Placiphorella methanophila Vončina, 2024

(SOSA), Senckenberg Ocean Species Alliance, Brandt, Angelika, Chen, Chong, Engel, Laura, Esquete, Patricia, Horton, Tammy, Jażdżewska, Anna M., Johannsen, Nele, Kaiser, Stefanie, Kihara, Terue C., Knauber, Henry, Kniesz, Katharina, Landschoff, Jannes, Lörz, Anne-Nina, Machado, Fabrizio M., Martínez-Muñoz, Carlos A., Riehl, Torben, Serpell-Stevens, Amanda, Sigwart, Julia D., Tandberg, Anne Helene S., Tato, Ramiro, Tsuda, Miwako, Vončina, Katarzyna, Watanabe, Hiromi K., Wenz, Christian & Williams, Jason D., 2024, Ocean Species Discoveries 1 – 12 — A primer for accelerating marine invertebrate taxonomy, Biodiversity Data Journal 12, pp. e 128431-e 128431 : e128431-

Placiphorella methanophila Vončina sp. nov.

Placiphorella sp. nov.: Sellanes et al. 2004: 1066.

Placiphorella atlantica : Sellanes et al. 2008: 1105, non Placiphorella atlantica (A. E. Verrill & S. I. Smith in Verrill, 1882).

Placiphorella sp. : Schwabe and Sellanes 2010: 47, Figs. 14 I – J, 15.

Placiphorella sp. : Schwabe 2010: 172, Fig. 1 B, 174: Fig. 3 B, 188: Fig. 18 A.

Materials

Type status: Holotype. Occurrence: catalogNumber: ZSM Mol 20041044 ; recordedBy: Vessel R / V Kay Kay, leg. Javier Sellanes Lopez; individualCount: 1; lifeStage: adult; preparations: EtOH 75 %, partly disarticulated (ZSM Mol 20041044) | SEM stubs with parts of girdle, precephalic lappet and radula (ZSM Mol 20220314); otherCatalogNumbers: ZSM Mol 20220314; occurrenceID: 9A562FEA-D154-5A2D-9909-D3C42E9E754A; Taxon: scientificName: Placiphorella methanophila Vončina ; kingdom: Animalia; phylum: Mollusca; class: Polyplacophora; order: Chitonida ; family: Mopaliidae ; genus: Placiphorella ; specificEpithet: methanophila ; scientificNameAuthorship: Vončina; nomenclaturalCode: ICZN; Location: higherGeography: Pacific Ocean; continent: South America; country: Chile; stateProvince: Biobío Region, Concepción Province; locality: off Concepción ; minimumDepthInMeters: 870; maximumDepthInMeters: 930; verbatimLatitude: 36 ° 20 ' 60 '' S; verbatimLongitude: 73 ° 43 ' 60 '' W; Identification: identifiedBy: Enrico Schwabe; dateIdentified: 04 / 08 / 2008; Event: samplingProtocol: Agassiz trawl (AGT), 1.5 m wide, operated in 20 min. hauls; eventDate: 2003; habitat: shelf margin, on pieces of carbonate crusts; Record Level: institutionCode: SNSB-ZSM; collectionCode: Mol; basisOfRecord: PreservedSpecimen

Type status: Paratype. Occurrence: catalogNumber: SMF 376539 ; recordedBy: Vessel R / V Vidal Gormáz, leg. Javier Sellanes Lopez; individualCount: 1; lifeStage: adult; preparations: EtOH 75 %, partly disarticulated; otherCatalogNumbers: SMF 376539; occurrenceID: CC1E4F2E-B73F-5B2C-81F1-85EB904472DA; Taxon: scientificName: Placiphorella methanophila Vončina ; kingdom: Animalia; phylum: Mollusca; class: Polyplacophora; order: Chitonida ; family: Mopaliidae ; genus: Placiphorella ; specificEpithet: methanophila ; scientificNameAuthorship: Vončina; nomenclaturalCode: ICZN; Location: higherGeography: Pacific Ocean; continent: South America; country: Chile; stateProvince: Biobío Region, Concepción Province; locality: off Concepción ; maximumDepthInMeters: 922; verbatimLatitude: 36 ° 00.23 ’ S; verbatimLongitude: 73 ° 38.41 ’ W; Identification: identifiedBy: Enrico Schwabe; dateIdentified: 04 / 08 / 2008; Event: samplingProtocol: Agassiz trawl (AGT), 1.5 m wide, operated in 20 min. hauls; eventDate: 04 / 2007; Record Level: institutionCode: SMF; basisOfRecord: PreservedSpecimen

Type status: Paratype. Occurrence: catalogNumber: ZSM Mol 20080824 ; recordedBy: Vessel R / V Vidal Gormáz, leg. Javier Sellanes Lopez; individualCount: 2; lifeStage: adult; preparations: EtOH 95 %, a fragment of foot sampled for DNA barcoding; associatedSequences: https://www.ncbi.nlm.nih.gov/nuccore/PP133101; occurrenceID: CA9298E4-5204-5350-ACF9-4CC6547B5887; Taxon: scientificName: Placiphorella methanophila Vončina ; kingdom: Animalia; phylum: Mollusca; class: Polyplacophora; order: Chitonida ; family: Mopaliidae ; genus: Placiphorella ; specificEpithet: methanophila ; scientificNameAuthorship: Vončina; nomenclaturalCode: ICZN; Location: higherGeography: Pacific Ocean; continent: South America; country: Chile; stateProvince: Biobío Region, Concepción Province; locality: off Concepción ; maximumDepthInMeters: 922; verbatimLatitude: 36 ° 00.23 ’ S; verbatimLongitude: 73 ° 38.41 ’ W; Identification: identifiedBy: Enrico Schwabe; dateIdentified: 04 / 08 / 2008; Event: samplingProtocol: Agassiz trawl (AGT), 1.5 m wide, operated in 20 min. hauls; eventDate: 04 / 2007; Record Level: institutionCode: SNSB-ZSM; collectionCode: Mol; basisOfRecord: PreservedSpecimen

Description

Body of medium size (18–30 mm x 12–23 mm, holotype 30 mm x 23 mm), broadly oval, low-elevated, subcarinated, side slopes straight to slightly convex; valves not beaked or with small, not pronounced apex (Fig. 1 ). Tegmentum minutely and irregularly granulated, white or yellowish, usually mottled with brown along the posterior valve margins; girdle broadly expanded anteriorly, usually white mottled with light-brown and brown (Figs 1 , 2 ). See Schwabe and Sellanes (2010), Figs. 14 I – J and 15, for additional holotype photograph and detailed SEM photos of the girdle spicules and radula.

Head valve crescent-shaped, front slope straight, posterior margin very widely V-shaped, with a small median notch and little raised apex, tegmentum minutely and irregularly granulated, with some inconspicuous, irregular radial ridges and concentric growth lines (Figs 1 , 2 A and D). Intermediate valves broadly rectangular, very wide, with valve III being the widest, short, front margin widely angular, weakly projected forward at jugal part; side margins rounded, hind margin concave, apex weakly or not indicated, lateral areas raised, bordered by raised diagonal ribs, interspace shallowly excavated, crossed by conspicuous concentric growth lines (Figs 1 , 2 B and E). Tail valve small, roughly triangular in outline, about half as wide as widest intermediate valve, front margin straight to slightly convex, hind margin with a shallow or obsolete caudal sinus, mucro distinct, raised, terminal, overhanging, antemucronal area almost straight, postmucronal area slightly convex, tegmentum with two ribs separating the ante- and postmucronal areas (Fig. 2 C and F – G).

Articulamentum strongly developed, white, valves calloused, apophyses very wide, short, slightly rounded to subtrapezoidal, trapezoid in the tail valve, separated by a narrow jugal sinus, insertion plates short, slit formula 15–16 / 1 / sinus, slits shallow, no slit rays, teeth thick, bilobed and crenulated (Fig. 2 ).

Girdle broadly expanded anteriorly, uniformly brown or yellowish, dorsally covered with two kinds of spicules: single, smooth, and sharply pointed spicules, L: 75–100 μm (mean = 85 μm, n = 5), W: 15–25 μm (mean = 21, n = 5) and similar, but longer spicules gathered in groups of a few, L: 107–250 μm (mean = 120 μm, n = 12), W: 12–17 μm (mean = 15 μm, n = 5) (Fig. 3 A – C). Sparsely scattered (more numerous near the front) large bristles, beset with slender, smooth and sharply-pointed spicules, L: 268 μm (n = 1), W: 29–36 μm (mean = 32 μm, n = 4), arranged in oblique series along axis (Fig. 3 D). Marginal fringe composed of straight, smooth, sharp-topped spicules, L: 120–135 μm (mean = 125 μm, n = 3), W: 15–20 μm (mean = 17 μm, n = 5) (Fig. 3 D). Ventral girdle spicules smooth, flattened, L: 80 μm (n = 1), W: 18–20 μm (mean = 19 μm, n = 2). Pallial fold with 6–14 tentacles, up to 2 mm in length with the middle ones the longest, spicules of the precephalic tentacles smooth, sharply-pointed L: 120–150 μm (mean = 130 μm, n = 5), W: 15–20 μm (mean = 17 μm, n = 5) (Fig. 3 E).

Radula of holotype small, 5.8 mm in length, with 52 rows of teeth, of which 42 are of mature. Central tooth subrectangular, with wide base and curved blade, first lateral tooth elongate, wing-shaped with a narrow blade, major lateral tooth with tricuspid head, denticles pointed, central denticle somewhat longer than others, outer denticle widest and shallowest notched, first uncinal very prominent with high elevated lamellae, major uncinal elevated, slender with only slightly increased tip (Fig. 3 F).

Gills merobranchial, 13–18 ctenidia per side (15 and 18 on the left and right side, respectively, in the holotype) in specimens 18–30 mm long.

Diagnosis

Chitons of medium size, up to 30 mm, body broadly oval, girdle expanded anteriorly; colour of the tegmentum white or yellow, mottled with brown; girdle white with light-brown and brown maculation. Valves depressed, subcarinated, minutely and irregularly granulated. Tail valve roughly triangular in shape, mucro terminal, overhanging. Girdle covered with two kinds of spicules: single, smooth and sharply pointed spicules and similar, but longer spicules gathered in groups of a few; sparsely scattered large bristles beset with elongated slender spicules.

Molecular diagnosis: COI: 132 – C, 168 – G, 258 – A, 267 – C, 300 – T, 348 – C, 411 – A, 420 – A, 438 – G.

Etymology

The specific epithet methanophila is a feminine adjective formed from the Latin noun methanum = methane, and the suffix - phila = “ loving ”, “ friendly ” or “ friend ”, underlining the close association of the new species with methane seeps.

Distribution

At present, only known from off Concepción, Chile; all specimens found in close relationship to the methane seeps (see discussion of Chilean records of P. pacifica in Schwabe and Sellanes (2010): 48).

Taxon discussion

Phenotypic characters discussion:

There are five species that share a head valve incision number> 10 with Placiphorella methanophila sp. nov., namely Placiphorella atlantica (Verrill & S. I. Smith, 1882) , P. laurae Clark, 2019 , P. isaotakii Saito, Fujikura & Tsuchida, 2008 , P. okutanii Saito, Fujikura & Tsuchida, 2008 and P. pacifica S. S. Berry, 1919 . However, they differ from the new species by several characters, named below:

Placiphorella methanophila sp. nov. differs from P. atlantica (source: Kaas and Van Belle (1994); Clark (1994)) by the shape of the tail valve (see also Schwabe and Sellanes (2010), Figs. 14 J – L for comparison; triangular with the straight antemucronal area in P. methanophila sp. nov. vs. trapezoidal with the concave antemucronal area in P. atlantica ); sculpture of dorsal spicules (smooth, single and sharply pointed in P. methanophila sp. nov. vs. longitudinally striated and mamillated in P. atlantica ); by the sculpture and size of marginal spicules (smooth and 120–135 μm long in P. methanophila sp. nov. vs. striated and 80 μm long in P. atlantica );

Placiphorella methanophila sp. nov. differs from P. isaotakii (source: Saito et al. (2008)) by the sculpture of the tegmentum (minutely and irregularly granulated in P. methanophila sp. nov. vs. densely packed, elongate granules, occasionally merging into longitudinal threads in P. isaotakii ); by the girdle ornamentation (smooth, single and sharply pointed, 75–100 μm long and similar, but gathered in groups and longer, 107–250 μm in P. methanophila sp. nov. vs. spicules mamillated at tip 50 μm × 40 µm long and longer, grouped spicules, 440 µm long in P. isaotakii ); number of gills (13–18 gills in P. methanophila sp. nov. vs. 20–21 gills in P. isaotakii );

Placiphorella methanophila sp. nov. differs from P. laurae (source: Clark (2019)) by the shape of the tail valve (straight antemucronal area, obtuse triangle-shaped in P. methanophila sp. nov. vs. concave antemucronal area, acute-angle triangle in P. laurae ); length of dorsal spicules (107–250 μm long in P. methanophila sp. nov. vs. 400 μm long in P. laurae ); size of spicules of bristles: 268 x 29–36 μm in P. methanophila sp. nov. vs. 350 x 40 μm in P. laurae ;

Placiphorella methanophila sp. nov. differs from P. okutanii (source: Saito et al. (2008)) by the shape of the tail valve (widely triangular in outline in P. methanophila sp. nov. vs. inversed trapezoidal, less wide in P. okutanii ); by the dorsal girdle ornamentation (single sharply pointed spicules, 80–100 x 24–25 μm and similar, but clustered together spicules 107–250 μm x 12–17 μm in P. methanophila sp. nov. vs. spicules mamillated at tip 150 μm × 30 µm and longer, grouped spicules, 400 x 50 µm in P. okutanii );

Placiphorella methanophila sp. nov. differs from P. pacifica (source: Berry (1919)) by the sculpture of the tegmentum (minutely and irregularly granulated in P. methanophila sp. nov. vs. smooth in P. pacifica ); by the sculpture of the head valve (inconspicuous, irregular radial ridges in P. methanophila sp. nov. vs. 12-14 low, radiating ribs in P. pacifica ); position of the mucro (terminal in P. methanophila sp. nov. vs. subterminal in P. pacifica ).

Genetic discussion:

The ranges of uncorrected genetic p-distances between Placiphorella methanophila sp. nov. and all Placiphorella available from GenBank in mitochondrial cytochrome oxidase subunit 1 ( COI) gene sequences ranged from 4.1 % to 14.6 % (Table 1 ). The closest COI sequences are: KJ 574090 (4.1 % distance), representing Placiphorella sp. A from Irisarri et al. (2014), which was mentioned by authors as a potentially new species, but the description has never been published; and GU 806074 , GU 806077 -8, GU 806080 , GU 806115 and GU 806118 (4.6–5.0 % distance) representing P. atlantica , from which P. methanophila sp. nov. can be also differentiated morphologically.

Notes

Methods

Live animals were collected at depths of 870 – 930 m during two cruises along the Chilean coast. Collecting was done using a 1.5 m wide Agassiz trawl ( AGT), during hauls of 20 minutes. Specimens were fixed in 4 % buffered formalin and preserved in 75 % ethanol ( ZSM Mol 20041044 and SMF 376539) or directly preserved in 95 % ethanol ( ZSM Mol 20080824). The systematic classification follows Sirenko (2006) with slight modifications. The morphological terminology follows Schwabe (2010).

For scanning electron microscopy ( SEM), the valves and radula were removed, cleaned with a 5 % sodium hydroxide (NaOH) solution and rinsed in distilled water. The pieces of the perinotum were only air-dried. Objects were placed on SEM stubs using double-sided adhesive tabs. After coating with gold for 135 seconds in a Polaron sputter coater, they were examined with a LEO 1430 VP SEM. All figures were assembled in Adobe Photoshop CS 6.

For DNA barcoding, a small fragment of tissue from two chitons ZSM Mol 20080824 was sampled. DNA was extracted using QIAamp DNA Micro Kit ( QIAGEN), following the manufacturer’s protocol. The cytochrome oxidase subunit I ( COI primers LCO 1490 and HCO 2198; Folmer et al. (1994)) was amplified using repliQa HiFi ToughMix from ThermoFisher, following the PCR programme for COI in Bonfitto et al. (2011). Out of two samples, only one was amplified and sent for sequencing. The obtained sequence was manually inspected in Geneious Prime v. 2023.1 and was made publicly available on GenBank under the accession number PP 133101. Additionally, fourteen COI sequences of Placiphorella were downloaded from GenBank and aligned with the new sequence from this study, using default settings of MAFFT 7 ( Katoh et al. 2002, Katoh and Toh 2008) under the Q-INS-I strategy. Uncorrected pairwise distances were calculated using MEGA 11 ( Tamura et al. 2021). There was a total of 460 positions in the final dataset. The number of base differences per site from between sequences are shown in Table 1 . The molecular diagnosis of P. methanophila sp. nov. was composed in comparison with genetically closest Placiphorella (4.1–5.0 % in uncorrected genetic p-distances in COI) with DeSignate web application ( Hütter et al. 2020). The diagnostic molecular character (signature characters) for P. methanophila sp. nov. was defined as the position of a nucleotide in an alignment, which is monomorphic within each species and differs between species. Only binary positions, k-window = 1 and no deletions were used ( Hütter et al. 2020).

Abbreviations used in the text are as follows: BL – body length; L – length; W – width; ZSM Mol – Bavarian State Collection of Zoology; SMF – Senckenberg Research Institute and Natural History Museum Frankfurt, Frankfurt, Germany, ZIN – Zoological Institute of Russian Academy of Sciences, St. Petersburg, Russia.

Holotype ( ZSM Mol 20041044), now disarticulated: parts of girdle, precephalic lappet, radula, on three SEM stubs ZSM Mol 20220314 and two paratypes ZSM Mol 20080824 are deposited in the collection of Zoologische Staatssammlung München, Munich, Germany; a paratype SMF 376539 is deposited in the malacological collection of Senckenberg Research Institute and Natural History Museum Frankfurt, Frankfurt, Germany.

Figures

Figure 1. Placiphorella methanophila Vončina, sp. nov., dorsal view. A Holotype, ZSM Mol 20041044, body length: 29 mm; B Paratype, SMF 376539, body length: 26 mm. Scale bar: 5 mm.

Figure 2. Placiphorella methanophila Vončina, sp. nov. A, D Paratype. ZSM Mol 20080824; B, C, E – G Holotype, ZSM Mol 20041044. A – C. Valves I, VII, VIII, respectively, dorsal view; D – F Valves I, VII, VIII, respectively, ventral view; G Valve VIII, lateral view. Scale bar: 2 mm.

Figure 3. Placiphorella methanophila Vončina, sp. nov. A – B. Specimen from ZIN collection (ZIN 2587), photos by courtesy of Boris Sirenko. C – F. Holotype, ZSM Mol 20041044. A – B. Dorsal spicules of perinotum; C. Longer dorsal spicules of perinotum clustered in groups; D. Bristle with spicules and marginal spicules; E. Spicules of precephalic tentacles; F. Central portion of radula. Scale bars: 200 µm (A – D), 50 µm (E), 20 µm (F).