Mitochondrial genome (mitogenome) is very important to understand molecular evolution and phylogenetics. Herein, in this study, the complete mitogenome of Sesarmops sinensis was reported. The mitogenome was 15,905 bp in size, and contained 13 protein-coding genes (PCGs), two ribosomal RNA (rRNA) genes, 22 transfer RNA (tRNA) genes, and a control region (CR). The AT skew and the GC skew are both negative in the mitogenomes of S. sinensis. The nucleotide composition of the S. sinensis mitogenome was also biased toward A + T nucleotides (75.7%). All tRNA genes displayed a typical mitochondrial tRNA cloverleaf structure, except for the trnS1 gene, which lacked a dihydroxyuridine arm. S. sinensis exhibits a novel rearrangement compared with the Pancrustacean ground pattern and other Brachyura species. Based on the 13 PCGs, the phylogenetic analysis showed that S. sinensis and Sesarma neglectum were clustered on one branch with high nodal support values, indicating that S. sinensis and S. neglectum have a sister group relationship. The group (S. sinensis + S. neglectum) was sister to (Parasesarmops tripectinis + Metopaulias depressus), suggesting that S. sinensis belongs to Grapsoidea, Sesarmidae. Phylogenetic trees based on amino acid sequences and nucleotide sequences of mitochondrial 13 PCGs using BI and ML respectively indicate that section Eubrachyura consists of four groups clearly. The resulting phylogeny supports the establishment of a separate subsection Potamoida. These four groups correspond to four subsections of Raninoida, Heterotremata, Potamoida, and Thoracotremata.

The mitochondrial genome (mitogenome) provides important information for understanding molecular evolution and phylogeny. To determine the systematic status of the family Limacodidae within Lepidoptera, we infer a phylogenetic hypothesis based on the complete mitogenome of Monema flavescens (Lepidoptera: Limacodidae). The mitogenome of M. flavescens is 15,396 base pairs (bp), and includes 13 protein-coding genes (PCGs), two ribosomal RNA (rRNA) genes, 22 transfer RNA (tRNA) genes, and a control region (CR). The AT skew of this mitogenome is slightly negative and the nucleotide composition is also biased towards A + T nucleotides (80.5%). All PCGs are initiated by ATN codons, except for the cytochrome c oxidase subunit 1 (cox1) gene, which is initiated by CGA. All tRNAs display the typical clover-leaf structure characteristic of mitochondrial tRNAs, with the exception of trnS1 (AGN). The mitogenome CR is 401 bp and consists of several features common to Lepidoptera. Phylogenetic analysis using Bayesian Inference (BI) and Maximum Likelihood (ML) based on nucleotide and amino acid sequences of 13 mitochondrial PCGs indicates that M. flavescens belongs to Zygaenoidea. We obtain a well-supported phylogenetic tree consisting of Yponomeutoidea + (Tortricoidea + Zygaenoidea + (Papilionoidea + (Pyraloidea + (Noctuoidea + (Geometroidea + Bombycoidea))))).

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Deciphering the animal mitochondrial genome (mitogenome) is very important to understand their molecular evolution and phylogenetic relationships. In this study, the complete mitogenome of Clistocoeloma sinensis was determined. The mitogenome of C. sinensis was 15,706 bp long, and its A+T content was 75.7%. The A+T skew of the mitogenome of C. sinensis was slightly negative (−0.020). All the transfer RNA genes had the typical cloverleaf structure, except for the trnS1 gene, which lacked a dihydroxyuridine arm. The two ribosomal RNA genes had 80.2% A+T content. The A+T-rich region spanned 684 bp. The gene order within the complete mitogenome of C. sinensis was identical to the pancrustacean ground pattern except for the translocation of trnH. Additionally, the gene order of trnItrnQ-trnM in the pancrustacean ground pattern becomes trnQ-trnI-trnM in C. sinensis. Our phylogenetic analysis showed that C. sinensis and Sesarmops sinensis cluster together with high nodal support values, indicating that C. sinensis and S. sinensis have a sister group relationship. The results support that C. sinensis belongs to Grapsoidea, Sesarmidae. Our findings also indicate that Varunidae and Sesarmidae species share close relationships. Thus, mitogenomes are likely to be valuable tools for systematics in other groups of Crustacea.Mitochondrial DNA (mtDNA) is a typically closed circular molecule approximately ranging in size from 14 to 18 kb. It contains 13 protein-coding genes (PCGs), 2 ribosomal RNA (rRNA) genes, 22 transfer RNA (tRNA) genes, and control region (CR) 1, 2 . mtDNA is characterized by maternal inheritance, simple structure, a small genome size, conserved gene content and organization, high mutation rate, and accelerated rate of nucleotide substitution [3][4][5][6][7] . The mitogenomes of animal mtDNA can provide important information on rearrangement laws and phylogenetic analysis because of their rapid evolutionary rate and lack of genetic recombination 1 . It is becoming increasingly common to use complete animal mitogenomes for phylogenetic reconstruction [8][9][10]

The mitochondrial genome (mitogenome) provides important information for phylogenetic analysis and understanding evolutionary origins. Herein, we sequenced, annotated, and characterised the mitogenome of the crab Helice wuana to better understand its molecular evolution and phylogeny. The 16,359bp mitogenome includes 13 protein-coding genes (PCGs), 22 transfer RNA (tRNA) genes, two ribosomal RNA (rRNA) genes and one control region. The genome composition is highly A+T biased 68.42%, and exhibits a negative AT-skew (-0.036) and GC-skew (-0.269) among Brachyura crabs. Gene rearrangements were detected, as was tandem duplication followed by random loss, which explains the translocation of mitochondrial genes. Phylogenetic analysis showed that H. wuana and H. tientsinensis clustered on one branch with high nodal support values. These results confirm that the placement of H. wuana within the Varunidae family of Thoracotrematan crabs. This study will provided a better understanding for gene rearrangements and crab evolution in the further.

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Mitochondrial genomes (mitogenomes) are important for understanding molecular evolution and phylogenetic relationships. The complete mitogenome of Perisesarma bidens was determined, which is 15,641 bp in length. The A + T content of P. bidens mitogenome was 74.81%. The AT skew was slightly negative (−0.021). The 22 tRNAs ranged from 65 to 73 bp and were highly A + T biased. All tRNA genes had typical cloverleaf structures, except for the trnS1 gene, which lacked a dihydrouridine (DHU) arm. The gene order within the P. bidens mitogenome was identical to the pancrustacean ground pattern, except for the translocation of the trnH. Additionally, the gene order of trnI-trnQ-trnM in pancrustacean ground pattern became trnQ-trnI-trnM in P. bidens. Phylogenetic analyses supported the inclusion of P. bidens in Sesarmidae and the promotion of Sesarminae to Sesarmidae. The results will help us to better understand the status and evolutionary history of Grapsoidea crabs.