Category: Deep-sea

First Columbellidae snail from deep-sea vent

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

Astyris thermophilus. A–D. Holotype (UMUT RM32644). E. Paratype #1 (NSMT Mo 78990). F. Paratype #2(UMUT RM32645), periostracum removed to show spiral striae. G. Protoconch of paratype #6, a juvenile specimen (UMUT RM32646). H. Operculum of paratype #2 (UMUT RM32645). I. Radula of paratype #2, UMUT RM32645). Scale bars = 2 mm (A–F),500 μm (G, H), 20 μm (I).

  • 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

Two new vent snails from 2.8km deep in the Indian Ocean!

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

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.

Lirapex politus n. sp., scale bars = 1 mm.

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.

Dracogyra subfuscus n. gen., n. sp., scale bars = 1 mm.

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.

  • 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

Two rare gastropods from two new vents!

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/

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.

Specimens of the two gastropods collected from hydrothermally influenced areas.(A–D) Tristichotrochus ikukoae from Fukai site, Higashi-Ensei. (E–J) Abyssotrophon soyoae from Crane site, Tarama Hill; (E–H) Specimen #1, (I, J) Specimen #2. Scale bars: (A–D) 1 cm, (E–J) 0.5 cm.

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.

The Fukai site (above) and the Crane site (below).

  • 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/

New paper characterises microbes associated with Antarctic vent snail

New co-authored paper published in the peer-reviewed journal “Polar Biology“! The article can be read for free via the following link: http://rdcu.be/tWBe .

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.

Gigantopelta chessoia and its associated microbial community

New paper presents a new deep-sea fluid sampler

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/

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.

Overview of the WHATS-3 Sampler

  • 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 paper shows a vent squat lobster actively cultivates its epibionts!

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 . 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.

Dense ventral setae of S. crosnieri (left) and epibionts on the setae (right)

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.

Endogenous water flow generated by S. crosnieri, left: artist’s impression (by Emi Hada) and right: visualisation of the actual current speed generated

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 paper on adaptation of vent/seep scale worms published!

New co-authored paper on the adaptation and evolution of vent scale worms (polynoid polychaetes) published in Scientific Reports! The article is open access and free to read here: http://www.nature.com/articles/srep46205

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.

Highly expressed genes in B. pettiboneae (vent/seep), Lepidonotopodium sp. (vent) and H. imbricata (shallow water relative).(a) Percentage of genes participated in different cellular processes. (b) Expression level for gene groups participated in different cellular processes.

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.

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 on potential impacts of deep-sea mining published!

New co-authored paper published today in The Nautilus! [Link] The Nautilus is a peer-reviewed journal publishing articles on diverse aspects of the biology, ecology, and systematics of mollusks established in 1886.

In this new paper, 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.

Infographics giving an idea of the total area of detected hydrothermal vents in the Indian Ocean.


The original idea of this work was presented at the “Mollusks in Peril” 2016 Forum at the Bailey-Matthews National Shell Museum.

Sigwart JS, Chen C, Marsh L (2017). Is mining the seabed bad for mollusks? The Nautilus 131(1): 43-50.

New paper demonstrates convergent adaptation in vent snails!

New first-authored paper published in BMC Evolutionary Biology! [Link]

In the new paper, we reveal 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.


The paper is open access and available freely: http://bmcevolbiol.biomedcentral.com/articles/10.1186/s12862-017-0917-z

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

 

Chen C*, Uematsu K, Linse K, Sigwart JS (2017). By more ways than one: Rapid convergence in adaptations to hydrothermal vents shown by 3D anatomical reconstruction of Gigantopelta (Mollusca: Neomphalina). BMC Evolutionary Biology, 17:62. DOI: 10.1186/s12862-017-0917-z

 

New paper reports chimneys from 5700m deep in Mariana forearc

New co-authored, open-access paper published in the journal Geochemistry, Geophysics, Geosystems! [Link]

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!

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 Seep Field, a serpentinite-hosted vent system in the Southern Mariana Forearc. Geochemistry, Geophysics, Geosystems, 75. DOI: 10.1002/2016GC006449