The complete mitochondrial genomes of four cockroaches (Insecta: Blattodea) and phylogenetic analyses within cockroaches

Characterization and Molecular Phylogenetic Analysis of Subfamily Erebinae (Lepidoptera: Noctuoidea: Erebidae) Using Five Complete Mitochondrial Genomes

In this study, the complete mitogenomes of Sympis rufibasis, Lacera noctilio, Oxyodes scrobiculata, Mocis undata, and Artena dotata were newly sequenced to bring up-to-date the database using the next-generation sequencing methods. The gene order of all sequenced mitogenomes was identical consisting of 13 protein-coding genes (PCGs), 22 transfer RNA genes (tRNAs), two ribosomal RNA genes (rRNAs), and a non-coding A+T-rich region, which were common to other Lepidopteran insects. All protein-coding genes (PCGs) initiated with a canonical ATN codon and ended with TAN or an incomplete stop codon, single T. The A+T-rich region of S. rufibasis, L. noctilio, O. scrobiculata, M. undata, and A. dotata are 406 bp, 462 bp, 372 bp, 410 bp, and 406 bp long, respectively, containing number of characteristics that are distinctive to Noctuoidea moths. We analyzed concatenated amino acid sequences of protein-coding genes not including rRNAs, using Maximum Likelihood and Bayesian Inference methods. The phylogenetic analyses indicated that the tribe relationships within Erebinae were reconstructed as (Sypnini+((Erebini 1+Poaphilini 1)+((Euclidiini+Catocalini+(Hypopyrini+Erebini 2))+((Hulodini+(Poaphilini 2+Ophiusini))))). Phylogenetic analyses supported and confirmed the monophyly of the subfamilies' relationships as follows: (Hypeninae+Lymantriinae)+((Scoliopterginae+((Calpinae+Erebinae)+((Herminiinae+Aganainae)+Arctiinae)))) within Erebidae.

Novel Gene Rearrangements in Mitochondrial Genomes of four families of Praying Mantises (Insecta, Mantodea) and Phylogenetic Relationships of Mantodea

The mitochondrial genome (mitogenome) plays an important role in phylogenetic studies of many species. The mitogenomes of many praying mantis groups have been well-studied, but mitogenomes of special mimic praying mantises, especially Acanthopoidea and Galinthiadoidea species, are still sorely lacking in the NCBI database. The present study analyzes five mitogenomes from four species of Acanthopoidea (Angela sp., Callibia diana, Coptopteryx sp., Raptrix fusca) and one of Galinthiadoidea (Galinthias amoena) that were sequenced by the primer-walking method. Among Angela sp. and Coptopteryx sp., three gene rearrangements were detected in ND3-A-R-N-S-E-F and COX1-L2-COX2 gene regions, two of which were novel. In addition, individual tandem repeats were found in control regions of four mitogenomes (Angela sp., C. diana, Coptopteryx sp., G. amoena). For those, plausible explanations were derived from the tandem duplication-random loss (TDRL) model and the slipped-strand mispairing model. One potential motif was found in Acanthopidae that was seen as a synapomorphy. Several conserved block sequences (CBSs) were detected within Acanthopoidea that paved the way for the design of specific primers. Via BI and ML analysis, based on four datasets (PCG12, PCG12R, PCG123, PCG123R), the merged phylogenetic tree within Mantodea was reconstructed. This showed that the monophyly of Acanthopoidea was supported and that the PCG12R dataset was the most suitable for reconstructing the phylogenetic tree within Mantodea.

Characterization of the complete mitochondrial genome of the longhorn beetle, Batocerahorsfieldi (Coleoptera, Cerambycidae) and its phylogenetic analysis with suitable longhorn beetles

Mitochondrial genome analysis is an important tool for studying insect phylogenetics. The longhorn beetle, Batocerahorsfieldi, is a significant pest in timber, economic and protection forests. This study determined the mitochondrial genome of B.horsfieldi and compared it with the mitochondrial genomes of other Cerambycidae with the aim of exploring the phylogenetic status of the pest and the evolutionary relationships among some Cerambycidae subgroups. The complete mitochondrial genome of B.horsfieldi was sequenced by the Illumina HiSeq platform. The mitochondrial genome was aligned and compared with the existing mitochondrial genomes of Batoceralineolata and B.rubus in GenBank (MF521888, MW629558, OM161963, respectively). The secondary structure of transfer RNA (tRNA) was predicted using tRNAScan-SE server v.1.21 and MITOS WebSever. Thirteen protein-coding genes (PCGs) and two ribosomal RNA gene sequences of 21 longhorn beetles, including B.horsfieldi, plus two outgroups, Dryopsernesti (Dryopidae) and Heterocerusparallelus (Heteroceridae), were analyzed. The phylogenetic tree was constructed using maximum likelihood and Bayesian inference methods. In this study, we successfully obtained the complete mitochondrial genome of B.horsfieldi for the first time, which is 15 425 bp in length. It contains 37 genes and an A + T-rich region, arranged in the same order as the recognized ancestor of longhorn beetles. The genome of B.horsfieldi is composed of 33.12% A bases, 41.64% T bases, 12.08% C bases, and 13.16% G bases. The structure, nucleotide composition, and codon usage of the new mitochondrial genome are not significantly different from other longhorn mitochondrial genomes. Phylogenetic analyses revealed that Cerambycidae formed a highly supported single clade, and Vesperidae was either clustered with Cerambycidae or formed a separate clade. Interestingly, B.horsfieldi, B.rubus and B.lineolata were clustered with Monochamus and Anoplophora species in both analyses, with high node support. Additionally, the VesperidaeSpiniphilusspinicornis and Vesperussanzi and the 19 Cerambycidae species formed a sister clade in the Bayesian analysis. Our results have produced new complete mitogenomic data, which will provide information for future phylogenetic and taxonomic research, and provide a foundation for future relevant research.

Evolution of Gene Arrangements in the Mitogenomes of Ensifera and Characterization of the Complete Mitogenome of Schizodactylus jimo

Gene arrangement (relative location of genes) is another evolutionary marker of the mitogenome that can provide extensive information on the evolutionary mechanism. To explore the evolution of gene arrangements in the mitogenome of diversified Ensifera, we sequenced the mitogenome of the unique dune cricket species found in China and used it for phylogenetic analysis, in combination with 84 known Ensiferan mitogenomes. The mitogenome of Schizodactylus jimo is a 16,428-bp circular molecule that contains 37 genes. We identified eight types of gene arrangement in the 85 ensiferan mitogenomes. The gene location changes (i.e., gene translocation and duplication) were in three gene blocks: I-Q-M-ND2, rrnl-rns-V, and ND3-A-R-N-S-E-F. From the phylogenetic tree, we found that Schizodactylus jimo and most other species share a typical and ancient gene arrangement type (Type I), while Grylloidea has two types (Types II and III), and the other five types are rare and scattered in the phylogenetic tree. We deduced that the tandem replication–random loss model is the evolutionary mechanism of gene arrangements in Ensifera. Selection pressure analysis revealed that purifying selection dominated the evolution of the ensiferan mitochondrial genome. This study suggests that most gene rearrangements in the ensiferan mitogenome are rare accidental events.

Novel Mitochondrial Gene Rearrangement and Intergenic Regions Exist in the Mitochondrial Genomes from Four Newly Established Families of Praying Mantises (Insecta: Mantodea)

Simple Summary

Mantodea is regarded as an excellent material to study the gene rearrangements and large non-coding regions (LNCRs) in mitochondrial genomes. Meanwhile, as a result of the convergent evolution and parallelism, the gene rearrangements and LNCRs are specific to some taxonomic groups within Mantodea, which play an important role in phylogenetic relationship research. Nine mitochondrial genomes (mitogenomes) from four newly established families of praying mantises are obtained and annotated. Eight types of gene rearrangements, including four novel types of gene rearrangements in Mantodea, are detected, which can be explained by the tandem replication-random loss (TDRL) model. Moreover, one conserved motif between trnI-trnQ is detected in Toxoderidae. This study shed light on the formation mechanisms of these gene rearrangements and LNCRs in four newly established families of praying mantises.

Abstract

Long non-coding regions (NCRs) and gene rearrangements are commonly seen in mitochondrial genomes of Mantodea and are primarily focused on three regions: CR-I-Q-M-ND2, COX2-K-D-ATP8, and ND3-A-R-N-S-E-F-ND5. In this study, eight complete and one nearly complete mitochondrial genomes of praying mantises were acquired for the purpose of discussing mitochondrial gene rearrangements and phylogenetic relationships within Mantodea, primarily in the newly established families Haaniidae and Gonypetidae. Except for Heterochaeta sp. JZ-2017, novel mitochondrial gene arrangements were detected in Cheddikulama straminea, Sinomiopteryx graham, Pseudovates chlorophaea, Spilomantis occipitalis. Of note is the fact that one type of novel arrangement was detected for the first time in the Cyt b-S2-ND1 region. This could be reliably explained by the tandem replication-random loss (TDRL) model. The long NCR between trnT and trnP was generally found in Iridopteryginae and was similar to the ND4L or ND6 gene. Combined with gene rearrangements and intergenic regions, the monophyly of Haaniidae was supported, whereas the paraphyly of Gonypetidae was recovered. Furthermore, several synapomorphies unique to some clades were detected that conserved block sequences between trnI and trnQ and gaps between trnT and trnP in Toxoderidae and Iridopteryginae, respectively.

Complete mitochondrial genome of Episymploce splendens (Blattodea: Ectobiidae): A large intergenic spacer and lacking of two tRNA genes

The complete mitochondrial genome of Episymploce splendens, 15,802 bp in length, was determined and annotated in this study. The mito-genome included 13 PCGs, 20 tRNAs and 2 rRNAs. Unlike most typical mito-genomes with conservative gene arrangement and exceptional economic organization, E. splendens mito-genome has two tRNAs (tRNA-Gln and tRNA-Met) absence and a long intergenic spacer sequence (93 bp) between tRNA-Val and srRNA, showing the diversified features of insect mito-genomes. This is the first report of the tRNAs deletion in blattarian mito-genomes and we supported the duplication/random loss model as the origin mechanism of the long intergenic spacer. Two Numts, Numt-1 (557 bp) and Numt-2 (975 bp) transferred to the nucleus at about 14.15 Ma to 22.34 Ma, and 19.19 Ma to 24.06 Ma respectively, were found in E. splendens. They can be used as molecular fossils in insect phylogenetic relationship inference. Our study provided useful data for further studies on the evolution of insect mito-genome.

Genome size evaluations in cockroaches: new entries

In this paper, we report genome size (GS) values for nine cockroaches (order Blattodea, families Blattidae, Blaberidae and Ectobiidae, ex Blattelidae), three of which are original additions to the ten already present in the GS database: the death’s head roach (Blaberus craniifer), the Surinam cockroach (Pycnoscelus surinamensis) and the Madeira cockroach (Leucophaea maderae). Regarding the American cockroach (Periplaneta americana), the GS database contains two contrasting values (2.72 vs 3.41 pg); likely, the 2.72 pg value is the correct one as it is strikingly similar to our sperm DNA content evaluation (2.80 ± 0.11 pg). Also, we suggest halving the published GS of the Argentine cockroach Blaptica dubia and the spotted cockroach (the gray cockroach) Nauphoeta cinerea discussing i) the occurrence of a correlation between increasing 2n chromosome number and GS within the order Blattodea; and ii) the possible occurrence of a polyploidization phenomenon doubling a basic GS of 0.58 pg of some termite families (superfamily Blattoidea, epifamily Termitoidae).

Azobenzene-isoxazoline as photopharmacological ligand for optical control of insect GABA receptor and behavior

BACKGROUND

Photopharmacology is a fast-growing photonics-based technology, which realizes the high-resolution regulation of drugs in time and space through light. The purpose of this research was to introduce photochromic groups into the isoxazoline structure to realize the regulation of γ-Aminobutyric acid receptors (GABARs) targeting insect behavior.

RESULTS

Azobenzene-Fluralaner analogs ABF02, ABF03 and ABF04 have been proven to have larvicidal activity against mosquito larvae. Cis-ABF03 had excellent larvicidal activity against mosquito larvae with a median lethal concentration (LC₅₀ ) value of 1.63, which was better than that of trans-ABF03 (LC₅₀  = 3.90). In particular, ABF03 also showed insecticidal activity against Mythimna separata. Further experiments showed that ABF03 (1 μm) induced depolarization of dorsal unpaired median neurons after ultraviolet light irradiation, enhanced affinity to the receptor, and blocked ligand-gated chloride channels of GABARs. ABF03 (1 μm) realized the real-time photoregulation of the behavior of mosquito larvae, which indicated that the synthesized ligand can complete the binding and off-target action of drugs and targets in vivo under the regulation of light.

CONCLUSION

Azobenzene-Isoxazoline as photopharmacological ligand was synthesized and evaluated for optical control of insect GABARs and behavior for the first time. ABF03 completed the differential regulation of cockroach neurons and the real-time reversible regulation of insect behavior. The establishment of photochromic ligands provides a new strategy for basic and convenience-oriented research on GABARs in invertebrates. © 2021 Society of Chemical Industry.

Azobenzene-Semicarbazone Enables Optical Control of Insect Sodium Channels and Behavior

Photopharmacology uses molecular photoswitches to establish control over the action of bioactive molecules. The application of photopharmacology in the research of invertebrate sodium channels has not been investigated. Here we report several photochromic ligands of metaflumizone. One ligand, termed ABM04, underwent reversible trans-cis isomerization under ultraviolet or blue light irradiation. cis-ABM04 had excellent larvicidal activity against mosquito larvae with an LC₅₀ value of 4.39 μM and showed insecticidal activity against Mythimna separata with an LC₅₀ value of 7.19 μM. However, trans-ABM04 was not found to have biological activity. ABM04 (10 μM) can induce depolarization of dorsal unpaired median neurons and enable the real-time photoregulation of mosquito larval behavior. The precise regulation of invertebrate sodium channels is realized for the first time, which provides a new strategy for the basic and accurate research of invertebrate sodium channels.

Comparative Mitogenomes of Two Coreamachilis Species (Microcoryphia: Machilidae) along with Phylogenetic Analyses of Microcoryphia

The order Microcoryphia, commonly known as bristletails, is considered as the most primitive one among living insects. Within this order, two species, Coreamachilis coreanus and C. songi (Machilidae: Machilinae), display the following contrasting reproductive strategies: parthenogenesis occurs in C. coreanus, whereas sexual reproduction is found in C. songi. In the present study, the complete mitogenomes of C. coreanus and C. songi were sequenced to compare their mitogenome structure, analyze relationships within the Microcoryphia, and assess adaptive evolution. The length of the mitogenomes of C. coreanus and C. songi were 15,578 bp and 15,570 bp, respectively, and the gene orders were those of typical insects. A long hairpin structure was found between the ND1 and 16S rRNA genes of both species that seem to be characteristic of Machilinae and Petrobiinae species. Phylogenetic assessment of Coreamachilis was conducted using BI and ML analyses with concatenated nucleotide sequences of the 13 protein-coding genes. The results showed that the monophyly of Machilidae, Machilinae, and Petrobiinae was not supported. The genus Coreamachilis (C. coreanus and C. songi) was a sister clade to Allopsontus helanensis, and then the clade of ((C. coreanus + C. songi) + A. helanensis) was a sister clade to A. baii, which suggests that the monophyly of Allopsontus was not supported. Positive selection analysis of the 13 protein-coding genes failed to reveal any positive selection in C. coreanus or C. songi. The long hairpin structures found in Machilinae and Petrobiinae were highly consistent with the phylogenetic results and could potentially be used as an additional molecular characteristic to further discuss relationships within the Microcoryphia.

Three Complete Mitochondrial Genomes of Orestes guangxiensis, Peruphasma schultei, and Phryganistria guangxiensis (Insecta: Phasmatodea) and Their Phylogeny

Insects of the order Phasmatodea are mainly distributed in the tropics and subtropics and are best known for their remarkable camouflage as plants. In this study, we sequenced three complete mitochondrial genomes from three different families: Orestes guangxiensis, Peruphasma schultei, and Phryganistria guangxiensis. The lengths of the three mitochondrial genomes were 15,896 bp, 16,869 bp, and 17,005 bp, respectively, and the gene composition and structure of the three stick insects were identical to those of the most recent common ancestor of insects. The phylogenetic relationships among stick insects have been chaotic for a long time. In order to discuss the intra- and inter-ordinal relationship of Phasmatodea, we used the 13 protein-coding genes (PCGs) of 85 species for maximum likelihood (ML) and Bayesian inference (BI) analyses. Results showed that the internal topological structure of Phasmatodea had a few differences in both ML and BI trees and long-branch attraction (LBA) appeared between Embioptera and Zoraptera, which led to a non-monophyletic Phasmatodea. Consequently, after removal of the Embioptera and Zoraptera species, we re-performed ML and BI analyses with the remaining 81 species, which showed identical topology except for the position of Tectarchus ovobessus (Phasmatodea). We recovered the monophyly of Phasmatodea and the sister-group relationship between Phasmatodea and Mantophasmatodea. Our analyses also recovered the monophyly of Heteropterygidae and the paraphyly of Diapheromeridae, Phasmatidae, Lonchodidae, Lonchodinae, and Clitumninae. In this study, Peruphasma schultei (Pseudophasmatidae), Phraortes sp. YW-2014 (Lonchodidae), and species of Diapheromeridae clustered into the clade of Phasmatidae. Within Heteropterygidae, O. guangxiensis was the sister clade to O. mouhotii belonging to Dataminae, and the relationship of (Heteropteryginae + (Dataminae + Obriminae)) was recovered.

Insight into the Phylogenetic Relationships among Three Subfamilies within Heptageniidae (Insecta: Ephemeroptera) along with Low-Temperature Selection Pressure Analyses Using Mitogenomes

We determined 15 complete and two nearly complete mitogenomes of Heptageniidae belonging to three subfamilies (Heptageniinae, Rhithrogeninae, and Ecdyonurinae) and six genera (Afronurus, Epeorus, Leucrocuta, Maccaffertium, Stenacron, and Stenonema). Species of Rhithrogeninae and Ecdyonurinae had the same gene rearrangement of CR-I-M-Q-M-ND2, whereas a novel gene rearrangement of CR-I-M-Q-NCR-ND2 was found in Heptageniinae. Non-coding regions (NCRs) of 25-47 bp located between trnA and trnR were observed in all mayflies of Heptageniidae, which may be a synapomorphy for Heptageniidae. Both the BI and ML phylogenetic analyses supported the monophyly of Heptageniidae and its subfamilies (Heptageniinae, Rhithrogeninae, and Ecdyonurinae). The phylogenetic results combined with gene rearrangements and NCR locations confirmed the relationship of the subfamilies as (Heptageniinae + (Rhithrogeninae + Ecdyonurinae)). To assess the effects of low-temperature stress on Heptageniidae species from Ottawa, Canada, we found 27 positive selection sites in eight protein-coding genes (PCGs) using the branch-site model. The selection pressure analyses suggested that mitochondrial PCGs underwent positive selection to meet the energy requirements under low-temperature stress.

The complete mitochondrial genome of Choroterpes (Euthralus) yixingensis (Ephemeroptera: Leptophlebiidae) and its mitochondrial protein-coding gene expression under imidacloprid stress

As one of the most common benthic invertebrates in freshwater, mayflies are very sensitive to changes in water quality and have high requirements for the water environment to allow their nymphs to successfully live and grow. Neonicotinoids, such as imidacloprid, can enter fresh water and pollute the aquatic environment. The present study had two goals: (1) investigate imidacloprid effects on mayfly larvae Choroterpes (Euthralus) yixingensis, and (2) contribute to the phylogenetic status of Ephemeroptera that has always been controversial. Nymphs were collected from Jinhua, China and exposed to different concentrations imidacloprid (5, 10, 20, and 40 μg/L) in the laboratory. Survival of C. yixingensis nymphs decreased as a function of time and imidacloprid concentration with only ~ 55% survival after 72 h exposure to 40 μg/L imidacloprid. After culture under 40 μg/L imidacloprid for 24 h, the steady state transcript levels of mitochondrial COX3, ND4 and ND4L genes were reduced to just 0.07 ± 0.11, 0.30 ± 0.16, and 0.28 ± 0.13 as compared with respective control values (P < 0.01). Steady state transcript levels of ND4 and ND4L were also significantly reduced in a dose-dependent manner (P < 0.05), suggesting that the steady state transcript pattern of these genes in mayfly nymphs can change in response to different levels of environmental contamination. Hence, the mitochondrial protein-coding genes of mayflies could potentially be developed as biomarkers for water ecotoxicity monitoring in the future. In addition, we used the mitochondrial genome sequence of C. yixingensis for an assessment of the phylogenetic tree of Ephemeroptera. The monophyly of Leptophlebiidae was supported and showed that Leptophlebiidae was a sister group to the clade (Baetidae + Caenidae).

Comparative Analysis of Mitogenomes among Five Species of Filchnerella (Orthoptera: Acridoidea: Pamphagidae) and Their Phylogenetic and Taxonomic Implications

Mitogenomes have been widely used for exploring phylogenetic analysis and taxonomic diagnosis. In this study, the complete mitogenomes of five species of Filchnerella were sequenced, annotated and analyzed. Then, combined with other seven mitogenomes of Filchnerella and four of Pamphagidae, the phylogenetic relationships were reconstructed by maximum likelihood (ML) and Bayesian (BI) methods based on PCGs+rRNAs. The sizes of the five complete mitogenomes are Filchnerella sunanensis 15,656 bp, Filchnerella amplivertica 15,657 bp, Filchnerella nigritibia 15,661 bp, Filchnerella pamphagoides 15,661 bp and Filchnerella dingxiensis 15,666 bp. The nucleotide composition of mitogenomes is biased toward A+T. All tRNAs could be folded into the typical clover-leaf structure, except that tRNA Ser (AGN) lacked a dihydrouridine (DHU) arm. The phylogenetic relationships of Filchnerella species based on mitogenome data revealed a general pattern of wing evolution from long wing to increasingly shortened wing.

Increasing 28 mitogenomes of Ephemeroptera, Odonata and Plecoptera support the Chiastomyaria hypothesis with three different outgroup combinations

BACKGROUND

The phylogenetic relationships of Odonata (dragonflies and damselflies) and Ephemeroptera (mayflies) remain unresolved. Different researchers have supported one of three hypotheses (Palaeoptera, Chiastomyaria or Metapterygota) based on data from different morphological characters and molecular markers, sometimes even re-assessing the same transcriptomes or mitochondrial genomes. The appropriate choice of outgroups and more taxon sampling is thought to eliminate artificial phylogenetic relationships and obtain an accurate phylogeny. Hence, in the current study, we sequenced 28 mt genomes from Ephemeroptera, Odonata and Plecoptera to further investigate phylogenetic relationships, the probability of each of the three hypotheses, and to examine mt gene arrangements in these species. We selected three different combinations of outgroups to analyze how outgroup choice affected the phylogenetic relationships of Odonata and Ephemeroptera.

METHODS

Mitochondrial genomes from 28 species of mayflies, dragonflies, damselflies and stoneflies were sequenced. We used Bayesian inference (BI) and Maximum likelihood (ML) analyses for each dataset to reconstruct an accurate phylogeny of these winged insect orders. The effect of outgroup choice was assessed by separate analyses using three outgroups combinations: (a) four bristletails and three silverfish as outgroups, (b) five bristletails and three silverfish as outgroups, or (c) five diplurans as outgroups.

RESULTS

Among these sequenced mitogenomes we found the gene arrangement IMQM in Heptageniidae (Ephemeroptera), and an inverted and translocated tRNA-Ile between the 12S RNA gene and the control region in Ephemerellidae (Ephemeroptera). The IMQM gene arrangement in Heptageniidae (Ephemeroptera) can be explained via the tandem-duplication and random loss model, and the transposition and inversion of tRNA-Ile genes in Ephemerellidae can be explained through the recombination and tandem duplication-random loss (TDRL) model. Our phylogenetic analysis strongly supported the Chiastomyaria hypothesis in three different outgroup combinations in BI analyses. The results also show that suitable outgroups are very important to determining phylogenetic relationships in the rapid evolution of insects especially among Ephemeroptera and Odonata. The mt genome is a suitable marker to investigate the phylogeny of inter-order and inter-family relationships of insects but outgroup choice is very important for deriving these relationships among winged insects. Hence, we must carefully choose the correct outgroup in order to discuss the relationships of Ephemeroptera and Odonata.

Novel tRNA gene rearrangements in the mitochondrial genomes of praying mantises (Mantodea: Mantidae): Translocation, duplication and pseudogenization

Gene rearrangements have been found in several mitochondrial genomes of Mantodea, located in the gene blocks CR-I-Q-M-ND2, COX1-K-D-ATP8 and ND3-A-R-N-S-E-F-ND5. We have sequenced one mitogenome of Amelidae (Yersinia mexicana) and six mitogenomes of Mantidae to discuss the mitochondrial gene rearrangement and the phylogenetic relationship within Mantidae. These mitogenomes showed rearrangements of tRNA genes except for Asiadodis yunnanensis and Hierodula zhangi. These novel gene rearrangements of Mantidae were primarily concentrated in the region of CR-I-Q-M-ND2, including gene translocation, duplication and pseudogenization. For the occurrences of these rearrangements, the tandem duplication-random loss (TDRL) model and slipped-strand mispairing model were suitable to explain. Large non-coding regions (LNCRs) located in the region of CR-I-Q-M-ND2 were detected in most Mantidae species, whereas some LNCRs had high similarity to the control region (CR). Both BI and ML phylogenetic analyses supported the monophyly of Mantidae and the paraphyly of Mantinae. The phylogenetic results with the gene order and the location of NCRs acted as forceful evidence that specific gene rearrangements and special LNCRs may be synapomorphies for several groups of mantises.

Mitogenome Analysis of Four Lamiinae Species (Coleoptera: Cerambycidae) and Gene Expression Responses by Monochamus alternatus When Infected with the Parasitic Nematode, Bursaphelenchus mucronatus

We determined the mitochondrial gene sequence of Monochamus alternatus and three other mitogenomes of Lamiinae (Insect: Coleoptera: Cerambycidae) belonging to three genera (Aulaconotus, Apriona and Paraglenea) to enrich the mitochondrial genome database of Lamiinae and further explore the phylogenetic relationships within the subfamily. Phylogenetic trees of the Lamiinae were built using the Bayesian inference (BI) and maximum likelihood (ML) methods and the monophyly of Monochamus, Anoplophora, and Batocera genera was supported. Anoplophora chinensis, An. glabripennis and Aristobia reticulator were closely related, suggesting they may also be potential vectors for the transmission of the pine wood pathogenic nematode (Bursaphelenchus xylophilus) in addition to M. alternatus, a well-known vector of pine wilt disease. There is a special symbiotic relationship between M. alternatus and Bursaphelenchus xylophilus. As the native sympatric sibling species of B. xylophilus, B. mucronatus also has a specific relationship that is often overlooked. The analysis of mitochondrial gene expression aimed to explore the effect of B. mucronatus on the energy metabolism of the respiratory chain of M. alternatus adults. Using RT-qPCR, we determined and analyzed the expression of eight mitochondrial protein-coding genes (COI, COII, COIII, ND1, ND4, ND5, ATP6, and Cty b) between M. alternatus infected by B. mucronatus and M. alternatus without the nematode. Expression of all the eight mitochondrial genes were up-regulated, particularly the ND4 and ND5 gene, which were up-regulated by 4-5-fold (p < 0.01). Since longicorn beetles have immune responses to nematodes, we believe that their relationship should not be viewed as symbiotic, but classed as parasitic.

Six complete mitochondrial genomes of mayflies from three genera of Ephemerellidae (Insecta: Ephemeroptera) with inversion and translocation of trnI rearrangement and their phylogenetic relationships

As a small order of Pterygota (Insecta), Ephemeroptera has almost 3,500 species around the world. Ephemerellidae is a widely distributed common group of Ephemeroptera. However, the relationship among Ephemerellidae, Vietnamellidae and Teloganellidae is still in dispute. In this study, we sequenced six complete mitogenomes of three genera from Ephemerellidae (Insecta: Ephemeroptera): Ephemerella sp. Yunnan-2018, Serratella zapekinae, Serratella sp. Yunnan-2018, Serratella sp. Liaoning-2019, Torleya grandipennis and T. tumiforceps. These mitogenomes were employed to reveal controversial phylogenetic relationships among the Ephemeroptera, with emphasis on the phylogenetic relationships among Ephemerellidae. The lengths of the six mayfly mitogenomes ranged from 15,134 bp to 15,703 bp. Four mitogenomes of Ephemerella sp. Yunnan-2018, Serratella zapekinae, Serratella sp. Yunnan-2018 and Serratella sp. Liaoning-2019 had 22 tRNAs including an inversion and translocation of trnI. By contrast, the mitogenomes of T. tumiforceps and T. grandipennis had 24 tRNAs due to an extra two copies of inversion and translocation of trnI. Within the family Ephemerellidae, disparate gene rearrangement occurred in the mitogenomes of different genera: one copy of inversion and translocation trnI in the genera Ephemerella and Serratella, and three repeat copies of inversion and translocation of trnI in the genus Torleya. A large non-coding region (≥200 bp) between trnS1 (AGN) and trnE was detected in T. grandipennis and T. tumiforceps. Among the phylogenetic relationship of the Ephemeroptera, the monophyly of almost all families except Siphlonuridae was supported by BI and ML analyses. The phylogenetic results indicated that Ephemerellidae was the sister clade to Vietnamellidae whereas Teloganellidae was not a sister clade of Ephemerellidae and Vietnamellidae.

Comparative analysis of mitogenomes among six species of grasshoppers (Orthoptera: Acridoidea: Catantopidae) and their phylogenetic implications in wing-type evolution

The degree of wing development has a close relationship with insects' movement ability and range, and it should also be closely related to mitochondrial-related genes. The complete mitochondrial genomes of six species of Catantopidae were sequenced, annotated and analyzed. Then, combined with 37 mitogenomes of grasshoppers, the ratio of nonsynonymous substitution to synonymous substitution (Ka/Ks) of the combined sequences of protein coding genes (PCGs) was calculated by DnaSP5, and the phylogenetic relationships were reconstructed by maximum likelihood (ML) and Bayesian (BI) methods based on PCGs+rRNAs. The results showed that the sizes of the six complete mitogenomes are Stenocatantops mistshenkoi Willemse F., 1968, 15,573 bp; Traulia lofaoshana Tinkham, 1940, 15,645 bp; Sinopodisma rostellocerca You, 1980, 15,622 bp; Anapodisma miramae Dovnar-Zapolskij, 1932, 15,189 bp; Qinlingacris elaeodes Yin & Chou, 1979, 15,221 bp; and Eozubovskya planicaudata Zhang & Jin, 1985, 15,830 bp; their structures are the same as those of Acridoidea. The AT bias of the wing-degenerated group (lobiform and apterous) is higher than that of the longipennate group, and more nonsynonymous substitutions accumulated in the wing-degenerated group than in the longipennate group (P = 0.000), which indicates that the wing-degenerated group has undergone weaker evolutionary selection than the longipinnate group. The phylogenetic tree shows that the wing-degenerated group in the Catantopidae are multiorigin and present parallel evolution.

The complete mitochondrial genome of stag beetle Lucanus cervus (Coleoptera: Lucanidae) and phylogenetic analysis

Background

The stag beetle Lucanus cervus (Coleoptera: Lucanidae) is widely distributed in Europe. Habitat loss and fragmentation has led to significant reductions in numbers of this species. In this study, we sequenced the complete mitochondrial genome of L. cervus and reconstructed phylogenetic relationships among Lucanidae using complete mitochondrial genome sequences.

Methods

Raw data sequences were generated by the next generation sequencing using Illumina platform from genomic DNA of L. cervus. The mitochondrial genome was assembled by IDBA and annotated by MITOS. The aligned sequences of mitochondrial genes were partitioned using PartitionFinder 2. Phylogenetic relationships among 19 stag beetle species were constructed using Maximum Likelihood (ML) method implemented in IQ-TREE web server and Bayesian method implemented in PhyloBayes MPI 1.5a. Three scarab beetles were used as outgroups.

Results

The complete mitochondrial genome of L. cervus is 20,109 bp in length, comprising 13 protein-coding genes, 22 transfer RNA genes, two ribosomal RNAs and a control region. The A + T content is 69.93% for the majority strand. All protein-coding genes start with the typical ATN initiation codons except for cox1, which uses AAT. Phylogenetic analyses based on ML and Bayesian methods shown consistent topologies among Lucanidae.

The complete mitochondrial genomes of five longicorn beetles (Coleoptera: Cerambycidae) and phylogenetic relationships within Cerambycidae

Cerambycidae is one of the most diversified groups within Coleoptera and includes nearly 35,000 known species. The relationships at the subfamily level within Cerambycidae have not been convincingly demonstrated and the gene rearrangement of mitochondrial genomes in Cerambycidae remains unclear due to the low numbers of sequenced mitogenomes. In the present study, we determined five complete mitogenomes of Cerambycidae and investigated the phylogenetic relationship among the subfamilies of Cerambycidae based on mitogenomes. The mitogenomic arrangement of all five species was identical to the ancestral Cerambycidae type without gene rearrangement. Remarkably, however, two large intergenic spacers were detected in the mitogenome of Pterolophia sp. ZJY-2019. The origins of these intergenic spacers could be explained by the slipped-strand mispairing and duplication/random loss models. A conserved motif was found between trnS2 and nad1 gene, which was proposed to be a binding site of a transcription termination peptide. Also, tandem repeat units were identified in the A + T-rich region of all five mitogenomes. The monophyly of Lamiinae and Prioninae was strongly supported by both MrBayes and RAxML analyses based on nucleotide datasets, whereas the Cerambycinae and Lepturinae were recovered as non-monophyletic.

A new genus and a new species in the subfamily Polyzosteriinae (Blattodea, Blattidae) from China

Laevifaciesquadrialatagen. et sp. nov. is described from Hainan Province, China based on morphological data. COI data (DNA barcodes) is utilized to confirm the sexual dimorphism occurring in Laevifaciesquadrialatagen. et sp. nov.Melanozosterianitida Brunner von Wattenwyl, 1865, is reported from Guangxi Province, China. A key to the Chinese Polyzosteriinae is provided.

Characteristics of the complete mitochondrial genome of Suhpalacsa longialata (Neuroptera, Ascalaphidae) and its phylogenetic implications

The owlflies (Family Ascalaphidae) belong to the Neuroptera but are often mistaken as dragonflies because of morphological characters. To date, only three mitochondrial genomes of Ascalaphidae, namely Libelloides macaronius; Ascaloptynx appendiculatus; Ascalohybris subjacens, are published in GenBank, meaning that they are greatly under-represented in comparison with the 430 described species reported in this family. In this study, we sequenced and described the complete mitochondrial genome of Suhpalacsa longialata (Neuroptera, Ascalaphidae). The total length of the S. longialata mitogenome was 15,911 bp, which is the longest known to date among the available family members of Ascalaphidae. However, the size of each gene was similar to the other three Ascalaphidae species. The S. longialata mitogenome included a transposition of tRNACys and tRNATrp genes and formed an unusual gene arrangement tRNACys-tRNATrp-tRNATyr (CWY). It is likely that the transposition occurred by a duplication of both genes followed by random loss of partial duplicated genes. The nucleotide composition of the S. longialata mitogenome was as follows: A = 41.0%, T = 33.8%, C = 15.5%, G = 9.7%. Both Bayesian inference and ML analyses strongly supported S. longialata as a sister clade to (Ascalohybris subjacens + L. macaronius), and indicated that Ascalaphidae is not monophyletic.

The complete mitochondrial genome of Vanessa indica and phylogenetic analyses of the family Nymphalidae

Vanessa indica is a small butterfly lacking historical molecular and biological research. Vanessa indica belongs to the family Nymphalidae (Lepidoptera: Papilionoidea), which is the largest group of butterflies and are nearly ubiquitous. However, after more than a century of taxonomic and molecular studies, there is no consensus for family classification, and the phylogenetic relationships within Nymphalidae are controversial. The first objective was to sequence and characterize the complete mitochondrial genome of V. indica. The most important objective was to completely reconstruct the phylogenetic relationships for family members within Nymphalidae. The mitochondrial genomic DNA (mtDNA) of V. indica was extracted and amplified by polymerase chain reaction. The complete mitochondrial sequence was annotated and characterized by analyzing sequences with SeqMan program. The phylogenetic analyses were conducted on thirteen protein coding genes (PCGs) in 95 mtDNA of Nymphalidae downloaded from GenBank for reference using the maximum likelihood method and Bayesian inference to ensure the validity of the results. The complete mitogenome was a circular molecule with 15,191 bp consisting of 13 protein coding genes, two ribosomal RNA genes (16S rRNA and 12S rRNA), 22 transfer RNA (tRNA) genes, and an A + T-rich region (D-loop). The nucleotide composition of the genome was highly biased for A + T content, which accounts for 80.0% of the nucleotides. All the tRNAs have putative secondary structures that are characteristic of mitochondrial tRNAs, except tRNA^Ser(AGN). All the PCGs started with ATN codons, except cytochrome c oxidase subunit 1 (COX1), which was found to start with an unusual CGA codon. Four genes were observed to have unusual codons: COX1 terminated with atypical TT and the other three genes terminated with a single T. The A + T rich region of 327 bp consisted of repetitive sequences, including a ATAGA motif, a 19-bp poly-T stretch, and two microsatellite-like regions (TA)₈. The phylogenetic analyses consistently placed Biblidinae as a sister cluster to Heliconiinae and Calinaginae as a sister clade to Satyrinae. Moreover, the phylogenetic tree identified Libytheinae as a monophyletic group within Nymphalidae. The complete mitogenome of V. indica was 15,191 bp with mitochondrial characterizations common for lepidopteran species, which enriched the mitochondria data of Nymphalid species. And the phylogenetic analysis revealed different classifications and relationships than those previously described. Our results are significant because they would be useful in further understanding of the evolutionary biology of Nymphalidae.

The mitochondrial genome of Caenis sp. (Ephemeroptera: Caenidae) and the phylogeny of Ephemeroptera in Pterygota

The phylogenetic relationship between Ephemeroptera (mayflies) and Odonata (dragonflies and damselflies) remains hotly debated in the insect evolution community. We sequenced the complete mitochondrial genome of Caenis sp. (Ephemeroptera: Caenidae) to discuss the phylogenetic relationship of Palaeoptera. The mitochondrial genome of Caenis sp. is a circular molecule of 15,254 bp in length containing 37 genes (13 protein-coding genes, 22 tRNAs, and 2 rRNAs), which showed the typical insect mitochondrial gene arrangement. In BI and ML phylogenetic trees using 71 species of 12 orders, our results support the Ephemeroptera as the basal group of winged insects.

Two new complete mitochondrial genomes of Dorcus stag beetles (Coleoptera, Lucanidae)

The systematics of Dorcus MacLeay has been a long-standing debate. Mitochondrial genomes were widely used to deeply understand the phylogeny of problematic taxa in virtue of their genetic importance and comprehensiveness. To provide more useful genetic data for resolving the systematic disputation of Dorcus stag beetles. The complete mitochondrial genomes of Dorcus hopei and Dorcus seguyi were obtained using the next generation sequencing. Characteristics of the two genomes are explicated through comparing their genome organization and base composition, protein-coding genes and codon usage, intergenic spacers and non-coding region, transfer and ribosomal RNA genes and control region. Phylogenetic relationships were reconstructed using Maximum likelihood and Bayesian inference analyses based on the concatenated nucleotide sequences of 13 PCGs from 9 stag beetles and 3 scarab beetles. The complete mitogenomes of D. hopei and D. seguyi was 16,026 bp/17,955 bp long, respectively. A tandem repeat with the length of 940 bp was presented in the A+T-rich region in D. hopei. An unexpected non-coding region of 332 bp was located between nad2 and trnW in D. seguyi. The phylogenetic analyses robustly supported that D. hopei formed a branch with the generic type of D. parallelipipedus. Whereas D. seguyi was not covered in the branch of (D. hopei + D. parallelipipedus), but was sister to them. The results indicated that D. hopei should be a good member of Dorcus MacLeay. The taxonomic status of D. seguyi remained to be studied furtherly.

Gene characteristics of the complete mitochondrial genomes of Paratoxodera polyacantha and Toxodera hauseri (Mantodea: Toxoderidae)

The family Toxoderidae (Mantodea) contains an ecologically diverse group of praying mantis species that have in common greatly elongated bodies. In this study, we sequenced and compared the complete mitochondrial genomes of two Toxoderidae species, Paratoxodera polyacantha and Toxodera hauseri, and compared their mitochondrial genome characteristics with another member of the Toxoderidae, Stenotoxodera porioni (KY689118). The lengths of the mitogenomes of T. hauseri and P. polyacantha were 15,616 bp and 15,999 bp, respectively, which is similar to that of S. porioni (15,846 bp). The size of each gene as well as the A+T-rich region and the A+T content of the whole genome were also very similar among the three species as were the protein-coding genes, the A+T content and the codon usages. The mitogenome of T. hauseri had the typical 22 tRNAs, whereas that of P. polyacantha had 26 tRNAs including an extra two copies of trnA-trnR. Intergenic regions of 67 bp and 76 bp were found in T. hauseri and P. polyacantha, respectively, between COX2 and trnK; these can be explained as residues of a tandem duplication/random loss of trnK and trnD. This non-coding region may be synapomorphic for Toxoderidae. In BI and ML analyses, the monophyly of Toxoderidae was supported and P. polyacantha was the sister clade to T. hauseri and S. porioni.

The Complete Mitochondrial Genome of Coptotermes 'suzhouensis' (syn. Coptotermes formosanus) (Isoptera: Rhinotermitidae) and Molecular Phylogeny Analysis

Coptotermes suzhouensis (Isoptera: Rhinotermitidae) is a significant subterranean termite pest of wooden structures and is widely distributed in southeastern China. The complete mitochondrial DNA sequence of C. suzhouensis was analyzed in this study. The mitogenome was a circular molecule of 15,764 bp in length, which contained 13 protein-coding genes (PCGs), 22 transfer RNA genes, two ribosomal RNA genes, and an A+T-rich region with a gene arrangement typical of Isoptera mitogenomes. All PCGs were initiated by ATN codons and terminated by complete termination codons (TAA), except COX2, ND5, and Cytb, which ended with an incomplete termination codon T. All tRNAs displayed a typical clover-leaf structure, except for tRNASer(AGN), which did not contain the stem-loop structure in the DHU arm. The A+T content (69.23%) of the A+T-rich region (949 bp) was higher than that of the entire mitogenome (65.60%), and two different sets of repeat units (A+B) were distributed in this region. Comparison of complete mitogenome sequences with those of Coptotermes formosanus indicated that the two taxa have very high genetic similarity. Forty-one representative termite species were used to construct phylogenetic trees by maximum likelihood, maximum parsimony, and Bayesian inference methods. The phylogenetic analyses also strongly supported (BPP, MLBP, and MPBP = 100%) that all C. suzhouensis and C. formosanus samples gathered into one clade with genetic distances between 0.000 and 0.002. This study provides molecular evidence for a more robust phylogenetic position of C. suzhouensis and inferrs that C. suzhouensis was the synonymy of C. formosanus.

The complete mitochondrial genome of Psychomantis borneensis (Mantodea: Hymenopodidae)

The complete mitochondrial genome of Psychomantis borneensis (Mantodea: Hymenopodidae) was successfully sequenced. The mitochondrial genome is found to be 15,493 bp long and is a circular molecule containing 37 genes (13 protein-coding genes, 22 tRNAs, and 2 rRNAs), typically found in other mantis mitochondrial genomes. The AT content of the whole genome was 72.4% and the length of the control region was 697 bp with 79.9% AT content. A phylogenetic tree was constructed based on the BI and ML analysis of 16 species of Mantodea. The results showed that P. borneensis was a sister clade to (Anaxarcha zhengi + Creobroter gemmata) (Hymenopodidae). The monophyly of the family Mantidae and the genus Theopompa, Hierodula, and Rhombodera were not supported. The outcome of this study will provide a useful data for population genetics studies as well as serve as a tool for better characterizing phylogenetic analysis of Mantodea.

The Complete Mitogenome of the Wood-Feeding Cockroach Cryptocercus meridianus (Blattodea: Cryptocercidae) and Its Phylogenetic Relationship among Cockroach Families

In this study, the complete mitochondrial genome of Cryptocercus meridianus was sequenced. The circular mitochondrial genome is 15,322 bp in size and contains 13 protein-coding genes, two ribosomal RNA genes (12S rRNA and 16S rRNA), 22 transfer RNA genes, and one D-loop region. We compare the mitogenome of C. meridianus with that of C. relictus and C. kyebangensis. The base composition of the whole genome was 45.20%, 9.74%, 16.06%, and 29.00% for A, G, C, and T, respectively; it shows a high AT content (74.2%), similar to the mitogenomes of C. relictus and C. kyebangensis. The protein-coding genes are initiated with typical mitochondrial start codons except for cox1 with TTG. The gene order of the C. meridianus mitogenome differs from the typical insect pattern for the translocation of tRNA-Ser^AGN, while the mitogenomes of the other two Cryptocercus species, C. relictus and C. kyebangensis, are consistent with the typical insect pattern. There are two very long non-coding intergenic regions lying on both sides of the rearranged gene tRNA-Ser^AGN. The phylogenetic relationships were constructed based on the nucleotide sequence of 13 protein-coding genes and two ribosomal RNA genes. The mitogenome of C. meridianus is the first representative of the order Blattodea that demonstrates rearrangement, and it will contribute to the further study of the phylogeny and evolution of the genus Cryptocercus and related taxa.

The complete mitochondrial genome of Damora sagana and phylogenetic analyses of the family Nymphalidae

The monotypic genus Damora (Nymphalidae, Heliconiinae) contains a single species, Damora sagana, which is widely distributed across southern China. Herein, its complete mitogenome was sequenced to further understand lepidopteran mitogenome characteristics, reconstruct the nymphalid family phylogeny, and infer the subdivision of Heliconiinae species. The circular mitogenome was 15,151 bp long, abundant in A and T, and comprised of 13 protein-coding genes (PCGs), 22 transfer RNA (tRNA) genes, 2 ribosomal RNA (rRNA) genes, and one control region with a gene arrangement typical of lepidopteran mitogenomes. ATN codons initiated all PCGs, except cytochrome c oxidase subunit 1 (COX1), which was initiated by a CGA sequence as has been observed in other lepidopterans. Three PCGs (COX1, COX2 and ND4) employed a single T termination signal, whereas others had the typical complete termination codon (TAA). All tRNA genes were folded into the typical cloverleaf structure except for tRNA-Ser (AGN). The A+T-rich region included the conserved motif 'ATAGA' followed by a 17 bp poly-T stretch, which was also observed in tribe Argynnini mitogenomes. A phylogenetic tree was constructed via multiple methods using the 13 PCGs data of D. sagana and other available mitogenomes of nymphalid species. All three phylogenetic trees yielded the same topology. These results were consistent with those from previous studies of most major nymphalid groups, except those regarding tribe subdivision in certain subfamilies such as Argynnini + (Acraeini + Heliconiini) for Heliconiine. Furthermore, our analyses identified that the genus Cethosia was grouped with the genus Acraea composing the tribe Acraeini with strong support.

Mitochondrial genomes of blister beetles (Coleoptera, Meloidae) and two large intergenic spacers in Hycleus genera

BACKGROUND

Insect mitochondrial genomes (mitogenomes) exhibit high diversity in some lineages. The gene rearrangement and large intergenic spacer (IGS) have been reported in several Coleopteran species, although very little is known about mitogenomes of Meloidae.

RESULTS

We determined complete or nearly complete mitogenomes of seven meloid species. The circular genomes encode 13 protein-coding genes (PCGs), 22 transfer RNAs (tRNAs) and two ribosomal RNAs (rRNAs), and contain a control region, with gene arrangement identical to the ancestral type for insects. The evolutionary rates of all PCGs indicate that their evolution is based on purifying selection. The comparison of tRNA secondary structures indicates diverse substitution patterns in Meloidae. Remarkably, all mitogenomes of the three studied Hycleus species contain two large intergenic spacers (IGSs). IGS1 is located between trnW and trnC, including a 9 bp consensus motif. IGS2 is located between trnS2 (UCN) and nad1, containing discontinuous repeats of a pentanucleotide motif and two 18-bp repeat units in both ends. To date, IGS2 is found only in genera Hycleus across all published Coleopteran mitogenomes. The duplication/random loss model and slipped-strand mispairing are proposed as evolutionary mechanisms for the two IGSs (IGS1, IGS2). The phylogenetic analyses using MrBayes, RAxML, and PhyloBayes methods based on nucleotide and amino acid datasets of 13 PCGs from all published mitogenomes of Tenebrionoids, consistently recover the monophylies of Meloidae and Tenebrionidae. Within Meloidae, the genus Lytta clusters with Epicauta rather than with Mylabris. Although data collected thus far could not resolve the phylogenetic relationships within Meloidae, this study will assist in future mapping of the Meloidae phylogeny.

CONCLUSIONS

This study presents mitogenomes of seven meloid beetles. New mitogenomes retain the genomic architecture of the Coleopteran ancestor, but contain two IGSs in the three studied Hycleus species. Comparative analyses of two IGSs suggest that their evolutionary mechanisms are duplication/random loss model and slipped-strand mispairing.

Complete mitochondrial genomes of two blattid cockroaches, Periplaneta australasiae and Neostylopyga rhombifolia, and phylogenetic relationships within the Blattaria

Complete mitochondrial genomes (mitogenomes) of two cockroach species, Periplaneta australasiae and Neostylopyga rhombifolia, 15,605 bp and 15,711 bp in length, respectively, were determined. As reported for other cockroach mitogenomes, the two mitogenomes possessed typical ancestral insect mitogenome gene composition and arrangement. Only several small intergenic spacers were found: one, which was common in all sequenced cockroach mitogenomes except for the genus Cryptocercus, was between tRNA-Ser (UCN) and ND1 and contained a 7bp highly conserved motif (WACTTAA). Three different types of short tandem repeats in the N. rhombifolia control region (CR) were observed. The homologous alignments of these tandem repeats with other six cockroach mitogenome CRs revealed a low similarity. Three conserved sequence blocks (CSB) were detected in both cockroach mitochondrial CRs. CSB1 was specific for blattinine mitogenomes and was highly conserved with 95% similarity, speculating that this block was a possible molecular synapomorphy for this subfamily. CSB3 located nearby downstream of CSB1 and has more variations within blattinine mitogenomes compared with CSB1. The CSB3 was capable of forming stable stem-loop structure with a small T-stretch in the loop portion. We assessed the influence of four datasets and two inference methods on topology within Orthopteroidea. All genes excluding the third codon positions of PCGs could generate more stable topology, and higher posterior probabilities than bootstrap values were presented at some branch nodes. The phylogenetic analysis with different datasets and analytical methods supported the monophyly of Dictyoptera and supported strongly the proposal that Isoptera should be classified as a family (Termitidae) of the Blattaria. Specifically, Shelfordella lateralis was inserted in the clade Periplaneta. Considering the K2P genetic distance, morphological characters, and the phylogenetic trees, we suggested that S. lateralis should be placed in the genus Periplaneta.

The complete mitochondrial genome of the subsocial cockroach Nauphoeta cinerea and phylogenomic analyses of Blattodea mitogenomes suggest reclassification of superfamilies

The genome of the subsocial cockroach Nauphoeta cinerea was partially sequenced in one-twelfth of an Illumina HiSeq lane. The mitochondrial genome was assembled using MIRA software, yielding a circular molecule of 15,923 bp in length and deposited in GenBank under the accession number KY212743. As expected, the mitogenome contained 13 protein-coding genes, 22 transfer tRNAs and 2 ribosomal RNAs. The molecule was assembled using 35,163 sequencing reads of 120 bp each, resulting in ∼286.9× coverage of uniformly distributed reads along the genome. All the 6 complete mitochondrial genomes available for the roaches from the superfamily Blaberoidea were downloaded and compared with the mitogenome of N. cinerea. We also downloaded complete mitochondrial genomes from the superfamily Blattoidea, including 6 mitochondrial genomes of Termitoidae, 2 mitogenomes of Cryptocercoidae and 3 from Blattoidae. A supermatrix dataset presenting the concatenated alignment of all mitochondrial genes was used as input for a maximum likelihood phylogeny. The phylogenomic tree obtained was consistent for most clades, with a relevant exception in the position of the Corydioidea species E. sinensis. Mitochondrial gene information suggests that superfamily Corydioidea should be classified as a clade inside Blattoidea. Nuclear markers and other Corydioidea mitogenomes should be studied to confirm the evolutionary relationships of Blattodea superfamilies.

New Mitogenomes of Two Chinese Stag Beetles (Coleoptera, Lucanidae) and Their Implications for Systematics

Although conspicuous and well-studied, stag beetles have been slow to join the genomic era. In this study, mitochondrial genomes of two stag beetles, Sinodendron yunnanense and Prosopocoilus confucius, are sequenced for the first time. Both of their genomes consisted of 13 protein-coding genes (PCGs), 22 transfer RNA genes (tRNAs), 2 ribosomal RNAs (rRNAs), and a control region. The mitogenome of S. yunnanense was 16,921 bp in length, and P. confucius was 16,951 bp. The location of the gene trnL(UUR), between the A + T-rich and control region in S. yunnanense, is the first observed in Lucanidae. In P. confucius, an unexpected noncoding region of 580 bp was discovered. Maximum likelihood and Bayesian inference on the 13 mitochondrial PCGs were used to infer the phylogenetic relationships among 12 representative stag beetles and three scarab beetles. The topology of the two phylogenetic trees was almost identical: S. yunnanense was recovered as the most basal Lucanid, and the genus Prosopocoilus was polyphyletic due to P. gracilis being recovered sister to the genera Dorcus and Hemisodorcus. The phylogenetic results, genetic distances and mitogenomic characteristics call into question the cohesion of the genus Prosopocoilus. The genetic resources and findings herein attempts to redress understudied systematics and mitogenomics of the stag beetles.

Characterization of complete mitochondrial genome of fives tripe wrasse (Thalassoma quinquevittatum, Lay & Bennett, 1839) and phylogenetic analysis

To further supplement the genome-level features in related species, T. quinquevittatum complete mtDNA was firstly sequenced and de novo assembled by next-generation sequencing. The full-length mtDNA of T. quinquevittatum was a 16,896bp fragment, which was atypical of Labridae, with 2 ribosomal RNA (rRNA) genes, 13 protein-coding genes (PCGs), 23 transfer RNA (tRNA) genes, and a major non-coding control region (D-loop region). Additionally, the mtDNA of T. quinquevittatum exhibited characteristics of A (27.1%), T (29.3%), G (17.8%), and C (25.8%) with a high A+T content (56.4%). Furthermore, the analysis of the average Ka/Ks in the 13 PCGs of three Labridae species indicated a strong purifying selection within this group. Additionally, the phylogenetic analysis based on 13 concatenated PCGs nucleotide and amino acid datasets, showed high value support for the following sister clade among the four genera (T. quinquevittatum, Halichoeres trimaculatus, Halichoeres melanurus, Parajulis poecilepterus). The complete mtDNA of the T. quinquevittatum provided important information for the study in population genetics and evolutionary theory.