Research Article |
Corresponding author: Chong Chen ( cchen@jamstec.go.jp ) Academic editor: Martin Haase
© 2022 Chong Chen, Hiromi Kayama Watanabe.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Chen C, Watanabe HK (2022) A new provannid snail (Gastropoda, Abyssochrysoidea) discovered from Northwest Eifuku Volcano, Mariana Arc. ZooKeys 1112: 123-137. https://doi.org/10.3897/zookeys.1112.85950
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Gastropods in the family Provannidae are characteristic members of deep-sea chemosynthesis-based communities. Recently, surveys of hydrothermal vents and hydrocarbon seeps in the western Pacific have revealed a high diversity of provannids, with new discoveries continuing to be made. Here, we report and describe a further new species, Provanna exquisita sp. nov., discovered from the Northwest Eifuku volcano on the Mariana Arc. This new species is distinguished from all other described Provanna species by its exaggerated sculpture characterised by two to three sharply raised, flange-like keels on the teleoconch whorls. The status of P. exquisita sp. nov. is also supported by a molecular phylogeny reconstruction using the mitochondrial cytochrome c oxidase subunit I (COI) gene, which suggested that it is most closely related to a clade of three species described from Okinawa Trough vents including P. clathrata, P. subglabra, and P. fenestrata. Despite being one of the better-explored regions of the world in terms of hydrothermal vent biodiversity, new discoveries like P. exquisita sp. nov. continue to remind us that we are nowhere near fully documenting the species diversity in these unique ecosystems—despite the species being threatened from imminent anthropogenic impacts such as deep-sea mining.
Deep sea, hydrothermal vent, Mollusca, new species, Provannidae, Western Pacific
Hydrothermal vent ecosystems in the deep sea host lush biological communities sustained by microbial chemosynthesis using hydrogen sulfide and other reducing substances dissolved in the vent fluid. First discovered in 1977 on the Galápagos Rift (
Gastropod molluscs are prevailing inhabitants of vent ecosystems (
Provanna is the most species-rich abyssochrysoid genus, with 27 described species inhabiting hot vents, cold seeps, and organic falls between 450–5687 m deep around the globe (
Provannid snails were collected from near the summit of NW Eifuku Volcano, Mariana Arc (Fig.
In situ habitat of Provanna exquisita sp. nov. on the summit of Northwest Eifuku Volcano. A overview of the habitat showing dominance by the deep-sea mussel Bathymodiolus septemdierum B close-up of the mixed provannid aggregation, arrowheads indicate examples of P. exquisita sp. nov. Photos taken by ROV ROPOS on dive #792 in Champagne vent, 21°29.25'N, 144°02.49'E, 1608 m deep.
Provannid snails were observed and dissected under an Olympus SZX7 dissecting microscope and photographs were taken using a digital single reflex camera (Olympus OM-D E-M5 Mark III) mounted on the trinocular. For specimen photos, several photos taken at different focus levels were stacked automatically using Adobe Photoshop 2022 software. Shell height (SH), shell width (SW), aperture height (AH), and aperture width (AW) were measured using digital Vernier callipers, with the values rounded up to the nearest 0.1 mm. In specimens with a damaged aperture, only SH and SW were taken.
The radula was dissected from the radula sac using fine tweezers and placed in 5% sodium hypochlorite solution to dissolve any remaining soft tissue, for about 5 min. The operculum was dissected and sulfide deposits on the surface were cleaned off using a soft brush. The radula and operculum were washed twice in Milli-Q water before mounting on aluminium stubs using carbon tape for scanning electron microscopy (SEM). A tabletop SEM (Hitachi TM3000) was used for observation and imaging of the radula and operculum.
Genomic DNA was extracted from a section of the provannid snail’s foot musculature using the QIAGEN DNeasy Blood and Tissue Kit (QIAGEN, Tokyo, Japan) following the manufacturer’s standard instructions and then purified using GeneReleaser (BioVentures Inc., Marfreesboro, USA) also following the manufacturer’s protocol. The quality of the extracted DNA was checked using a Thermo Scientific NanoDrop 2000 spectrophotometer. The Provanna-specific primer pair for the mitochondrial COI gene, Pg394L (5’-CTGATTTTTCGGACATCCTG-3’) and Pg1253R (5’-TGTTGAGGAAAGAAAGTAATATTAA-3’) were used for amplification via polymerase chain reaction (PCR) in a 20 μl reaction volume consisting of 1 μl template DNA, 1 μl of each primer, 10 μl of Premix ExTaq HS DNA polymerase (TaKaRa, Shiga, Japan) and 7 μl de-ionized sterilized water. A Veriti Thermal Cycler (Applied Biosystems) was used for PCR with the following protocol: 94 °C for 2 min followed by 30 cycles of (94 °C for 30 s, 45 °C for 30 s, 72 °C for 30 s), ending with 72 °C for 90 s. The successful PCR product was purified using ExoSAP-IT (Affymetrix) following standard protocols and submitted to FASMAC Corporation (Kanagawa, Japan) for Sanger sequencing. Sequencing was done using the universal primer HCO2198 (
Geneious Prime 2021.2.2 (https://www.geneious.com/) was used to align and manually correct the sequences obtained into a consensus sequence, deposited in GenBank under the accession number ON324570. This newly generated sequence of the NW Eifuku Provanna and a sequence of Cordesia atlantica Souza, Passos, Shimabukuro & Sumida, 2020 (
Phylogenetic reconstruction was conducted using Bayesian inference with MrBayes v. 3.2 (
Specimens examined in the present study were deposited in public museum collections, including Museum national d’Histoire naturelle (
Subclass Caenogastropoda Cox, 1960
Superfamily Abyssochrysoidea Tomlin, 1927
Provanna lomana (Dall, 1918).
Provanna aff. fenestrata
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Hydrothermal vent near the summit of Northwest Eifuku Volcano (
Holotype
(Fig.
Provanna exquisita sp. nov., type specimens A–D holotype (
A large Provanna reaching over 13 mm in shell height (exceeds 15 mm if spire intact), teleoconch whorls with two or three sharply raised, flange-like spiral keels crossing with weaker axial ribs to form a regularly latticed sculpture.
Shell (Fig.
Periostracum thick, golden brown.
Operculum (Fig.
Radula (Fig.
Gross external anatomy examined to limited extent with 2 brittle, ethanol-preserved specimens, revealing no notable deviations from published accounts for its genus (
So far, it is only known from a hydrothermal vent field on the summit of Northwest Eifuku Volcano, Mariana Arc. In addition to the Golden Lips site where specimens were collected, it has also been visually confirmed from the Champagne site 40 m away (Fig.
Exquisita (Latin, feminine adjective in the nominative singular), meaning “inquiring” or “exquisite”.
The striking shell sculpture of Provanna exquisita sp. nov., especially the prominent sharply raised spiral keels, is unique among described Provanna species. The species with the closest morphology is Provanna fenestrata Chen, Watanabe & Sasaki, 2019 described from Okinawa Trough vents and also recently reported from a methane seep in the South China Sea (
A number of other Provanna species also exhibit reticulate shell sculpture, including P. clathrata Sasaki, Ogura, Watanabe & Fujikura, 2016 from Okinawa Trough vents, Provanna pacifica (Dall, 1908) from seeps in Gulf of Panama and Oregon Margin, Provanna muricata Warén & Bouchet, 1986 from Galápagos Rift vents, P. admetoides Warén & Ponder, 1991 from Florida Escarpment seeps, P. segonzaci Warén & Ponder, 1991 from Lau Basin vents, Provanna buccinoides Warén & Bouchet, 1993 from Lau and North Fiji vents, and Provanna reticulata Warén & Bouchet, 2009 from seeps off West Africa. However, compared to P. exquisita sp. nov. all of these species exhibit much weaker spiral sculpture (
The phylogenetic tree of the superfamily Abyssochrysoidea reconstructed with Bayesian inference using the mitochondrial COI gene is shown in Fig.
The phylogenetic reconstruction herein recovered Provannidae as a paraphyletic clade, agreeing with previous studies (
Provanna exquisita sp. nov. is a large species for its genus. If the spires of specimens examined were intact it would be similar in size or even exceed that of the largest known Provanna species, P. cingulata Chen, Watanabe & Ohara, 2018 from a serpentinite-hosted system in Mariana Trench, which is known to reach 16.5 mm with a slightly corroded spire (
The discovery of Provanna exquisita sp. nov. from the Mariana Arc adds to the diversity of known abyssochrysoid from hydrothermal vents on the IBM Arc. In contrast, on the Izu-Ogasawara (Bonin) Arcs, only two provannid genera, Desbruyeresia and Alviniconcha, have been reported despite considerable sampling efforts (
We thank the captains and crew of R/V “Roger Revelle” and R/V “Thomas G. Thompson” for their excellent support of scientific activity during the SROF 2014 expedition (cruise RR1413) and SROF 2004 expedition (cruise TN167), respectively. We extend this thanks to the pilots and technical teams of ROVs JASON II and ROPOS, as well as all on-board scientists. The SROF 2014 expedition was funded by the United States National Oceanic and Atmospheric Administration (NOAA) Earth-Oceans Interaction Program and the SROF 2004 expedition was funded through the NOAA Ocean Exploration Program, the NOAA Vents Program. Verena Tunnicliffe (University of Victoria) is gratefully acknowledged for collecting the specimens examined and for providing them to us for study. We appreciated helpful comments from Winston Ponder (The Australian Museum) and Anders Warén (Swedish Museum of Natural History) which improved an earlier version of this paper. CC conceived and designed the study. CC conducted morphological examination and microscopy. HKW carried out DNA sequencing, the molecular data obtained was analysed by CC and HKW. CC interpreted the data and drafted the original manuscript, to which HKW contributed. Both authors approved the submission and agreed to its publication in the present form. Newly obtained COI sequence was deposited in GenBank (accession number ON324570). All specimens used in the present study were deposited in the Museum national d’Histoire naturelle (
KML file of the type locality of Provanna exquisita sp. nov.
Data type: Occurence
Explanation note: KML file of Golden Lip site, NW Eifuku Volcano, the type locality of Provanna exquisita sp. nov.