Complete mitochondrial genomes of Carcinoscorpius rotundicauda and Tachypleus tridentatus (Xiphosura, Arthropoda) and implications for chelicerate phylogenetic studies

The complete mitochondrial genome of a ground beetle Synuchus nitidus (Carabidae: Harpalinae: Sphodrini) from South Korea

The ground beetle Synuchus nitidus (Motschulsky, 1861) (Carabidae: Harpalinae: Sphodrini) is one of the most common species in the forests of South Korea, which has the potential to be utilized as an environmental indicator. Here, we characterized the complete mitochondrial genome (mitogenome) of S. nitidus, which is the first in the harpaline tribe Sphodrini. Its genome is 16,392 bp in length and composed of 13 protein-coding genes (PCGs), 22 tRNA genes, two rRNA genes, and an A + T rich region. In addition, we reconstructed a maximum likelihood tree to elucidate the phylogenetic position of Sphodrini among the seven harpaline tribes using nucleotide sequences of the 13 PCGs. The ML tree supported a monophyletic clade of the subfamily Harpalinae and showed a close relationship between Sphodrini and Lebinii with a low bootstrap value. The complete mitogenome of S. nitidus could be helpful for molecular species identification and exploring phylogenetic relationships among carabids.

Phylogenomics resolves the higher-level phylogeny of herbivorous eriophyoid mites (Acariformes: Eriophyoidea)

BACKGROUND

Eriophyoid mites (Eriophyoidea) are among the largest groups in the Acariformes; they are strictly phytophagous. The higher-level phylogeny of eriophyoid mites, however, remains unresolved due to the limited number of available morphological characters-some of them are homoplastic. Nevertheless, the eriophyoid mites sequenced to date showed highly variable mitochondrial (mt) gene orders, which could potentially be useful for resolving the higher-level phylogenetic relationships.

RESULTS

Here, we sequenced and compared the complete mt genomes of 153 eriophyoid mite species, which showed 54 patterns of rearranged mt gene orders relative to that of the hypothetical ancestor of arthropods. The shared derived mt gene clusters support the monophyly of eriophyoid mites (Eriophyoidea) as a whole and the monophylies of six clades within Eriophyoidea. These monophyletic groups and their relationships were largely supported in the phylogenetic trees inferred from mt genome sequences as well. Our molecular dating results showed that Eriophyoidea originated in the Triassic and diversified in the Cretaceous, coinciding with the diversification of angiosperms.

CONCLUSIONS

This study reveals multiple molecular synapomorphies (i.e. shared derived mt gene clusters) at different levels (i.e. family, subfamily or tribe level) from the complete mt genomes of 153 eriophyoid mite species. We demonstrated the use of derived mt gene clusters in unveiling the higher-level phylogeny of eriophyoid mites, and underlines the origin of these mites and their co-diversification with angiosperms.

Mitochondrial DNA sequence of the horseshoe crab Tachypleus gigas

This paper reports on the complete mitochondrial (mt) genome of a horseshoe crab, Tachypleus gigas (T. gigas), in Kuala Kemaman, Terengganu, Malaysia. Whole-genome sequencing of hemocyte DNA was performed with Illumina HiSeq system and the generated reads were de novo assembled with ABySS 2.1.5 and reassembled using mitoZ against Carcinoscorpius rotundicauda and Limulus polyphemus, resulting in a contig of 15 Kb. Phylogenetic analysis of the assembled mt genome suggests that the Tachypleus gigas is closely related to Tachypleus tridentatus than to Carcinoscorpius rotundicauda.

The complete mitochondrial genome of the two-spotted cricket Gryllus bimaculatus (Orthoptera: Gryllidae) from South Korea

The complete mitochondrial genome of a two-spotted cricket Gryllus bimaculatus (Orthoptera: Gryllidae) from South Korea is determined and characterized in this study. The circular genome is 16,075 bp long, which consists of 13 protein-coding genes (PCGs), 2 ribosomal RNA genes, 22 transfer RNA genes, and an A + T−rich region. It has a base composition of A (40.35%), G (9.09%), C (16.80%), and T (33.76%). The gene order is identical to the ancestral gene arrangement pattern generally shown in arthropods, with the exception of an inversion of trnN-trnS1-trnE into trnE-trnS1-trnN. The maximum likelihood (ML) tree supports that G. bimaculatus is a distinct member of the monophyletic family Gryllidae.

Characterization of the complete mitochondrial genome of Notocotylus sp. (Trematoda, Notocotylidae) and its phylogenetic implications

The parasite genus Notocotylus comprises at least 50 species colonizing mainly aquatic birds and to a lesser extent some mammals, particularly rodents. Here trematode specimens isolated from a wild black swan were characterized and identified to belong to the genus Notocotylus via morphological and molecular analyses. Phylogenetic position of the isolate among other trematodes was determined based on the ribosomal internal transcribed spacer (ITS) 1 and 2. The complete mitochondrial (mt) genome of the isolate was amplified, sequenced, assembled, analyzed, and annotated. The isolate has an AT-rich mt genome (14,317 bp in length) that comprises 12 protein-coding genes (PCGs), 22 transfer RNA genes, and two ribosomal RNA genes. The Notocotylus isolate identified in this study has relatively high mt genome sequence identity and identical gene content and arrangement to a known Notocotylidae species, Ogmocotyle sikae. The isolate formed a genetic clade with O. sikae in phylogenetic analysis of the concatenated PCG amino acid sequences. Compared to the ITS, the trematode mt genome appears more informative for resolving high-level phylogenies. To the best of our knowledge, this is the first study exploring the complete mt genome for the genus Notocotylus, and it offers a novel genomic resource that has important implications for trematode phylogenetics.

The phylogeny and systematics of Xiphosura

Xiphosurans are aquatic chelicerates with a fossil record extending into the Early Ordovician and known from a total of 88 described species, four of which are extant. Known for their apparent morphological conservatism, for which they have gained notoriety as supposed 'living fossils', recent analyses have demonstrated xiphosurans to have an ecologically diverse evolutionary history, with several groups moving into non-marine environments and developing morphologies markedly different from those of the modern species. The combination of their long evolutionary and complex ecological history along with their paradoxical patterns of morphological stasis in some clades and experimentation among others has resulted in Xiphosura being of particular interest for macroevolutionary study. Phylogenetic analyses have shown the current taxonomic framework for Xiphosura-set out in the Treatise of Invertebrate Paleontology in 1955-to be outdated and in need of revision, with several common genera such as Paleolimulus Dunbar, 1923 and Limulitella Størmer, 1952 acting as wastebasket taxa. Here, an expanded xiphosuran phylogeny is presented, comprising 58 xiphosuran species as part of a 158 taxon chelicerate matrix coded for 259 characters. Analysing the matrix under both Bayesian inference and parsimony optimisation criteria retrieves a concordant tree topology that forms the basis of a genus-level systematic revision of xiphosuran taxonomy. The genera Euproops Meek, 1867, Belinurus König, 1820, Paleolimulus, Limulitella, and Limulus are demonstrated to be non-monophyletic and the previously synonymized genera Koenigiella Raymond, 1944 and Prestwichianella Cockerell, 1905 are shown to be valid. In addition, nine new genera (Andersoniella gen. nov., Macrobelinurus gen. nov., and Parabelinurus gen. nov. in Belinurina; Norilimulus gen. nov. in Paleolimulidae; Batracholimulus gen. nov. and Boeotiaspis gen. nov. in Austrolimulidae; and Allolimulus gen. nov., Keuperlimulus gen. nov., and Volanalimulus gen. nov. in Limulidae) are erected to accommodate xiphosuran species not encompassed by existing genera. One new species, Volanalimulus madagascarensis gen. et sp. nov., is also described. Three putative xiphosuran genera-Elleria Raymond, 1944, Archeolimulus Chlupáč, 1963, and Drabovaspis Chlupáč, 1963-are determined to be non-xiphosuran arthropods and as such are removed from Xiphosura. The priority of Belinurus König, 1820 over Bellinurus Pictet, 1846 is also confirmed. This work is critical for facilitating the study of the xiphosuran fossil record and is the first step in resolving longstanding questions regarding the geographic distribution of the modern horseshoe crab species and whether they truly represent 'living fossils'. Understanding the long evolutionary history of Xiphosura is vital for interpreting how the modern species may respond to environmental change and in guiding conservation efforts.

Mitochondrial genome of Amblyomma javanense: a hard tick parasite of the endangered Malayan pangolin (Manis javanica)

Amblyomma javanense is an important ectoparasite of Manis javanica, although the population genetics, molecular biology and systematics of A. javanense remain poorly understood. In the present study, the mitochondrial genome of A. javanense was sequenced using the Illumina HiSeq sequencing platform (Illumina, San Diego, CA, U.S.A.) and compared with the genomes of two closely related species: Amblyomma fimbriatum and Amblyomma americanum. The intraspecies and interspecies relationships of A. javanense and another 21 selected species were investigated by constructing a maximum-likelihood tree and a neighbour-joining tree. The mitochondrial genome of A. javanense was 14 780 bp in length and contained 13 protein-coding genes, 22 transfer RNA genes, two ribosomal RNA genes and two control regions. The results of the comparisons indicate that there is great similarity among these three species, and both trees indicate that A. javanense is a member of the Amblyomminae. The study of A. javanense of pangolins also indicates the premise and foundation of the relationship between the parasite and other species.

The phylogenetic position of eriophyoid mites (superfamily Eriophyoidea) in Acariformes inferred from the sequences of mitochondrial genomes and nuclear small subunit (18S) rRNA gene

Eriophyoid mites (superfamily Eriophyoidea) comprise >4400 species worldwide. Despite over a century of study, the phylogenetic position of these mites within Acariformes is still poorly resolved. Currently, Eriophyoidea is placed in the order Trombidiformes. We inferred the high-level phylogeny of Acari with the mitochondrial (mt) genome sequences of 110 species including four eriophyoid species, and the nuclear small subunit (18S) rRNA gene sequences of 226 species including 25 eriophyoid species. Maximum likelihood (ML), Bayesian inference (BI) and Maximum parsimony (MP) methods were used to analyze the sequence data. Divergence times were estimated for major lineages of Acari using Bayesian approaches. Our analyses consistently recovered the monophyly of Eriophyoidea but rejected the monophyly of Trombidiformes. The eriophyoid mites were grouped with the sarcoptiform mites, or were the sister group of sarcoptiform mites+non-eriophyoid trombidiform mites, depending on data partition strategies. Eriophyoid mites diverged from other mites in the Devonian (384Mya, 95% HPD, 352-410Mya). The origin of eriophyoid mites was dated to the Permian (262Mya, 95% HPD 230-307Mya), mostly prior to the radiation of gymnosperms (Triassic-Jurassic) and angiosperms (early Cretaceous). We propose that the placement of Eriophyoidea in the order Trombidiformes under the current classification system should be reviewed.

Characterization of the complete mitochondrial genome sequence of Homalogaster paloniae (Gastrodiscidae, Trematoda) and comparative analyses with selected digeneans

Gastrodiscidae species are neglected but significant paramphistomes in small ruminants, which can lead to considerable economic losses to the breeding industry of livestock. However, knowledge about molecular ecology, population genetics, and phylogenetic analysis is still limited. In the present study, we firstly sequenced and analyzed the full mitochondrial (mt) genome of Homalogaster paloniae (14,490 bp). The gene contents and organization of the H. paloniae mt genome is the same as that of other digeneans, such as Fasciola hepatica and Paramphistomum cervi. It is interesting that unlike other paramphistomes, H. paloniae is flat in shape which is similar with Fasciola, such as F. hepatica. Phylogenetic analysis of H. paloniae and other 17 selected digeneans using concatenated amino acid sequences of the 12 protein-coding genes showed that Gastrodiscidae is closely related to Paramphistomidae and Gastrothylacidae. The availability of the mt genome sequence of H. paloniae should provide an important foundation for further molecular study of Gastrodiscidae and other digeneans.

The complete mitochondrial genome of a centipede Bothropolys sp. (Chilopoda, Lithobiomorpha, Lithobiidae)

The complete mitochondrial genome of a centipede Bothropolys sp. (Chilopoda, Lithobiomorpha, Lithonidae) is reported here. The mitogenome of Bothropolys sp. is 15,139 bp in total and includes 13 protein-coding genes, 2 ribosomal RNA genes, 22 transfer RNA genes and a putative noncoding region (a possible control region). The pattern of gene order is similar to the arthropod ground pattern, except for the location of trnC.

Mitochondrial genome of Ogmocotyle sikae and implications for phylogenetic studies of the Notocotylidae trematodes

Ogmocotyle spp. (Trematoda: Digenea: Notocotylidae) are neglected but important trematodes that can infect numerous mammal species, causing significant economic losses to livestock industries. However, there have been few studies on the molecular ecology of these trematodes. We amplified and sequenced the complete mitochondrial (mt) genome of Ogmocotyle sikae (14,307 bp). The gene content and gene arrangement of O. sikae mt genome was similar to that of Dicrocoelium chinensis, except that trnE and trnG were reversed. Phylogenetic analysis of O. sikae and selected parasites using Bayesian inference was performed based on concatenated amino acid sequence datasets conceptually translated from the 12 protein-coding genes. The results indicated that the family Notocotylidae is related to the family Paramphistomatidae. Our description of O. sikae mt genome provides a significant resource of molecular markers for future comparative studies of the Notocotylidae and other trematodes.

First mitochondrial genome for the red crab (Charybdis feriata) with implication of phylogenomics and population genetics

In this study, we first described the complete mitochondrial genome for the red crab (Charybdis feriata), elucidated its phylogenetic relationship among 20 species within Decapoda, and estimated the population genetic diversity. The mitochondrial genome was 15,660 bp in size and encoded 13 protein-coding genes, 22 transfer RNA (tRNA) genes, and two ribosomal RNA genes. The gene arrangement of the mitochondrial genome was the same as that of its sister species, C. japonica. Phylogenomic analysis suggested that genus Charybdis should be classified into subfamily Portuninae but not into subfamily Thalamitinae. Moreover, a total of 33 haplotypes of complete cytochrome c oxidase subunit I gene were defined in 70 individuals of C. feriata derived from three localities. Haplotype diversity and nucleotide diversity values among three localities indicated a high level of genetic diversity in C. feriata. AMOVA analysis suggested a low level of genetic differentiation among the three localities (FST = 0.0023, P > 0.05). Neutrality tests and mismatch analysis revealed that C. feriata might have undergone a population expansion event that possibly occurred in the last 61,498 to 43,814 years. This study should be helpful to better understand the evolutionary status, and population genetic diversity of C. feriata and related species.

The complete mitochondrial genome of the orb-weaving spider Neoscona theisi (Walckenaer) (Araneae: Araneidae)

The complete mitochondrial genome of an orb-weaving spider Neoscona theisi (Walckenaer) is determined in this article. It is a typical circular duplex DNA molecule with a length of 14,156 bp, which encodes the same 37 genes as all metazoan mitogenomes and an A + T-rich region (D-loop). The overall A + T content is 75.2% (A: 35.5%; T: 39.8%; G: 15.6%; C: 9.3%). All of the protein-coding genes were initiated by ATN, with the exceptions in three genes. COI has a TTA start codon, COII, COIII and ND6 use TTG as initiation codon. Three genes (ND3, COII and ND5) end with incomplete stop codons (T or TA), while all other genes terminated with canonical stop codons (TAA or TAG). Among 22 transfer RNAs genes, six of them (tRNA^Ala, tRNA^Ser(AGN), tRNA^Ser(UCN), tRNA^Gly, tRNA^Arg and tRNA^His) lack the potential to form the cloverleaf-shaped secondary structure. The A + T-rich region is 559 bp with an A + T content of 79.6%.