangement patterns, supporting the polyphyly of Balanoidea.

The first mitochondrial genome of Balanus trigonus Darwin, 1854 (Sessilia: Balanidae) and molecular phylogeny within Cirripedia

The triangle barnacle Balanus trigonus Darwin, 1854, a cosmopolitan inhabitant of tropical and warm temperate seas, is a member of robust system for the study of evolutionary processes in the intertidal zone. The first mitochondrial genome of B. trigonus is presented. The complete mitochondrial genome of B. trigonus is a circular molecule of 15,560 bp, which encodes 13 protein-coding genes (PCGs), 2 rRNA genes, and 22 tRNA genes. In comparison within Sessilia, the arrangement of the mitochondrial genome of B. trigonus is more similar to Megabalanus spp. than the congener Balanus balanus, which share a same inversion of a large gene block (P-nd4L-nd4-H-nd5-F). Phylogenetic analysis based on mitochondrial PCGs reveals that B. trigonus clusters with Acasta Sulcata (BP = 100), then grouped with Megabalanus volcano and Megabalanus ajax with high support (BP = 90). In further, more data and research are needed to reveal the phylogeny within Cirripedia.

The evolutionary diversity of barnacles, with an updated classification of fossil and living forms

We present a comprehensive revision and synthesis of the higher-level classification of the barnacles (Crustacea: Thecostraca) to the genus level and including both extant and fossils forms. We provide estimates of the number of species in each group. Our classification scheme has been updated based on insights from recent phylogenetic studies and attempts to adjust the higher-level classifications to represent evolutionary lineages better, while documenting the evolutionary diversity of the barnacles. Except where specifically noted, recognized taxa down to family are argued to be monophyletic from molecular analysis and/or morphological data. Our resulting classification divides the Thecostraca into the subclasses Facetotecta, Ascothoracida and Cirripedia. The whole class now contains 14 orders, 65 families and 367 genera. We estimate that barnacles consist of 2116 species. The taxonomy is accompanied by a discussion of major morphological events in barnacle evolution and justifications for the various rearrangements we propose.