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Dr. Chong CHEN

Dr. Chong CHEN

Deep-sea biologist. Malacologist. Evolutionary biologist. "Mollusc collector", photographer.

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Gallery of Publications

A new co-authored paper in BMC Genomics led by Yi Lan uses transcriptomics to look at molecular adaptation in the deep-sea fish Aldrovandia affinis (Günther, 1877) (Actinopterygii: Halosauridae). Open Access: https://doi.org/10.1186/s12864-018-4720-z<br /> <br /> Abstract<br /> <br /> High hydrostatic pressure and low temperatures make the deep sea a harsh environment for life forms. Actin organization and microtubules assembly, which are essential for intracellular transport and cell motility, can be disrupted by high hydrostatic pressure. High hydrostatic pressure can also damage DNA. Nucleic acids exposed to low temperatures can form secondary structures that hinder genetic information processing. To study how deep-sea creatures adapt to such a hostile environment, one of the most straightforward ways is to sequence and compare their genes with those of their shallow-water relatives. We captured an individual of the fish species Aldrovandia affinis, which is a typical deep-sea inhabitant, from the Okinawa Trough at a depth of 1550 m using a remotely operated vehicle (ROV). We sequenced its transcriptome and analyzed its molecular adaptation. We obtained 27,633 protein coding sequences using an Illumina platform and compared them with those of several shallow-water fish species. Analysis of 4918 single-copy orthologs identified 138 positively selected genes in A. affinis, including genes involved in microtubule regulation. Particularly, functional domains related to cold shock as well as DNA repair are exposed to positive selection pressure in both deep-sea fish and hadal amphipod. Overall, we have identified a set of positively selected genes related to cytoskeleton structures, DNA repair and genetic information processing, which shed light on molecular adaptation to the deep sea. These results suggest that amino acid substitutions of these positively selected genes may contribute crucially to the adaptation of deep-sea animals. Additionally, we provide a high-quality transcriptome of a deep-sea fish for future deep-sea studies.
A new co-authored paper published in Royal Society Open Science led by Hiromi Watanabe-Kayama describes a new species of deep-sea stalked barnacle from Indian Ocean hydrothermal vents: Neolepas marisindica Watanabe, Chen & Chan in Watanabe et al., 2018. Furthermore, we also carried out phylogeographic investigation of deep-sea eolepadid stalked barnacles, leading to a better understanding of their evolution and biogeography. The paper is Open Access and available here: http://rsos.royalsocietypublishing.org/content/5/4/172408<br /> <br /> Abstract: <br /> Phylogeography of animals provides clues to processes governing their evolution and diversification. The Indian Ocean has been hypothesized as a ‘dispersal corridor’ connecting hydrothermal vent fauna of Atlantic and Pacific oceans. Stalked barnacles of the family Eolepadidae are common associates of deep-sea vents in Southern, Pacific and Indian oceans, and the family is an ideal group for testing this hypothesis. Here, we describe Neolepas marisindica sp. nov. from the Indian Ocean, distinguished from N. zevinae and N. rapanuii by having a tridentoid mandible in which the second tooth lacks small elongated teeth. Morphological variations suggest that environmental differences result in phenotypic plasticity in the capitulum and scales on the peduncle in eolepadids. We suggest that diagnostic characters in Eolepadidae should be based mainly on more reliable arthropodal characters and DNA barcoding, while the plate arrangement should be used carefully with their intraspecific variation in mind. We show morphologically that Neolepas specimens collected from the South West Indian Ridge, the South East Indian Ridge and the Central Indian Ridge belong to the new species. Molecular phylogeny and fossil evidence indicated that Neolepas migrated from the southern Pacific to the Indian Ocean through the Southern Ocean, providing key evidence against the ‘dispersal corridor’ hypothesis. Exploration of the South East Indian Ridge is urgently required to understand vent biogeography in the Indian Ocean.<br /> <br /> Watanabe HK*, Chen C, Marie DP, Takai K, Fujikura K, Chan BKK* (2018). Phylogeography of hydrothermal vent stalked barnacles: a new species fills a gap in the Indian Ocean ‘dispersal corridor’ hypothesis. Royal Society Open Science, 5: 172408. DOI: 10.1098/rsos.172408
A co-author paper of mine, led by Dr. Tomoyuki Komai from Chiba Natural History Museum and Institute, has been published in the journal Zootaxa. In this paper, we describe two new species of shrimps in genus Metacrangon (Caridea: Crangonidae) from hydrothermally influenced areas in Okinawa Trough, Japan. Please let me know if you would like to see the PDF. http://www.mapress.com/j/zt/article/view/zootaxa.4410.1.5 <br /> <br /> Abstract: <br /> Two new species of the crangonid shrimp genus Metacrangon Zarenkov, 1965, are described and illustrated on the basis of materials collected from the Okinawa Trough, Ryukyu Islands, southern Japan, during diving operations of remotely operated vehicles (ROVs): M. ryukyu n. sp. from off Iheya Island, at depth of 986 m; and Metacrangon kaiko n. sp. from NE of Yonaguni Island, at depth of 2205 m. The two new species resemble members of the M. munita (Dana, 1852) species group, but are both characteristic in having setose dactyli on pereopods 4 and 5. Some minor differences in morphology and genetic analysis using partial sequences of the barcoding mitochondrial COI gene support the recognition of the two new species. Holotypes of the two new species were collected from hydrothermally influenced areas, representing a previously unknown habitat for species of Metacrangon. <br /> <br /> Komai T*, Chen C, Watanabe HK (2018). Two new species of the crangonid genus Metacrangon Zarenkov, 1965 (Crustacea: Decapoda: Caridea) from the Okinawa Trough, Japan. Zootaxa, 4410(1): 97-112. DOI: 10.11646/zootaxa.4410.1.5
A paper I co-authored has been published in Molecular Phylogenetics and Evolution! In this work led by Yanjie Zhang, we sequenced mitochondrial genomes from deep-sea scale worms (Annelida: Aphroditiformia) to study their phylogeny and evolution. Here's a link that gives you free access to the full paper for the next 50 days: https://authors.elsevier.com/c/1Wt5g3m3nMqWNm<br /> <br /> Highlights<br /> <br /> - We recovered 15 mitochondrial genomes and 16 18S and 28S genes from 16 scale worms.<br /> - Eulepethidae and Aphroditidae are sister to the other families.<br /> - Branchinotogluminae and Macellicephalinae are paraphyletic.<br /> - Mitochondrial gene orders of deep-sea species have two novel arrangement patterns.<br /> - Mitochondrial genomes of deep-sea species show relaxed purifying selection. <br /> <br /> Zhang Y, Sun J, Rouse GW, Wiklund H, Pleijel F, Watanabe HK, Chen C, Qian P-Y, Qiu J-W* (2018). Phylogeny, evolution and mitochondrial gene order rearrangement in scale worms (Aphroditiformia, Annelida). Molecular Phylogenetics and Evolution, 125: 220-231. DOI: 10.1016/j.ympev.2018.04.002
Co-authored paper describing hydrothermal vent scale worms (Polychaeta: Polynoidae) has been just published in Frontiers in Marine Science (sorry its not molluscs this time)! It is Open Access and free for all to read here: https://www.frontiersin.org/articles/10.3389/fmars.2018.00112/<br /> <br /> In this paper, we described two new vent polynoides including Levensteiniella undomarginata Zhang, Chen & Qiu, 2018 and Branchinotogluma elytropapillata Zhang, Chen & Qiu, 2018; and also redescribed Lepidonotopodium okinawae Sui & Li, 2017 and Branchinotogluma japonicus Miura &Hashimoto, 1991 to include both sex forms. These scale worms are highly sexually dimorphic and in many cases the two sexes have been described as separate species or even genera, highlighting the importance of describing morphological characteristics of both sexes. <br /> <br /> Zhang Y, Chen C, Qiu J-W* (2018). Sexually dimorphic scale worms (Annelida: Polynoidae) from deep-sea hydrothermal vents in the Okinawa Trough: Two new species and two new sex morphs. Frontiers in Marine Science, 5: 112. DOI: 10.3389/fmars.2018.00112
Our short paper describing the strange behaviour of forming hanging 'stacks' exhibited by the vent snail genus Gigantopelta has been published in the journal Plankton and Benthos Research! This behaviour is probably related to reproduction. The paper is open access and available for view here: https://doi.org/10.3800/pbr.13.25<br /> <br /> “Mating stacks” have been widely documented in calyptraeid slipper limpets, which are protandric and exhibit sequential hermaphroditism. Gigantopelta is a genus of peltospirid snails endemic to deep-sea hydrothermal vents containing two species, one distributed on the East Scotia Ridge in the Southern Ocean and another on the Southwest Indian Ridge in the Indian Ocean. Here, we report the observation that both species form extensive (often >15 individuals) “snail chains”. These chains are potentially analogous to ‘mating stacks’ of calyptraeids, or alternatively, maybe a behaviour to facilitate spermatophore transfer. Both Gigantopelta species apparently have separate sexes and are sexually mature at a small size. However, it remains unclear whether they undergo sex change during their life. <br /> <br /> Chen C*, Marsh L, Copley JT (2018). Is it sex in chains? Potential mating stacks in deep-sea hydrothermal vent snails. Plankton and Benthos Research, 13(1): 25-27.
A co-authored paper with Muricidae experts Roland Houart and Chris Moe, describing three new muricid gastropods from the western Pacific, has been published in The Nautilus! This is my last paper for 2017 and the 13th this year! <br /> <br /> Of the three muricids described in this paper, one is a Chicomurex from the Philippines and Kwajalein Atoll – Chicomurex excelsus Houart, Moe & Chen, 2017. With live-taken specimens known from 150~200 m deep (dead shells have been found as shallow as 60 m), this species is characterised by a long siphonal canal which carries intricately webbed fronds but lacks in strong recurved spines. This unique siphonal canal sculpture, as well as a lower spire and a more angular final teleoconch whorl, separate it from C. gloriosus (Shikama, 1977), the closest congener which it co-occurs with. The other two species described are from Fiji and in the genus Chicoreus (Triplex) – Chicoreus kaitomoei Houart, Moe & Chen, 2017 and Chicoreus aquilus Houart, Moe & Chen, 2017, both being small-sized (<40 mm) for the genus. Although C. kaitomoei has been confused with C. aculeatus (Lamarck, 1822) and C. nobilis Shikama, 1977, these two species have multispiral protoconchs implying planktotrophic development unlike C. kaitomoei which has a pausispiral protoconch implying lecithotrophic development. The teleoconch of C. kaitomoei is by very short variceal spines (except those from P1-3) and a siphonal canal with three abapically bent spines concentrated on the anterior half. This species inhabit shallow waters around 9~30 m deep and is named after Kaito Moe, son of Chris Moe. Finally, C. aquilus which is only known from the holotype taken from 31~40 m deep in Fiji, is a highly distinctive species closest to C. rubescens (Broderip, 1833) and a few other species belonging to Chicoreus “group 2” (sensu Houart, 1992) but easily distinguished by differences in varice and aperture characteristics. <br /> <br /> Houart R*, Moe C, Chen C (2017). Description of three new muricids (Gastropoda: Muricidae: Muricinae) from the Philippines and Fiji. The Nautilus, 131(4): 207-216.
A new paper on the discovery of a new hydrothermal vent field has been published in the peer-reviewed Open Access journal Royal Society Open Science! I acted as the corresponding author. Read for free here: http://rsos.royalsocietypublishing.org/content/4/12/171570<br /> <br /> We report, in this paper, the discovery of the “Yokosuka” site – the deepest and hottest hydrothermal vent field in the Okinawa Trough, Japan. At 2190 m deep, this new vent field is highly active and exhibit vigorous focused venting from ‘black smoker’ chimneys, the highest temperature recorded being 364°C. We named the new vent site after R/V Yokosuka, the supporting vessel of DSV Shinkai6500 and AUV URASHIMA.<br /> <br /> Fauna and microbiota in the new site were generally similar to other Okinawa Trough vents, although with some different characteristics. For fauna, the dominance of the deep-sea mussel Bathymodiolus aduloides is surprising given other nearby vent sites are usually dominated by B. platifrons and/or B. japonicus, and a sponge field in the periphery dominated by Poecilosclerida is unusual for vents in this region. In terms of microbiota, the H2-rich vent fluids in one of the chimneys resulted in the dominance of hydrogenotrophic chemolithoautotrophs such as Thioreductor and Desulfobacterium. In terms of vent fluid, notable Cl depletion (130 mM) and high concentrations of both H2 and CH4 (~10 mM) probably result from subcritical phase separation and thermal decomposition of sedimentary organic matter. Our insights from the Yokosuka site implies that although the distribution of vent animal species may be linked to depth, the constraint is perhaps not water pressure and resulting chemical properties of the vent fluid but instead physical properties of the surrounding seawater. <br /> <br /> Miyazaki J, Kawagucci S, Makabe A, Takahashi A, Kitada K, Torimoto J, Matsui Y, Tasumi E, Shibuya T, Nakamura K, Horai S, Sato S, Ishibashi J, Kanzaki H, Nakagawa S, Hirai M, Takaki Y, Okino K, Watanabe HK, Kumagai H, Chen C* (2017). Deepest and hottest hydrothermal activity in the Okinawa Trough: Yokosuka site at Yaeyama knoll. Royal Society Open Science, 4: 171570. http://dx.doi.org/10.1098/rsos.171570
Lead-authored paper published in Zootaxa today! This paper describes Astyris thermophilus Chen, Watanabe, Araya, 2017, the first Columbellidae species discovered from deep-sea hydrothermal vent ecosystems. Its Japanese name literally means "columbellid from the underworld". It was found at the Natsu site, Iheya North hydrothermal field, Okinawa Trough, just shy of 1100m depth. http://www.mapress.com/j/zt/article/view/zootaxa.4363.4.13<br /> <br /> Please let me know if you would like to have a PDF copy. <br /> <br /> Chen C*, Watanabe HK, Araya JF (2017). First columbellid species (Gastropoda: Buccinoidea) from deep-sea hydrothermal vents discovered in Okinawa Trough, Japan. Zootaxa, 4363(4): 592-596. DOI: 10.11646/zootaxa.4363.4.13
New lead-authored paper, announcing the discovery of two new peltospirid vent snails, has been published in the peer-reviewed Open Access journal Frontiers in Marine Science! Read for free here: https://doi.org/10.3389/fmars.2017.00392<br /> <br /> This paper describes two new species of small gastropods, belonging to the hydrothermal vent endemic family Peltospiridae, from the Longqi hydrothermal vent field (~2785 m deep) on the Southwestern Indian Ridge, Indian Ocean; a new genus was erected to house one of them. The descriptions are based on shell (protoconch, teleoconch, periostracum, shell microstructure), radula, as well as anatomical characters. Lirapex politus Chen et al., 2017 (~4.5 mm shell height) is the first Indian Ocean representative of genus Lirapex which is also known from eastern Pacific and mid-Atalantic vents, and differs from the other known congeners by its lack of obvious axial sculpture (hence ‘politus’, smooth), as well as a narrower umbilicus and the final 0.5 whorl of the teleoconch being less detached. Dracogyra subfuscus Chen et al., 2017 (~7 mm shell diameter) is a depressed, globular, coiled peltospirid with a dark periostracum; the genus Dracogyra Chen et al., 2017 was established for this species. It is most similar to Depressigyra globulus Warén & Bouchet, 1989 known from the eastern Pacific, but easily separated from it by a lack of basal notch in the aperture and a more depressed shell with narrower umbilicus. Furthermore, the radula of D. subfuscus is highly characteristic with the central tooth being very wide and compressed. A Bayesian phylogeny using the mitochondrial COI barcoding gene confirmed the placement of the two new species in clade Neomphalina and family Peltospiridae. The two new species co-occur with two giant holobiont peltospirids including the scaly-foot Chrysomallon squamiferum Chen et al., 2015 and Gigantopelta aegis Chen et al., 2015, and are sometimes found on their body surface. The two new species do not host endosymbiotic bacteria and gut contents suggest that they probably feed on microbial film on chimney surfaces, as well as epibionts of the two larger peltospirids. <br /> <br /> Chen C*, Zhou Y, Wang C, Copley JT (2017). Two new hot-vent peltospirid snails (Gastropoda: Neomphalina) from Longqi hydrothermal field, Southwest Indian Ridge. Frontiers in Marine Science, 4: 392. DOI: 10.3389/fmars.2017.00392
Lead-authored paper reporting the unexpected discovery of two very rare snails in two new hydrothermal vent sites is now published in the peer-reviewed Open Access journal PeerJ! Read for free at: https://peerj.com/articles/4121/<br /> <br /> In this paper, we report the discovery of two very rare gastropods – the calliostomatid Otukaia ikukoae Sakurai, 1994 and the muricid Abyssotrophon soyoae (Okutani, 1959) in newly located hydrothermal vent sites in the Okinawa Trough, Japan. One of the two new sites is named the “Fukai” site after the poisonous forest of the same name in the Studio Ghibli film “Nausicaä of the Valley of the Wind” (1984)! The discovery of these snails represent the second record of Calliostomatidae and the third Muricidae from vents, and also represent range extensions of both species to the southwest, by about 700 km in the case of O. ikukoae. Based on radular characteristics, O. ikukoae is returned to genus Otukaia from Tristichotrochus. Although this is the first time either species are observed in their natural habitat, both are considered to be occasional invaders of vent ecosystems from surrounding regular sea bottom and not vent endemics given their other records from non-vent environment as well as the fact that they were found in weak diffuse flow venting areas and not focused venting areas. Nevertheless, it is clear that they are able to tolerate, to a certain extent, environmental stresses associated with vents (e.g., raised heavy metal and hydrogen sulfide concentrations). This enables them to access to rich food supplies supported by chemosynthesis primary production, and suggest that vent periphery likely play a key role in the evolution of biological adaptation to hydrothermal vent environment. <br /> <br /> Chen C*, Watanabe HK, Miyazaki J, Kawagucci S (2017). Unanticipated discovery of two rare gastropod molluscs from recently located hydrothermally influenced areas in the Okinawa Trough. PeerJ, 5: e4121. http://dx.doi.org/10.7717/peerj.4121/
Lead-authored paper on shallow water hydrothermal vent molluscs published in journal Marine Biodiversity! Read online for free: http://rdcu.be/wKVR<br /> <br /> This paper reports diversity of molluscs inhabiting shallow water (10-30m deep only!) hydrothermal vent ecosystem off Kueishan Island, Taiwan. Unlike deep-sea hydrothermal vents no endemic molluscs were found, and the species present were a subset of species present in surrounding areas that are apprently able to tolerate the 'extreme' environment. We report a total of 13 core species including 12 gastropods and one chiton, and discuss their ecology at the shallow vents. <br /> <br /> Please let me know if you would like to have a PDF copy. <br /> <br /> Chen C*, Chan T-Y, Chan BKK (2017). Molluscan diversity in shallow water hydrothermal vents off Kueishan Island, Taiwan. Marine Biodiversity. https://doi.org/10.1007/s12526-017-0804-2
A co-authored paper about the mechanism of symbiosis in a deep-sea vent crustacean is now published in the journal "Deep Sea Research Part I": https://authors.elsevier.com/c/1Vm3k3RueHIHRB . <br /> <br /> Shinkaia crosnieri Baba & Williams, 1998 is a vent-endemic squat lobster with dense setae / hair on its ventral surface. Much like its distant (convergently evolved) cousin, the "yeti-crab" Kiwa, these setae are full of epibiotic bacteria. Recently, S. crosnieri became the first vent animal where the nutritional reliance on epibiotic bacteria was experimentally demonstrated. In this study, we take a step further and show that S. crosnieri actively utilises and produces water current that significantly increases the productivity (chemosynthetic activity) of its epibionts. This means the squat lobster is actively cultivating / farming its own food -- the first example of such behavioural adaptation demonstrated among epibiont-hosting animals inhabiting chemosynthetic ecosystems.<br /> <br /> Through a series of experiments measuring the rate of chemosynthesis (sulfide consumption rate), it was revealed that the rate in epibionts significantly increased when water current was produced. Then, living S. crosnieri individuals were shown to produce an endogenous water flow to the ventral setae through elegant current visualisation using fluorescent particles. Finally, behavioral experiment indicated that S. crosnieri likely exhibit rheotaxis in its natural habitat, meaning it uses existing water current in addition to self-generated ones to increase the productivity of its epibionts = food.<br /> <br /> Watsuji T, Tsubaki R, Chen C, Nagai Y, Nakagawa S, Yamamoto M, Nishiura D, Toyofuku T, Takai K (2017). Cultivation mutualism between a deep-sea vent galatheid crab and chemosynthetic epibionts. Deep-Sea Research Part I: Oceanographic Research Papers, 127: 13-20. DOI: 10.1016/j.dsr.2017.04.012
New co-authored paper published in the journal "Polar Biology"! The article can be read for free via the following link: http://rdcu.be/tWBe . <br /> <br /> In this paper, we characterised microbes associated with the recently discovered Antarctic vent snail Gigantopelta chessoia Chen et al., 2015. It has been known that this snail hosts endosymbionts in an much enlarged oesophageal gland, but the details about the symbiont's phylogenetic position has not been published. We show that the endosymbiont is a Gammaproteobacteria related to sulfur-oxidising bacteria from cold seeps and other animals living in chemosynthetic ecosystems. Also revealed is a more diverse epibiont community on the gill surface, including members belonging to Gamma, Epsilon and Deltaproteobacteria. Interestingly, the endosymbiont Gammaproteobacteria strain was also found on the gill surface but not in the surrounding water column. Given that juveniles of this species is regularly recovered from within the adults' mantle cavity, this suggests they may acquire the symbionts directly from the gills of adult snails. <br /> <br /> Heywood JL, Chen C, Pearce DA, Linse K (2017). Bacterial communities associated with the Southern Ocean vent gastropod, Gigantopelta chessoia: indication of intergenerational, horizontal symbiont transfer. Polar Biology. https://link.springer.com/article/10.1007%2Fs00300-017-2148-6
New co-authored paper (with Shinsuke Kawagucci and other colleagues) is now officially published in the Open Access journal Frontiers in Earth Sciences! Available from: http://journal.frontiersin.org/article/10.3389/feart.2017.00045/full/<br /> <br /> Long story short, we developed a new water sampler for collecting hydrothermal fluid and other geofluids in the deep-sea. This new sampler, the "WHATS-III", is capable of pressure-tight, flow-through sampling of four independent geofluids per submersible dive. We also present real data collected during field tests carried out in hydrothermal vents of the Indian Ocean and Okinawa Trough. <br /> <br /> Miyazaki J, Makabe A, Matsui Y, Ebina N, Tsutsumi S, Ishibashi J, Chen C, Kaneko S, Takai K, Kawagucci S (2017). WHATS-3: An improved flow-through gas-tight fluid sampler for deep-sea geofluid research. Frontiers in Earth Science, 5: 45. https://doi.org/10.3389/feart.2017.00045
New co-authored paper (with Yanjie Zhang, Jin Sun, Hiromi Watanabe-Kayama and others) on the adaptation and evolution of deep-sea vent/seep scale worms (polynoid polychaetes) published in Scientific Reports! The article is open access and free to read here: http://www.nature.com/articles/srep46205<br /> <br /> Scale worms inhabit a great variety of environments ranging from very shallow water down to kilometres deep and are often an important member of chemosynthetic ecosystems such as vents, often living in close proximity to hot black smokers. In this study, we sequenced the transcriptomes of two deep-sea scale worms inhabiting hydrothermal vents and hydrocarbon seeps and one shallow water counterpart that was rather closely related. By comparing the three transcriptomes, we were able to elucidate selective amino acid usage, positively selected genes, highly expressed genes, and potentially duplicated genes, thereby shedding light on how the scale worms evolved to become successful members of deep-sea chemosynthetic communities. These are the first deep-sea scale worm transcriptomes ever reported. <br /> <br /> Most significant among our findings was the significance of genes related to haemoglobin. The two deep-sea polynoids chosen for this study, in the genera Branchipolynoe and Lepidonotopodium, are shown to have adopted different yet equally effective ways to cope with the oxygen-poor chemosynthetic ecosystems. Branchipolynoe rapidly evolved a novel tetra-domain haemoglobin which is highly effective in oxygen transport, whereas Lepidonotopodium increased the expression levels of standard single-domain haemoglobin to four times as high as Branchipolynoe. These results indicate that dealing with hypoxic environment is a key element in becoming successful in deep-sea vents and seeps. <br /> <br /> PS. I know this is not a mollusc paper, but I am interested in all cool animals especially when they have evolved key adaptations to live in weird environments! And the importance of haemoglobin is not limited to scale worms, but also applies to molluscs. <br /> <br /> Zhang Y [Yanjie], Sun J, Chen C, Watanabe HK, Feng D, Zhang Y [Yu], Chiu JMY, Qian P-Y, Qiu J-W (2017). Adaptation and evolution of polynoid scale-worms (Annelida: Polynoidae): insights from transcriptome comparison among two deep-sea and a shallow-water species. Scientific Reports, 7: 46205. http://doi.org/10.1038/srep46205
New paper dealing with a 'cryptic species complex' of chitons published in Marine Biodiversity! Open access, please read here: http://bit.ly/2okQQ56<br /> <br /> In this work, we present a case study of a total-evidence approach to resolving difficult and perplexing 'cryptic species complexes'. A Pacific shallow water polyplacophoran mollusc (chiton) Leptochiton rugatus (Carpenter in Pilsbry, 1892) is supposed to have a very wide range from Japan to Baja California, but has been previously suggested to comprise several cryptic species. Our genetic haplotype network using specimens across the range revealed four discrete clusters. Most strikingly, the haplotype of L. rugatus sensu stricto (California to Baja California) was very different in structure from that of the cluster ranging from the panhandle of Alaska to Oregon. The latter was found to have extremely high side fidelity and patchy distribution, and we present evidence that it is likely a brooder. The difference in life-history strategies between these two clusters account for the differences in their genetic structure. Although morphological differences were observed, these were minor and insufficient to guarantee each as species-level lineages alone. Only with the difference in life-history strategy could they be confidently recognised as separate species, the latter we described as L. cascadiensis sp. nov. after the Cascadia costal bioregion which it inhabits. <br /> <br /> Things without names are difficult to rationalise, and are difficult to conserve; assigning names to species is therefore critical to understanding and conserving biodiversity.This study shows that combining evidence from molecules, morphology, and importantly life-history, is key to untangling 'cryptic species complexes' which have become increasingly discovered in the recent years. The take-home message: if you want to solve cryptic species problems, don't forget to look at their way of life!<br /> <br /> This is my first time getting involved with describing a chiton, yay! Chitons are awesome. <br /> <br /> Sigwart JD, Chen C (2017). Brooding behaviour explains patchy distribution in a shallow-water invertebrate (Mollusca: Polyplacophora: Lepidopleurida). Marine Biodiversity, First Online, DOI: 10.1007/s12526-017-0688-1
New co-authored paper published today in The Nautilus! Read: http://bit.ly/2o07dEe <br /> <br /> We discuss the potential impacts of deep-sea mining to molluscan biodiversity, especially with regards to exploiting active hydrothermal sulfide deposits. Take the famous scaly-foot gastropod Chrysomallon squamiferum as an example – it is only known from three hydrothermal vents in the Indian Ocean, each around 0.003 sq km or half the size of a football field. Two of the three scaly-foot sites are already under active mining exploration licenses from the International Seabed Authority (ISA), to China (2011-2026) and Germany (2015-2030); the last one is in the Mauritius exclusive economic zone and therefore not under ISA jurisdiction. In fact, only 37 vent sites have been detected (4 actually visited) in the Indian Ocean (area approx.. 73,550,000 sq km) and their total area adds up to a mere 0.27 sq km (check out the infographics)! Many of these are also within the areas licenced for mining. These explorations are due to begin very soon and no conservation measures are in place or proposed, whereas many terrestrial mollusks such as the two-lipped door snail Alinda biplicata have extensive reserves dedicated to their conservation. Economic and political pressures to exploit deep-sea vents are advancing far quicker than our scientific understanding of these ecosystems that unique animals such as the scaly-foot call home, putting them at risk. Conservation measures for vent animals are urgently needed, and seem warranted given their tiny, disjunct areas of distribution. <br /> <br /> Please let me know if you would like a PDF copy, as usual. <br /> <br /> The original idea of this work was presented at the “Mollusks in Peril” 2016 Forum at the Bailey-Matthews National Shell Museum. <br /> <br /> Sigwart JS, Chen C, Marsh L (2017). Is mining the seabed bad for mollusks? The Nautilus 131(1): 43-50.
New first-authored paper published in BMC Evolutionary Biology ( http://bit.ly/3DGIGANTO ) reveals that two neomphaline hydrothermal vent gastropods, Gigantopelta and the 'scaly-foot' Chrysomallon, convergently evolved the peculiar adaptation of housing endosymbiotic bacteria in their much enlarged oesophageal gland. We first confirmed the existence of endosymbionts in Gigantopelta using Transmision Electron Microscopy (TEM), and then carried out serial sectioning and 3D reconstruction for a juvenile specimen of Gigantopelta chessoia along with dissections of the adult. These revealed many key anatomical differences with the 'scaly-foot gastropod' pointing towards two independent origins of a similar way of life, confirmed by a 5-gene phylogenetic reconstruction clearly showing that the two are not sister within the known members of Peltospiridae. By comparing Gigantopelta and Chrysomallon, we show that metazoans are capable of rapidly and repeatedly evolving equivalent anatomical adaptations and close-knit relationships with chemoautotrophic bacteria, achieving the same end-product through parallel evolutionary trajectories.<br /> <br /> The paper is open access and available freely: http://bmcevolbiol.biomedcentral.com/articles/10.1186/s12862-017-0917-z<br /> <br /> We also included an interactive 3D anatomical model of Gigantopelta, you only need a PDF reader to play around with it! Have fun! It is available here: https://static-content.springer.com/esm/art%3A10.1186%2Fs12862-017-0917-z/MediaObjects/12862_2017_917_MOESM1_ESM.pdf
A new first-authored paper (http://bit.ly/2g4qYmQ) has been published in Journal of the Marine Biological Association of the United Kingdom! This paper describes Provanna cingulata n. sp., from Shinkai Seep Field, a serpentinisation-hosted ecosystem 5700 m deep in the Mariana Trench. It is the deepest and largest member of genus Provanna, which is endemic to chemosynthetic ecosystems. Unlike most Provanna species which either have prominent lattice sculpture or completely smooth, this species is characterised by prominent spiral sculpture but lacking in axial sculpture. Please let me know if you would like to have a PDF copy :)
New co-authored paper published in the journal Geochemistry, Geophysics, Geosystems! Link: http://bit.ly/2dhKMSF <br /> <br /> This study reports three types of brucite-carbonate chimneys from the deepest known serpentinite-hosted vent in the world, the 5700 m deep Shinkai Seep Field in Mariana forearc. Although mainly a geochemistry/geology paper, the chimneys are inhabited by some megafaunal animals and brief descriptions of the colonies are included. Molluscs are also present, such as Provanna snails. The paper is open-access so anyone can read it for free! 🙂<br /> <br /> Okumura T, Ohara Y, Stern RJ, Yamanaka T, Onishi Y, Watanabe H, Chen C, Bloomer SH, Pujana I, Sakai S, Ishii T, Takai K (2016). Brucite chimney formation and carbonate alteration at the Shinkai 1 Seep Field, a serpentinite-hosted vent system in the Southern Mariana Forearc. Geochemistry, Geophysics, Geosystems, 75. DOI: 10.1002/2016GC006449
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