The Mediterranean Mussel Mytilus galloprovincialis (Mollusca: Bivalvia) in Chile: Distribution and Genetic Structure of a Recently Introduced Invasive Marine Species.

The genetic characteristics of invasive species have a significant impact on their ability to establish and spread. The blue mussel (Mytilus galloprovincialis), native to the Mediterranean Sea, is a leading invasive species of intertidal coasts throughout much of the world. Here, we used mitochondrial DNA sequence data to investigate the genetic diversity and phylogeographic structure of invasive (M. galloprovincialis) versus native (Mytilus chilensis) populations of blue mussels in Chile. We evaluated whether genetic diversity in invasive populations could be explained by the genetic characteristics of the native sources from which they might be derived. A phylogenetic analysis confirmed two lineages of the invasive M. galloprovincialis, i.e., the NW Atlantic and the Mediterranean lineages. We found no evidence of genetic structure in the invasive range of M. galloprovincialis in Chile, most probably because of its recent arrival. We did, however, detect a spatial mixture of both M. galloprovincialis lineages at sampling locations along the Chilean coast, giving rise to higher levels of genetic diversity in some areas compared to the population of native M. chilensis. The coastal area of the invasion is still small in extent (~100 km on either side of two large ports), which supports the hypothesis of a recent introduction. Further expansion of the distribution range of M. galloprovincialis may be limited to the north by increasing water temperatures and to the south by a natural biogeographic break that may slow or perhaps stop its spread. The use of internal borders as a tool to minimise or prevent M. galloprovincialis spread is therefore a genuine management option in Chile but needs to be implemented rapidly.

Identifying the source populations supplying a vital economic marine species for the New Zealand aquaculture industry.

Aquaculture of New Zealand's endemic green-lipped mussel (Perna canaliculus) is an industry valued at NZ$ 336 M per annum and is ~ 80% reliant on the natural supply of wild mussel spat harvested at a single location-Te Oneroa-a-Tohe-Ninety Mile Beach (NMB)-in northern New Zealand. Despite the economic and ecological importance of this spat supply, little is known about the population connectivity of green-lipped mussels in this region or the location of the source population(s). In this study, we used a biophysical model to simulate the two-stage dispersal process of P. canaliculus. A combination of backward and forward tracking experiments was used to identify primary settlement areas and putative source populations. The model was then used to estimate the local connectivity, revealing two geographic regions of connectivity in northern New Zealand, with limited larval exchange between them. Although secondary dispersal can double the dispersal distance, our simulations show that spat collected at NMB originate from neighbouring mussel beds, with large contributions from beds located at Ahipara (southern end of NMB). These results provide information that may be used to help monitor and protect these important source populations to ensure the ongoing success of the New Zealand mussel aquaculture industry.

Limited population genetic variation but pronounced seascape genetic structuring in populations of the Mediterranean mussel (Mytilus galloprovincialis) from the eastern Adriatic Sea.

Population genetic analysis of variation at five neutral microsatellite loci for Mediterranean mussels (Mytilus galloprovincialis) from 18 sites along the eastern Adriatic Sea revealed little or no spatial variation. In contrast, seascape genetics analysis revealed a pronounced locus-specific gradient in allelic and genotypic frequencies across the study region. At a sixth locus, MGE7, the frequencies of two alleles, MGE7243 and MGE7249, were strongly associated, negatively and positively, respectively, with a single environmental variable - minimum salinity (minSAL). The frequency of the MGE7243/243 homozygous genotype was strongly negatively associated with minSAL, whereas the frequencies of the MGE7246/249 and the MGE7249/249 genotypes were strongly positively correlated with minSAL. Interpretation of these pronounced gradients is confounded by the fact that minSAL and another environmental variable, maximum sea surface temperature (maxSST), are highly correlated (R = -.911) and are therefore not necessarily acting independently. BLAST searches of the MGE7 locus against M. galloprovincialis whole genome shotgun sequence returned an alignment with contig mg10_S01094 (accession UYJE01010330.1) and 7 predicted M. galloprovincialis proteins VDI82194.1 - VDI82200.1. Conserved domain searches revealed a similar structure to the transcriptional regulator Msx2-interacting protein. The BLASTp search also returned significant alignments to Msx2-interacting proteins in Mytilus coruscus, Crassostrea virginica, and Haliotis rubra. The existence of the MGE7 gradient highlights the role that environmental variation may play in retarding gene flow among wild M. galloprovincialis populations, and also how the success of collection of young mussels (spat) from one site and their transfer to another site (the farm) may be influenced by a single factor such as minSAL or maxSST on a localized scale.

Genetic structure and diversity of the Chilean flat oyster Ostrea chilensis (Bivalvia: Ostreidae) along its natural distribution from natural beds subject to different fishing histories.

Ostrea chilensis (Küster, 1844), the flat oyster, is native to Chile and New Zealand. In Chile, it occurs in a few natural beds, from the northern part of Chiloé Island (41 ºS) to the Guaitecas Archipelago (45 ºS). This bivalve is slow growing, broods its young, and has very limited dispersal potential. The Ostrea chilensis fishery has been over-exploited for a number of decades such that in some locations oysters no longer exist. The aim of this study was to study the genetic diversity of the Chilean flat oyster along its natural distribution to quantify the possible impact of the dredge fishery on wild populations. The genetic structure and diversity of Ostrea chilensis from six natural beds with different histories of fishing activity were estimated. Based on mitochondrial (Cytb) and nuclear (ITS1) DNA sequence variation, our results provide evidence that genetic diversity is different among populations with recent history of wild dredge fishery efforts. We discuss the possible causes of these results. Ultimately, such new information may be used to develop and apply new management measures to promote the sustainable use of this valuable marine resource.

Blue mussels of the Mytilus edulis species complex from South America: The application of species delimitation models to DNA sequence variation.

Smooth-shelled blue mussels, Mytilus spp., have a worldwide antitropical distribution and are ecologically and economically important. Mussels of the Mytilus edulis species complex have been the focus of numerous taxonomic and biogeographical studies, in particular in the Northern hemisphere, but the taxonomic classification of mussels from South America remains unclear. The present study analysed 348 mussels from 20 sites in Argentina, Chile, Uruguay and the Falkland Islands on the Atlantic and Pacific coasts of South America. We sequenced two mitochondrial locus, Cytochrome c Oxidase subunit I (625 bp) and 16S rDNA (443 bp), and one nuclear gene, ribosomal 18S rDNA (1770 bp). Mitochondrial and nuclear loci were analysed separately and in combination using maximum likelihood and Bayesian inference methods to identify the combination of the most informative dataset and model. Species delimitation using five different models (GMYC single, bGMYC, PTP, bPTP and BPP) revealed that the Mytilus edulis complex in South America is represented by three species: native M. chilensis, M. edulis, and introduced Northern Hemisphere M. galloprovincialis. However, all models failed to delimit the putative species Mytilus platensis. In contrast, however, broad spatial scale genetic structure in South America using Geneland software to analyse COI sequence variation revealed a group of native mussels (putatively M. platensis) in central Argentina and the Falkland Islands. We discuss the scope of species delimitation methods and the use of nuclear and mitochondrial genetic data to the recognition of species within the Mytilus edulis complex at regional and global scales.

Combining genotypic and phenotypic variation in a geospatial framework to identify sources of mussels in northern New Zealand.

The New Zealand green-lipped mussel aquaculture industry is largely dependent on the supply of young mussels that wash up on Ninety Mile Beach (so-called Kaitaia spat), which are collected and trucked to aquaculture farms. The locations of source populations of Kaitaia spat are unknown and this lack of knowledge represents a major problem because spat supply may be irregular. We combined genotypic (microsatellite) and phenotypic (shell geochemistry) data in a geospatial framework to determine if this new approach can help identify source populations of mussels collected from two spat-collecting and four non-spat-collecting sites further south. Genetic analyses resolved differentiated clusters (mostly three clusters), but no obvious source populations. Shell geochemistry analyses resolved six differentiated clusters, as did the combined genotypic and phenotypic data. Analyses revealed high levels of spatial and temporal variability in the geochemistry signal. Whilst we have not been able to identify the source site(s) of Kaitaia spat our analyses indicate that geospatial testing using combined genotypic and phenotypic data is a powerful approach. Next steps should employ analyses of single nucleotide polymorphism markers with shell geochemistry and in conjunction with high resolution physical oceanographic modelling to resolve the longstanding question of the origin of Kaitaia spat.

Quantifying and addressing the prevalence and bias of study designs in the environmental and social sciences.

Building trust in science and evidence-based decision-making depends heavily on the credibility of studies and their findings. Researchers employ many different study designs that vary in their risk of bias to evaluate the true effect of interventions or impacts. Here, we empirically quantify, on a large scale, the prevalence of different study designs and the magnitude of bias in their estimates. Randomised designs and controlled observational designs with pre-intervention sampling were used by just 23% of intervention studies in biodiversity conservation, and 36% of intervention studies in social science. We demonstrate, through pairwise within-study comparisons across 49 environmental datasets, that these types of designs usually give less biased estimates than simpler observational designs. We propose a model-based approach to combine study estimates that may suffer from different levels of study design bias, discuss the implications for evidence synthesis, and how to facilitate the use of more credible study designs.

Species-specific genetic variation in response to deep-sea environmental variation amongst Vulnerable Marine Ecosystem indicator taxa.

Understanding the ecological processes that shape spatial genetic patterns of population structure is critical for understanding evolutionary dynamics and defining significant evolutionary and management units in the deep sea. Here, the role of environmental factors (topographic, physico-chemical and biological) in shaping the population genetic structure of four deep-sea habitat-forming species (one sponge - Poecillastra laminaris, three corals - Goniocorella dumosa, Madrepora oculata, Solenosmilia variabilis) was investigated using seascape genetics. Genetic data (nuclear and mitochondrial sequences and microsatellite multilocus genotypes) and environmental variables were employed to build individual-based and population-level models. The results indicated that environmental factors affected genetic variation differently amongst the species, as well as at different geographic scales. For individual-based analyses, different environmental variables explained genetic variation in P. laminaris (dissolved oxygen), G. dumosa (dynamic topography), M. oculata (sea surface temperature and surface water primary productivity), and S. variabilis (tidal current speed). At the population level, factors related to current and food source explained the regional genetic structure in all four species, whilst at the geomorphic features level, factors related to food source and topography were most important. Environmental variation in these parameters may be acting as barriers to gene flow at different scales. This study highlights the utility of seascape genetic studies to better understand the processes shaping the genetic structure of organisms, and to identify environmental factors that can be used to locate sites for the protection of deep-sea Vulnerable Marine Ecosystems.

Cryptic diversity in smooth-shelled mussels on Southern Ocean islands: connectivity, hybridisation and a marine invasion.

BACKGROUND: Large numbers of endemic species inhabit subantarctic continental coasts and islands that are characterised by highly variable environmental conditions. Southern hemisphere populations of taxa that are morphologically similar to northern counterparts have traditionally been considered to be extensions of such Northern hemisphere taxa, and may not exhibit differentiation amongst geographically isolated populations in the Southern Ocean. Smooth-shelled blue mussels of the genus Mytilus that exhibit an anti-tropical distribution are a model group to study phylogeography, speciation and hybridisation in the sea, and contribute to the theory and practice of marine biosecurity. METHODS: We used a single nucleotide polymorphism (SNPs) panel that has the ability to accurately identify reference Northern and Southern hemisphere Mytilus taxa to test for evolutionary differentiation amongst native Southern Ocean island populations. RESULTS: Native mussels from the Falkland Islands and the Kerguelen Islands exhibited greatest affinity to native M. platensis d'Orbigny 1846 from the Atlantic coast of South America. The major Southern Ocean current flow from west to east is likely to explain the spreading of M. platensis to remote offshore islands, as adults via the process of rafting or perhaps directly as larvae. SNPs variation revealed that mussels from Tasmania were native and clearly differentiated from all other blue mussel groups in the Southern and Northern hemispheres. The native mussels M. planulatus from Tasmania and from mainland New Zealand (NZ), and tentatively M. aoteanus from the two NZ Southern Ocean offshore island groups (the Auckland Islands and Campbell Island), formed a distinct M. galloprovincialis-like Southern hemisphere group with closest affinity to Northern hemisphere M. galloprovincialis from the Mediterranean Sea. In all cases, the SNPs revealed evidence of hybridisation between two or more distinct taxa. The invasive Northern hemisphere M. galloprovincialis was identified only in Tasmania, amongst native mussels of a distinct Australian M. planulatus lineage. CONCLUSION: Overall, our results reveal that Southern hemisphere island mussels have mixed genome ancestry and are native, not introduced by human activities. The preservation of distinct evolutionary lineages of Southern hemisphere species needs to be an ongoing focus of conservation efforts, given that population sizes on some of the remote offshore oceanic islands will be small and may be more easily adversely affected by invasion and subsequent hybridisation and introgression than larger populations elsewhere.

The use of spatially explicit genetic variation data from four deep-sea sponges to inform the protection of Vulnerable Marine Ecosystems.

The United Nations General Assembly has called for greater protection of the world's deep-sea species and of features such as Vulnerable Marine Ecosystems (VMEs). Sponges are important components of VMEs and information about their spatially explicit genetic diversity can inform management decisions concerning the placement of protected areas. We employed a spatially explicit hierarchical testing framework to examine genetic variation amongst archived samples of four deep-sea sponges in the New Zealand region. For Poecillastra laminaris Sollas 1886, significant mitochondrial (COI, Cytb) and nuclear DNA (microsatellite) genetic differences were observed between provinces, amongst north-central-south regions and amongst geomorphic features. For Penares sp. no significant structure was detected (COI, 12S) across the same areas. For both Neoaulaxinia persicum Kelly, 2007 (COI, 12S) and Pleroma menoui Lévi & Lévi 1983 (COI) there was no evidence of genetic differentiation within their northern only regional distributions. Of 10 separate species-by-marker tests for isolation-by-distance and isolation-by-depth, only the isolation-by-depth test for N. persicum for COI was significant. The use of archived samples highlights how historical material may be used to support national and international management decisions. The results are discussed in the broader context of existing marine protected areas, and possible future design of spatial management measures for protecting VMEs in the New Zealand region.

Development and characterization of 20 polymorphic microsatellite loci in the deep sea squat lobster, Munida isos Ahyong and Poore, 2004 and cross-amplification in two congeneric species.

Munida isos is a deep sea squat lobster species that is widely distributed across the New Zealand and east Australian region, and is often associated with deep sea vulnerable marine ecosystems. To investigate its population genetic structure and patterns of regional connectivity, microsatellite loci were developed for M. isos from two genomic libraries using the Illumina HiSeq 2500 sequencing platform. Twenty-six loci amplified consistently in M. isos from the Tasman Sea, among which 20 were polymorphic and selectively neutral. Evidence of null alleles was observed at eight loci. Most loci exhibited moderate to high levels of polymorphism, with an average polymorphic information content value of 0.482. The mean number of alleles per locus was 7.45, with a mean expected heterozygosity of 0.520. Thirteen loci exhibited significant deviation from Hardy-Weinberg equilibrium, while only one locus pair was in linkage disequilibrium after false discovery rate correction for multiple testing (P < 0.05). Cross-species amplification tests revealed that the transferability of 14 loci (70%) was positive for the two congeners M. endeavourae and M. gracilis. The accessibility to new polymorphic microsatellite loci will facilitate population genetic studies and aid in developing conservation and management strategies for vulnerable marine ecosystems.

Phylogeography of the threatened tetraploid fish, Schizothorax waltoni, in the Yarlung Tsangpo River on the southern Qinghai-Tibet Plateau: implications for conservation.

The phylogeography of Schizothorax waltoni, an endemic and endangered tetraploid schizothoracine fish in the Yarlung Tsangpo River (YLTR) on southern margin of Qinghai-Tibet Plateau (QTP), was investigated using two mitochondrial DNA regions and eleven microsatellite loci. Analyses of concatenated sequences of cytochrome b (1141 bp) and the control region (712 bp) revealed high haplotype diversity and moderate nucleotide diversity. High genetic diversity was observed based on microsatellite variation. Both mtDNA and microsatellite analyses revealed significant genetic differentiation between the eastern population (Mainling) and the other four populations to the west, and non-significant genetic differentiation amongst the three central populations in the west. Significant genetic differentiation was observed between the western population (Shigatse) and the three central populations based on microsatellite analyses alone. Bayesian skyline plot analyses showed that S. waltoni experienced a pronounced population expansion 0.05 to 0.10 Ma. Hierarchical structure analyses of microsatellite data indicated that S. waltoni could be split into three groups (western, central and eastern YLTR). The results indicate that three management units should be considered for S. waltoni. Our findings highlight the need for the conservation and effective management of S. waltoni, which is a key member of the endemic and highly threatened fishes of the QTP.

Population genetic structure and connectivity of deep-sea stony corals (Order Scleractinia) in the New Zealand region: Implications for the conservation and management of vulnerable marine ecosystems.

Deep-sea stony corals, which can be fragile, long-lived, late to mature and habitat-forming, are defined as vulnerable marine ecosystem indicator taxa. Under United Nations resolutions, these corals require protection from human disturbance such as fishing. To better understand the vulnerability of stony corals (Goniocorella dumosa, Madrepora oculata, Solenosmilia variabilis) to disturbance within the New Zealand region and to guide marine protected area design, genetic structure and connectivity were determined using microsatellite loci and DNA sequencing. Analyses compared population genetic differentiation between two biogeographic provinces, amongst three subregions (north-central-south) and amongst geomorphic features. Extensive population genetic differentiation was revealed by microsatellite variation, whilst DNA sequencing revealed very little differentiation. For G. dumosa, genetic differentiation existed amongst regions and geomorphic features, but not between provinces. For M. oculata, only a north-central-south regional structure was observed. For S. variabilis, genetic differentiation was observed between provinces, amongst regions and amongst geomorphic features. Populations on the Kermadec Ridge were genetically different from Chatham Rise populations for all three species. A significant isolation-by-depth pattern was observed for both marker types in G. dumosa and also in ITS of M. oculata. An isolation-by-distance pattern was revealed for microsatellite variation in S. variabilis. Medium to high levels of self-recruitment were detected in all geomorphic populations, and rates and routes of genetic connectivity were species-specific. These patterns of population genetic structure and connectivity at a range of spatial scales indicate that flexible spatial management approaches are required for the conservation of deep-sea corals around New Zealand.

First evidence of establishment of the rayed pearl oyster, Pinctada imbricata radiata (Leach, 1814), in the eastern Adriatic Sea.

The Mediterranean Sea is increasingly under threat from invasive species that may negatively affect biodiversity and/or modify ecosystem structure and function. The bivalve mollusc Pinctada imbricata radiata is listed among the 100 most invasive species in the Mediterranean. A first finding of an established population of P. imbricata radiata in the coastal waters of the eastern Adriatic Sea, is presented in this paper. Six and then 30 live specimens were collected in 2015 and in 2017, respectively, at depths of 5 to 15m from the island of Mljet, Croatia. DNA sequencing of the mitochondrial cytochrome c oxidase I gene (COI) revealed three different haplotypes. All samples showed greatest similarity (98 to >99%) to P. radiata COI sequence records in GenBank (=P. imbricata radiata as used in this paper). A Neighbour Joining tree placed all Croatian samples within the 100% bootstrap supported clade for P. imbricata radiata.

Phylogeography and population genetics of Schizothorax o'connori: strong subdivision in the Yarlung Tsangpo River inferred from mtDNA and microsatellite markers.

The Qinghai-Tibet Plateau (QTP) is a biodiversity hotspot, resulting from its geological history, contemporary environment and isolation. Uplift of the QTP and Quaternary climatic oscillations are hypothesised to have influenced the genetic diversity, population structure and dynamics of all QTP endemic species. In this study, we tested this hypothesis by assaying variation at two mitochondrial DNA regions (cytochrome b and control region) and at 12 microsatellite loci of seven populations of the endemic fish, Schizothorax o'connori from the Yarlung Tsangpo River (YLTR) on the QTP. Analyses revealed one group of six populations to the west, above the Yarlung Tsangpo Grand Canyon (YTGC), and a second group to the east below the YTGC. Estimates of the timing of this east-west split indicate that these groups represent evolutionarily significant units that have evolved separately and rapidly in the middle Pleistocene, at the time of the Kunlun-Huanghe Movement A Phase and the Naynayxungla glaciation. Population dynamic analyses indicate that S. o'connori experienced a pronounced late Pleistocene expansion during the last interglacial period. The results of this study support the hypotheses that the QTP uplift and Quaternary climatic oscillations have played important roles in shaping the population genetics and dynamics of this endemic fish.

Invasive blue mussels threaten regional scale genetic diversity in mainland and remote offshore locations: the need for baseline data and enhanced protection in the Southern Ocean.

Human-mediated biological transfers of species have substantially modified many ecosystems with profound environmental and economic consequences. However, in many cases, invasion events are very hard to identify because of the absence of an appropriate baseline of information for receiving sites/regions. In this study, use of high-resolution genetic markers (single nucleotide polymorphisms - SNPs) highlights the threat of introduced Northern Hemisphere blue mussels (Mytilus galloprovincialis) at a regional scale to Southern Hemisphere lineages of blue mussels via hybridization and introgression. Analysis of a multispecies SNP dataset reveals hotspots of invasive Northern Hemisphere blue mussels in some mainland New Zealand locations, as well as the existence of unique native lineages of blue mussels on remote oceanic islands in the Southern Ocean that are now threatened by invasive mussels. Samples collected from an oil rig that has moved between South Africa, Australia, and New Zealand were identified as invasive Northern Hemisphere mussels, revealing the relative ease with which such non-native species may be moved from region to region. In combination, our results highlight the existence of unique lineages of mussels (and by extension, presumably of other taxa) on remote offshore islands in the Southern Ocean, the need for more baseline data to help identify bioinvasion events, the ongoing threat of hybridization and introgression posed by invasive species, and the need for greater protection of some of the world's last great remote areas.

Molecular Characterization and Expression Analyses of the Complement Component C8α, C8ß and C9 Genes in Yellow Catfish (Pelteobagrus fulvidraco) after the Aeromonas hydrophila Challenge.

The complement components C8α, C8ß and C9 have important roles in the innate immune system against invading microorganisms. Partial cDNA sequences of the Pf_C8α, Pf_C8ß and Pf_C9 genes (Pf: abbreviation of Pelteobagrus fulvidraco) were cloned from yellow catfish. The Pf_C8α, Pf_C8ß and Pf_C9 genes showed the greatest amino acid similarity to C8α (54%) and C8ß (62%) of zebrafish and to C9 (52%) of grass carp, respectively. Ontogenetic expression analyses using real-time quantitative PCR suggested that the three genes may play crucial roles during embryonic and early larval development. The mRNA expressions of the three genes were all at the highest levels in liver tissue, and at lower or much lower levels in 16 other tissues, demonstrating that the liver is the primary site for the protein synthesis of Pf_C8α, Pf_C8ß and Pf_C9. Injection of Aeromonas hydrophila led to up-regulation of the three genes in the spleen, head kidney, kidney, liver and blood tissues, indicating that the three genes may contribute to the host's defense against invading pathogenic microbes. An increased understanding of the functions of the Pf_C8α, Pf_C8ß and Pf_C9 genes in the innate immunity of yellow catfish will help enhance production of this valuable freshwater species.

Seafloor massive sulfide deposits support unique megafaunal assemblages: Implications for seabed mining and conservation.

Mining of seafloor massive sulfides (SMS) is imminent, but the ecology of assemblages at SMS deposits is poorly known. Proposed conservation strategies include protected areas to preserve biodiversity at risk from mining impacts. Determining site suitability requires biological characterisation of the mine site and protected area(s). Video survey of a proposed mine site and protected area off New Zealand revealed unique megafaunal assemblages at the mine site. Significant relationships were identified between assemblage structure and environmental conditions, including hydrothermal features. Unique assemblages occurred at both active and inactive chimneys and are particularly at risk from mining-related impacts. The occurrence of unique assemblages at the mine site suggests that the proposed protected area is insufficient alone and should instead form part of a network. These results provide support for including hydrothermally active and inactive features within networks of protected areas and emphasise the need for quantitative survey data of proposed sites.

WITHDRAWN: First record and distribution of the black pygmy mussel, Limnoperna securis (Lamarck, 1819) in the eastern Adriatic and Ionian seas.

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The complete mitochondrial genome of the deep-sea stony coral Solenosmilia variabilis (Scleractinia, Caryophylliidae) and its inter-individual variation.

Three individual-specific DNA libraries of the deep-sea scleractinian coral Solenosmilia variabilis (Duncan, 1873) were constructed to obtain complete mitochondrial genomes using the 454 Life Science pyrosequencing system. Two mitogenomes were successfully assembled: both were 15,968 bp in length, with base composition of A (24.2%), T (41.1%), C (13.7%) and G (21.0%). The genome contains 13 protein-coding genes, 2 ribosomal RNA genes, 2 transfer RNA genes and a D-loop region. The two mitogenomes were almost identical, with only 5 nucleotide differences (0.03%), including a synonymous substitution within the nad1, nad2 and nad4L genes, and two transversions in the D-loop region. This inter-individual variation indicates that these genes and/or region are potential candidates as molecular markers for population genetic research. The mitogenome of S. variabilis will be useful for future phylogenetic and phylogeographic studies of deep-sea corals.