The complete mitochondrial genome of a yeti crab Kiwa tyleri Thatje, 2015 (Crustacea: Decapod: Anomura: Kiwaidae) from deep-sea hydrothermal vent

The complete mitochondrial genome of Allogalathea elegans (Adams & White, 1848) (Decapoda: Galatheidae)

The genus Allogalathea belongs to the subfamily Galatheoidea of the family Galatheidae. Here, we report a mitogenome of Allogalathea elegans (Adams & White, 1848). In this study, we obtained the complete mitochondrial genome of Allogalathea elegans by sequencing, which was 16,263 bp in length. The mitogenome contained 37 genes, including the typical set of 13 protein-coding genes (PCGs), 22 transfer RNA (tRNA) genes, and 2 Ribosomal RNA (rRNA) genes. The nucleotides A, C, G, and T distribution was 36.40%, 19.44%, 9.09%, and 35.07%, respectively. The length of the total protein-coding genes was 11,172 bp, which accounts for 68.69% of the whole mitochondrial genome. The phylogenetic result generated by IQ-Tree based on 13 PGCs showed that the infraorder Anomura is monophyletic, and the infraorder Anomura is a sister group of the infraorder Glypheidea. The discovery of the complete mitochondrial genome of A. elegans would help to conduct in-depth research on the infraorder Anomura.

Novel gene rearrangement in the mitochondrial genome of Coenobita brevimanus (Anomura: Coenobitidae) and phylogenetic implications for Anomura

The complete mitochondrial genomes (mitogenomes) can indicate phylogenetic relationships among organisms, as well as useful information about the process of molecular evolution and gene rearrangement mechanisms. However, knowledge on the complete mitogenome of Coenobitidae (Decapoda: Anomura) is quite scarce. Here, we describe in detail the complete mitogenome of Coenobita brevimanus, which is 16,393 bp in length, and contains 13 protein-coding genes, two ribosomal RNA, 22 transfer RNA genes, as well as a putative control region. The genome composition shows a moderate A + T bias (65.0%), and exhibited a negative AT-skew (-0.148) and a positive GC-skew (0.183). Five gene clusters (or genes) involving eleven tRNAs and two PCGs were found to have rearranged with respect to the pancrustacean ground pattern gene order. Duplication-random loss and recombination models were determined as most likely to explain the observed large-scale gene rearrangements. Phylogenetic analysis placed all Coenobitidae species into one clade. The polyphyly of Paguroidea was well supported, whereas the non-monophyly of Galatheoidea was inconsistence with previous findings on Anomura. Taken together, our results help to better understand gene rearrangement process and the evolutionary status of C. brevimanus and lay a foundation for further phylogenetic studies of Anomura.

Large-scale mitochondrial gene rearrangements in the hermit crab Pagurus nigrofascia and phylogenetic analysis of the Anomura

Complete mitochondrial genome (mitogenome) provides important information for better understanding of gene rearrangement, molecular evolution and phylogenetic analysis. Currently, only a few Paguridae mitogenomes have been reported. Herein, we described the complete mitogenome of hermit crab Pagurus nigrofascia. The total length was 15,423 bp, containing 13 protein-coding genes (PCGs), two ribosomal RNA, 22 transfer RNA genes, as well as an AT-rich region. The genome composition was highly A + T biased (71.4%), and exhibited a negative AT-skew (-0.006) and GC-skew (-0.138). Eight tRNA genes, two PCGs and an AT-rich region found to be rearranged with respect to the pancrustacean ground pattern gene order. Duplication-random loss and recombination model were adopted to explain the large-scale gene rearrangement events. Two phylogenetic trees of Anomura involving 12 families were constructed. The results showed that all Paguridae species were clustered into one clade except Pagurus longicarpus, which for the first time imposed raises doubt about the morphological taxonomy of this species. Furthermore, the present study found that higher- level phylogenetic relationships within Anomura were controversial, compared with the previous studies. Our results help to better understand gene rearrangements and the evolutionary status of P. nigrofascia and lay foundation for further phylogenetic study of Anomura.