Host-Shift Speciation Proceeded with Gene Flow in Algae Covering Shells.

AbstractHost shifts represent the advancement of a novel niche and often lead to speciation in symbionts. However, its mechanisms are not well understood. Here, we focused on the alga Pseudocladophora conchopheria growing on the shells of intertidal snails. Previous surveys have shown that the alga has host specificity-only attaching to the shell of Lunella correensis-but we discovered that the alga attaches to the shells of multiple sympatric snails. A genome-wide single-nucleotide polymorphism analysis (MIG-seq) was performed to determine whether host-associated speciation occurred in the algae. As a result, there was no gene flow or limited gene flow among the algae from different hosts, and some algae were genetically differentiated among hosts. In addition, the demographic estimate revealed that speciation with gene flow occurred between the algae from different hosts. Therefore, these results support the idea that host-shift speciation gradually proceeded with gene flow in the algae, providing insight into the early evolution of host shifts.

Hydride-ion-conducting K2NiF4-type Ba-Li oxyhydride solid electrolyte.

Hydrogen transport in solids, applied in electrochemical devices such as fuel cells and electrolysis cells, is key to sustainable energy societies. Although using proton (H+) conductors is an attractive choice, practical conductivity at intermediate temperatures (200-400 °C), which would be ideal for most energy and chemical conversion applications, remains a challenge. Alternatively, hydride ions (H-), that is, monovalent anions with high polarizability, can be considered a promising charge carrier that facilitates fast ionic conduction in solids. Here, we report a K2NiF4-type Ba-Li oxyhydride with an appreciable amount of hydrogen vacancies that presents long-range order at room temperature. Increasing the temperature results in the disappearance of the vacancy ordering, triggering a high and essentially temperature-independent H- conductivity of more than 0.01 S cm-1 above 315 °C. Such a remarkable H- conducting nature at intermediate temperatures is anticipated to be important for energy and chemical conversion devices.

First report of the mitogenome of the invasive reef-building polychaete Ficopomatus enigmaticus (Annelida: Serpulidae) and a cryptic lineage from the Japanese Archipelago.

BACKGROUND: The mitochondrial genomes (mitogenomes) of the family Serpulidae are characterized by a high nucleotide sequence divergence and a significant number of gene order rearrangements compared with other families within the phylum Annelida. However, only two of 50 genera of serpulids have mitogenomes already sequenced. In this study, we report the first sequencing and assembly of the complete mitogenome of Ficopomatus, thus providing further knowledge on mitochondrial gene sequences of Serpulidae. METHODS AND RESULTS: A mitogenome of the invasive reef-building polychaete Ficopomatus enigmaticus was amplified by long PCR and sequenced using the Illumina MiSeq System. It comprised 15,853 bp and consisted of 12 protein-coding genes (atp8 was not found), 23 tRNA, and two rRNA genes. The AT and GC skew values were infrequent when compared to annelid mitogenomes but similar to other serpulids sequenced to date (i.e., Spirobranchus and Hydroides). The mitochondrial gene order of F. enigmaticus was highly rearranged compared to other serpulids. To amplify 16S rRNA gene sequences, we developed a 16S rRNA primer set by modifying the universal primer set 16SarL/16SbrH. We detected the 16S rRNA sequence of F. enigmaticus deposited in GenBank erroneously characterized as of serpulid origin. We reported for the first time the presence of two lineages of F. enigmaticus in Japan, which have already been identified in California, Australia, and the Mediterranean. CONCLUSIONS: The first mitochondrial genome of F. enigmaticus showed a unique gene order rearrangement, corroborating the remarkable diversity in the previously reported mitogenomes of other serpulid species. The presence of the two lineages of F. enigmaticus identified for the first time in Japan represents another case of cryptic invasion. The first 16S rRNA gene sequences of F. enigmaticus obtained in the present study can be used as reference sequences in future DNA metabarcoding studies.

Molecular Phylogeny of Thoracotreme Crabs Including Nine Newly Determined Mitochondrial Genomes.

Mitochondrial genomes are used widely for the molecular phylogenetic analysis of animals. Although phylogenetic analyses based on the mitogenomes of brachyurans often yield well-resolved phylogenies, most interfamilial phylogenetic relationships in Thoracotremata remain unclear. We determined nine new mitogenomes of Thoracotremata, including mitogenomes of Camptandriidae (Deiratonotus japonicus), Dotillidae (Ilyoplax integra, Ilyoplax pusilla, and Tmethypocoelis choreutes), Macrophthalmidae (Ilyograpsus nodulosus), Pinnotheridae (Arcotheres sp. and Indopinnixa haematosticta), Plagusiidae (Guinusia dentipes), and Percnidae (Percnon planissimum). Interestingly, Percnon planissimum (Percnidae) was found to possess ≥ 19 repeated sequences in the control region. The gene orders of Il. nodulosus, Arcotheres sp., and In. haematosticta were revealed to be unique among thoracotreme crabs. Although the results of Bayesian and maximum likelihood (ML) phylogenetic analyses of three datasets were incongruent, highly supported clades (PP ≥ 0.99 or BS ≥ 99%) were not contradictory among the analyses. All analyses suggested the paraphyly of Grapsoidea and Ocypodoidea, corroborating the findings of previous studies based on molecular phylogenies of thoracotreme crabs. The phylogenetic positions of symbiotic thoracotreme crabs, Pinnotheridae and Cryptochiridae, were highly supported (Pinnotheridae + Ocypodidae and Cryptochiridae + Grapsidae, respectively) for the Bayesian analyses but not for the ML analyses. Analyses of more thoracotreme species' mitogenome sequences in additional studies will further strengthen the framework for thoracotreme evolution.

Populations of the Intertidal Crab Macrophthalmus banzai are Not Grouped by Latitude: Taiwan Population is Genetically Closer to the Populations in the Japanese Mainland Than the Ryukyu Islands.

Macrophthalmus banzai is an intertidal crab species of Macrophthalmidae inhabiting muddy tidal flats in the northwestern Pacific. A previous study on the population genetic structure of Japanese M. banzai based on the mitochondrial COI gene sequences revealed the presence of two genetically distinguished groups, i.e., the northern group (Honshu, Shikoku, and Kyushu Islands) and the southern group (the Ryukyu Islands). In the present study, we newly determined the COI gene sequences of M. banzai collected from Taiwan and conducted population genetic analyses of these sequences together with Japanese sequences obtained from GenBank to reveal the genetic relationship of this species between Japan and Taiwan. The SAMOVA and pairwise ΦST analysis showed that the Taiwan population is more closely related to the northern group than the southern group. This indicates that the populations of M. banzai are not genetically differentiated by latitude but probably by the pathway of the Kuroshio Current, resulting in the isolation of the population in the Ryukyu Islands. Such a pattern is consistent with the population genetic structure of the fiddler crab Tubuca arcuata shown by a previous study, whereas the pattern differs from those of other intertidal invertebrates. The difference in the larval durations may have influenced the difference in population genetic structures among species. The present study provides a further case of the genetic structure of intertidal species that are not simply regulated by geographic distances.

Molecular and Morphological Assessment of Juvenile and Adult Forms in the Giant Worm Eunice Cf. Aphroditois (Annelida: Eunicidae) and Its Phylogenetic Position in the Family.

Eunice aphroditois (Pallas, 1788) is a large polychaete worm (up to 3 m in length) and the type species of the genus. In Japan, a similar but potentially different species, Eunice cf. aphroditois, is distributed mainly in the rocky shores of the temperate and warm Pacific coasts. Juveniles and adults were suggested to be distinguished by their body color. The juvenile form was previously regarded as distinct species, Eunice flavopicta Izuka, 1912 and Eunice ovalifera Fauvel, 1936, although they are now considered synonymous with E. aphroditois. In this study, we revisited the validity of the present taxonomy based on morphological observations including SEM and microCT, and three molecular markers (cytochrome c oxidase subunit I [COI], 16S rRNA, and histone H3 genes) and investigated the phylogenetic position of E. cf. aphroditois in the family Eunicidae using the combined dataset of three genes (COI + 16S rRNA + 18S rRNA). The adult and juvenile forms were different in body size, color, the distribution of the branchiae and subacicular hooks, and maxillae shape, but not in other characteristics. One individual showed an intermediate body color between the two forms. The adult and juvenile forms shared major haplotypes and the maximum K2P genetic distance of COI was 1.7%, which can be considered within intraspecific variation. In the phylogenetic tree based on the combined gene dataset, E. cf. aphroditois was closely related to Eunice roussaei Quatrefages, 1866 and Eunice cf. violaceomaculata Ehlers, 1887, which are large species from the Mediterranean Sea and the Caribbean Sea, respectively.

Sequential Pressure-Induced B1-B2 Transitions in the Anion-Ordered Oxyhydride Ba2YHO3.

We present a detailed experimental and computational investigation of the influence of pressure on the mixed-anion oxyhydride phase Ba2YHO3, which has recently been shown to support hydride conductivity. The unique feature of this layered perovskite is that the oxide and hydride anions are segregated into distinct regions of the unit cell, in contrast to the disordered arrangement in closely related Ba2ScHO3. Density functional theory (DFT) calculations reveal that the application of pressure drives two sequential B1-B2 transitions in the interlayer regions from rock salt to CsCl-type ordering, one in the hydride-rich layer at approximately 10 GPa and another in the oxide-rich layer at 35-40 GPa. To verify the theoretical predictions, we experimentally observe the structural transition at 10 GPa using high-pressure X-ray diffraction (XRD), but the details of the structure cannot be solved due to peak broadening of the XRD patterns. We use DFT to explore the structural impact of pressure on the atomic scale and show how the pressure-dependent properties can be understood in terms of simple electrostatic engineering.

The complete mitochondrial genome of the sand bubbler crab Scopimera globosa and its phylogenetic position.

The mitochondrial genome has become commonly used for the molecular phylogenetic analysis of animals. Most phylogenetic studies on brachyurans using mitogenome sequences have indicated the paraphyly of superfamilies Grapsoidea and Ocypodoidea but taxon sampling remains limited. The phylogenetic position of Scopimera has been tested in several previous studies using nuclear and/or mitochondrial DNA sequences, but the phylogenetic relationship within the family remains to be resolved. We newly sequenced the complete mitochondrial genome of the sand bubbler crab Scopimera globosa (Ocypodoidea: Dotillidae). Scopimera globosa was clustered with Ilyoplax despite the morphological similarity between Scopimera and Dotilla. The mitochondrial gene order of S. globosa was unique, whereas that of other genera in the family was the same. These results suggest that phylogenetic analysis based on mitogenome sequences and gene order comparison would provide a more robust phylogeny of Dotillidae.

[A Case of Diagnosed Lynch Syndrome in a Patient with Ureteral Cancer].

Lynch syndrome (LS) is an autosomal dominant genetic disorder in which tumors are known to develop at an early age. Upper tract urothelial carcinoma is one of the tumors related to Lynch syndrome. A 49-year-old woman visited a urologic clinic due to left abdominal pain. She had a history of ovarian cancer. Her mother had a history of colorectal cancer and renal pelvic cancer, and her grandmother had had colorectal cancer. After detailed examination, she received laparoscopic left nephroureterectomy and she was pathologically diagnosed with left ureteral cancer. LS was suspected based on her past history, family history, and age. A microsatellite instability (MSI) test gave a positive result, and genetic analysis confirmed a mutation in the MSH2 gene, leading to the diagnosis of Lynch syndrome. Although LS has a high frequency of carcinogenesis, it is thought that an improved prognosis can be achieved by early discovery and treatment of cancer in LS patients. From our case report, we recommend screening of LS in patients with a past/family history, who have had an upper tract urothelial carcinoma. Once LS is diagnosed, the patient should be followed by a planned surveillance of cancer development.

Small-scale population genetic structure of the sand bubbler crab Scopimera ryukyuensis in the Ryukyu Islands, Japan.

Generally, the gene flow of marine organisms is well maintained, but some local populations of coastal species are genetically differentiated even on a small scale (genetic patchiness). Small-scale isolation can be crucial for understanding genetic diversity within a species. The present study examined the population genetic structure of the sand bubbler crab Scopimera ryukyuensis, which is endemic to the Ryukyu Islands in the northwestern Pacific. A total of 52 haplotypes of mitochondrial cytochrome c oxidase subunit I were recovered from 197 specimens collected from four islands. The haplotype and nucleotide diversities were relatively high in the central Ryukyus (Amami-Oshima and Okinawa Islands) with some exceptions but were low at the southern edge of the geographical distribution of the species, i.e., the southern Ryukyus (Ishigaki and Iriomote Islands). Pairwise FST analysis suggested that the gene flow of S. ryukyuensis was largely restricted. The local populations of the species are differentiated among islands, except for stations on Ishigaki Island and a station on Iriomote Island. Moreover, a clear intra-island population genetic structure was observed within Amami-Oshima and Iriomote Islands, e.g., only 20 km between stations. Small-scale isolation among local populations may be a common tendency for coastal species in the Ryukyu Islands, considering the results of previous studies on corals.

High-Pressure Polymorphs of LaHO with Anion Coordination Reversal.

Two novel high-pressure polymorphs of lanthanum oxyhydride have been successfully predicted and stabilized under pressure. When reacted at 3 GPa, the fluorite structure of LaHO with anion-centered tetrahedral (HLa4/OLa4) geometry is transformed to the PbCl2-type structure involving coordination number increase of H- to five (HLa5 square pyramids). Upon further application of pressure to 5 GPa, LaHO changed into the anti Fe2P-type structure. Interestingly, the 5 GPa phase contains tetrahedral HLa4 and square-pyramidal OLa5 geometry, meaning coordination switching, as confirmed by ab initio calculations. The structural analysis shows that this unprecedented phenomenon is enabled by higher compressibility of hydride anion and emphasizes its potential in the search for new high-pressure forms of hydride-based mixed anion materials.

Ba2ScHO3: H- Conductive Layered Oxyhydride with H- Site Selectivity.

Hydride (H-) conduction is a new frontier related to hydrogen transport in solids. Here, a new H- conductive oxyhydride Ba2ScHO3 was successfully synthesized using a high-pressure technique. Powder X-ray and neutron diffraction experiments investigated the fact that Ba2ScHO3 adopts a K2NiF4-type structure with H- ions preferentially occupying the apical sites, as supported by theoretical calculations. Electrochemical impedance spectra showed that Ba2ScHO3 exhibited H- conduction and a conductivity of 5.2 × 10-6 S cm-1 at 300 °C. This value is much higher than that of BaScO2H, which has an ideal perovskite structure, suggesting the advantage of layered structures for H- conduction. Tuning site selectivity of H- ions in layered oxyhydrides might be a promising strategy for designing fast H- conductors applicable for novel electrochemical devices.

Molecular phylogeny of Maldanidae (Annelida): Multiple losses of tube-capping plates and evolutionary shifts in habitat depth.

Inter-familial relationships of the phylum Annelida have been widely studied using molecular phylogenetic/genomic approaches; however, intra-familial relationships remain scarcely investigated in most annelid families. The Maldanidae (bamboo worms) comprise more than 280 species of 40 genera and six subfamilies that occur in various environments from intertidal to hadal zones. Within this family, the taxon Maldanoplaca, which consists of four subfamilies (Maldaninae, Notoproctinae, Nicomachinae, and Euclymeninae), was proposed based on the presence of cephalic and anal plates. Phylogenetic relationships within the family remain largely undetermined based on molecular data. In this study, we reconstructed a molecular phylogeny using 52 maldanid species from six subfamilies based on two nuclear genes (18S rDNA and 28S rDNA) and two mitochondrial genes (16S rDNA and COI). Our analysis confirmed the monophyly of the subfamilies Rhodininae, Maldaninae, Lumbriclymeninae, and Nicomachinae, but neither Maldanoplaca nor the subfamily Euclymeninae were recovered as monophyletic. Nicomachinae was clustered within Euclymeninae. Ancestral state reconstruction suggested that cephalic plates were lost at least three times, despite the functional importance of capping tubes, and that anal plates were lost once. Mapping habitat depth on the phylogenetic tree suggested that habitat shifts among depth zones frequently occurred in distinct maldanid lineages.

Mechanical Properties of Twisted Cellulose Nanofiber-Reinforced Silk Yarns.

Silk has recently attracted considerable interest owing to its versatile properties as a natural fiber, especially in the medical sector. However, the mechanical properties of silk limit its potential applications. In our earlier work, the mechanical performance of silk filaments was enhanced owing to the insertion of cellulose nanofibers (CNFs). Nevertheless, silk filaments must be assembled and twisted to form a continuous yarn. In this study, the mechanical properties of CNF-reinforced silk yarns were evaluated to determine the optimal yarn structure. The evolution of the Young's modulus, ultimate tensile strength, toughness, and elongation at break was assessed as a function of the twist level in comparison with regular silk. The results demonstrated that the most favorable compromise of the mechanical properties was obtained at 1000 twists per meter.

Protocol of efficacy of bifidobacteria intake on gastrointestinal symptoms in symptomatic type 2 diabetes mellitus patients in abdominis: An open-label, randomized controlled trial (Binary STAR study).

BACKGROUND: This randomized, parallel-group study aims to investigate the effects of the probiotic Bifidobacterium bifidum G9-1 (BBG9-1) on the symptoms of diarrhea or constipation in patients with type 2 diabetes mellitus (T2DM). METHODS: This study will examine 100 patients with T2DM who suffering from symptoms of diarrhea or constipation. Eligible patients will be randomly assigned 1:1 to two groups (group A, BBG9-1 group; group B, control group), after the baseline examination. Patients assigned to group A will receive probiotic BBG9-1 oral administration along with their current treatment for 12 weeks, and patients assigned to group B will continue the current treatment for 12 weeks without probiotic BBG9-1 oral administration. Subsequently, examinations similar to the baseline examinations will be performed. The primary endpoint will be a change in the Gastrointestinal Symptom Rating Scale (GSRS) total score from baseline to week 12. Secondary endpoints will include the following: change and percent change in parameters such as GSRS subdomain scores, fecal properties/Bristol stool form scale, defecation frequency, biomarkers, gut microbiota, and macronutrients and factors that affect GSRS total score or constipation/diarrhea subdomain scores from baseline to week 12. DISCUSSION: The results of this study will clarify the utility of probiotic BBG9-1 in the treatment of diarrhea or constipation in patients with T2DM. TRIAL REGISTRATION: jRCTs051220127.

Buried treasure in a public repository: Mining mitochondrial genes of 32 annelid species from sequence reads deposited in the Sequence Read Archive (SRA).

Background: The mitochondrial genomes (mitogenomes) of metazoans generally include the same set of protein-coding genes, which ensures the homology of mitochondrial genes between species. The mitochondrial genes are often used as reference data for species identification based on genetic data (DNA barcoding). The need for such reference data has been increasing due to the application of environmental DNA (eDNA) analysis for environmental assessments. Recently, the number of publicly available sequence reads obtained with next-generation sequencing (NGS) has been increasing in the public database (the NCBI Sequence Read Archive, SRA). Such freely available NGS reads would be promising sources for assembling mitochondrial protein-coding genes (mPCGs) of organisms whose mitochondrial genes are not available in GenBank. The present study aimed to assemble annelid mPCGs from raw data deposited in the SRA. Methods: The recent progress in the classification of Annelida was briefly introduced. In the present study, the mPCGs of 32 annelid species of 19 families in clitellates and allies in Sedentaria (echiurans and polychaetes) were newly assembled from the reads deposited in the SRA. Assembly was performed with a recently published pipeline mitoRNA, which includes cycles of Bowtie2 mapping and Trinity assembly. Assembled mPCGs were deposited in GenBank as Third Party Data (TPA) data. A phylogenetic tree was reconstructed with maximum likelihood (ML) analysis, together with other mPCGs deposited in GenBank. Results and Discussion: mPCG assembly was largely successful except for Travisia forbesii; only four genes were detected from the assembled contigs of the species probably due to the reads targeting its parasite. Most genes were largely successfully obtained, whereas atp8, nad2, and nad4l were only successful in 22-24 species. The high nucleotide substitution rates of these genes might be relevant to the failure in the assembly although nad6, which showed a similarly high substitution rate, was successfully assembled. Although the phylogenetic positions of several lineages were not resolved in the present study, the phylogenetic relationships of some polychaetes and leeches that were not inferred by transcriptomes were well resolved probably due to a more dense taxon sampling than previous phylogenetic analyses based on transcriptomes. Although NGS data are generally better sources for resolving phylogenetic relationships of both higher and lower classifications, there are ensuring needs for specific loci of the mitochondrial genes for analyses that do not require high resolutions, such as DNA barcoding, eDNA, and phylogenetic analysis among lower taxa. Assembly from publicly available NGS reads would help design specific primers for the mitochondrial gene sequences of species, whose mitochondrial genes are hard to amplify by Sanger sequencing using universal primers.

Association between uric acid levels and incidence of type 2 diabetes: Population-based Panasonic cohort study 11.

AIMS: This cohort study intended to assess the association between serum uric acid levels and incidence of type 2 diabetes in a Japanese population. METHODS: Individuals who participated a medical health checkup program carried out by Panasonic Corporation from 2008 to 2018 were included in this study. A total of 122,123 participants (92,718 men and 29,405 women) were included. During the research period, 6,386 participants developed type 2 diabetes. RESULTS: Multivariate analysis showed that, in men, serum uric acid levels were not significantly associated with incident type 2 diabetes after adjusting for diabetes risk factors. However, in women, the risk of type 2 diabetes incidence was higher in the group with uric acid levels 5.1-6.0 mg/dL (hazard ratio, 2.01 [95 % confidence interval: 1.26-3.42]) or > 6.1 mg/dL (hazard ratio, 1.85 [95 % confidence interval: 1.11-3.22]) than in the group with uric acid levels ≤ 3 mg/dL. Furthermore, in women, the area under the receiver operating characteristic curve and optimized cut-off values of uric acid for the incidence of type 2 diabetes at 10 years were 0.720 and 4.8 mg/dL, respectively. CONCLUSIONS: Serum uric acid levels were associated with incident type 2 diabetes in Japanese women but not in Japanese men.

A new family of anti-perovskite oxyhydrides with tetrahedral GaO4 polyanions.

New solid compounds A3-xGaO4H1-y (A = Sr, Ba; x ∼0.15, y ∼0.3), which are the first oxyhydrides containing gallium ions, have been synthesized by high-pressure synthesis. Powder X-ray and neutron diffraction experiments revealed that the series adopts an anti-perovskite structure consisting of hydride-anion-centered HA6 octahedra with tetrahedral GaO4 polyanions, wherein the A- and H-sites show partial defect. Formation energy calculations from the raw materials support that stoichiometric Ba3GaO4H is thermodynamically stable with a wide band gap. Annealing the A = Ba powder under flowing Ar and O2 gas suggests topochemical H- desorption and O2-/H- exchange reactions, respectively.

Effects of Royal Jelly on Gut Dysbiosis and NAFLD in db/db Mice.

Royal jelly (RJ) is a naturally occurring substance synthesized by honeybees and has various health benefits. Herein, we focused on the medium-chain fatty acids (MCFAs) unique to RJ and evaluated their therapeutic efficacy in treating non-alcoholic fatty liver disease (NAFLD). We examined db/m mice that were exclusively fed a normal diet, db/db mice exclusively fed a normal diet, and db/db mice fed varying RJ quantities (0.2, 1, and 5%). RJ improved NAFLD activity scores and decreased gene expression related to fatty acid metabolism, fibrosis, and inflammation in the liver. RJ regulated innate immunity-related inflammatory responses in the small intestine and decreased the expression of genes associated with inflammation and nutrient absorption transporters. RJ increased the number of operational taxonomic units, the abundance of Bacteroides, and seven taxa, including bacteria that produce short-chain fatty acids. RJ increased the concentrations of RJ-related MCFAs (10-hidroxy-2-decenoic acid, 10-hydroxydecanoic acid, 2-decenedioic acid, and sebacic acid) in the serum and liver. These RJ-related MCFAs decreased saturated fatty acid deposition in HepG2 cells and decreased the gene expression associated with fibrosis and fatty acid metabolism. RJ and RJ-related MCFAs improved dysbiosis and regulated the expression of inflammation-, fibrosis-, and nutrient absorption transporter-related genes, thereby preventing NAFLD.

Mitogenome of a stink worm (Annelida: Travisiidae) includes degenerate group II intron that is also found in five congeneric species.

Mitogenomes are useful for inferring phylogenetic relationships between organisms. Although the mitogenomes of Annelida, one of the most morphologically and ecologically diverse metazoan groups have been well sequenced, those of several families remain unexamined. This study determined the first mitogenome from the family Travisiidae (Travisia sanrikuensis), analyzed its mitogenomic features, and reconstructed a phylogeny of Sedentaria. The monophyly of the Terebellida + Arenicolida + Travisiidae clade is supported by molecular phylogenetic analysis. The placement of Travisiidae is unclear because of the lack of mitogenomes from closely related lineages. An unexpected intron appeared within the cox1 gene of T. sanrikuensis and in the same positions of five undescribed Travisia spp. Although the introns are shorter (790-1386 bp) than other group II introns, they can be considered degenerate group II introns due to type II intron maturase open reading frames, found in two of the examined species, and motifs characteristic of group II introns. This is likely the first known case in metazoans where mitochondrial group II introns obtained by a common ancestor are conserved in several descendants. Insufficient evolutionary time for intron loss in Travisiidae, or undetermined mechanisms may have helped maintain the degenerate introns.