Craspedochiton zefranki Vončina, 2025

(SOSA), Senckenberg Ocean Species Alliance, Andrade, Luiz F., Boyko, Christopher B., Brandt, Angelika, Buge, Barbara, Dávila Jiménez, Yasmín, Henseler, Mats, Hernández Alcántara, Pablo, Jóźwiak, Piotr, Knauber, Henry, Marcondes Machado, Fabrizio, Martínez-Muñoz, Carlos A., Momtazi, Farzaneh, Nakadera, Yumi, Qiu, Jian-Wen, Riehl, Torben, Rouse, Greg W., Sigwart, Julia D., Sirenko, Boris, Souza-Filho, Jesser F., Steger, Jan, Stępień, Anna, Tilic, Ekin, Trautwein, Bianca, Vončina, Katarzyna, Williams, Jason D. & Zhang, Junlong, 2025, Ocean Species Discoveries 13 – 27 — Taxonomic contributions to the diversity of Polychaeta, Mollusca and Crustacea, Biodiversity Data Journal 13, pp. e 160349-e 160349 : e160349-

Craspedochiton zefranki Vončina sp. nov.

Materials

Type status: Holotype. Occurrence: catalogNumber: MNHN-IM- 2019-34865 ; recordedBy: leg. Bouchet, Dayrat, Warén & Richer de Forges-IRD; individualCount: 1; lifeStage: adult; preparations: EtOH 100 %, partly disarticulated + SEM stubs with parts of girdle and radula; associatedSequences: GenBank nr PV 664593; occurrenceID: B359911D-085D-512F-8E8E-407151DD3145; Taxon: scientificName: Craspedochiton zefranki Vončina ; kingdom: Animalia; phylum: Mollusca; class: Polyplacophora; order: Chitonida ; family: Acanthochitonidae ; genus: Craspedochiton ; specificEpithet: zefranki ; scientificNameAuthorship: Vončina; nomenclaturalCode: ICZN; Location: higherGeography: Pacific Ocean; continent: Oceania; country: Solomon Islands; locality: NW San Cristobal ; minimumDepthInMeters: 97; maximumDepthInMeters: 223; verbatimLatitude: 10°17'S; verbatimLongitude: 161°43'E; Identification: identifiedBy: Katarzyna Vončina; dateIdentified: 21-04 - 2024; Event: eventDate: 06-10 - 2001; eventRemarks: Expedition: Solomon 1, Station: DW 1840, Ship: Alis; Record Level: institutionCode: MNHN; collectionCode: IM; basisOfRecord: PreservedSpecimen

Type status: Paratype. Occurrence: catalogNumber: SMF 380885 ; recordedBy: leg. Bouchet, Dayrat, Warén & Richer de Forges-IRD; individualCount: 1; lifeStage: adult; preparations: EtOH 100 %; otherCatalogNumbers: MNHN-IM- 2019-35217; occurrenceID: B12459B8-0BC6-59F6-805F-02F09F435567; Taxon: scientificName: Craspedochiton zefranki Vončina ; kingdom: Animalia; phylum: Mollusca; class: Polyplacophora; order: Chitonida ; family: Acanthochitonidae ; genus: Craspedochiton ; specificEpithet: zefranki ; scientificNameAuthorship: Vončina; nomenclaturalCode: ICZN; Location: higherGeography: Pacific Ocean; continent: Oceania; country: Solomon Islands; locality: NW San Cristobal ; verbatimLatitude: 10°17'S; verbatimLongitude: 161°43'E; Identification: identifiedBy: Katarzyna Vončina; dateIdentified: 2024-21 - 04; Event: eventDate: 06-10 - 2001; Record Level: institutionCode: SMF; basisOfRecord: PreservedSpecimen

Description

Body of small size ( holotype: 16 x 10 mm, paratype: 13 x 8 mm), oval, carinated, moderately elevated (quotient of valve II = 0.31), side slopes slightly concave, valves solid, beaked. Tegmentum densely granulated, girdle expanded anteriorly (Fig. 5 ).

Tegmentum ground colouration yellowish, dark orange at the valves edges and jugum, with mostly white pustules and irregular small green maculation; girdle yellow to orange with irregular brownish patches and white blotches around the tufts (Figs 5 , 6 ). Dorsum, despite well-defined jugum, hardly keeled, side slopes straight to slightly convex. Tegmentum densely covered with polymorphic pustules (Figs 6 , 7 A – E).

Head valve semicircular with rather straight posterior margin, notched in the middle, with five elevated ribs consisting of irregular, elongate pustules, larger towards anterior and side margins of the valve, pustules between the ribs smaller, roundish in the apical region and larger, more elongate towards the margins (Fig. 6 A, G, Fig. 7 A). Intermediate valves roughly rectangular, weakly produced forward at jugal part, the posterior edge of the valve having a central protrusion that extends outwards, creating a small beak, flanked by straight edges on either side (Fig. 6 C, Fig. 7 C). Jugal area with wavy ridges, wedge-shaped, separated from the lateropleural areas. Lateropleural areas moderately elevated with an inconspicuous diagonal ridge consisting of slightly elevated and larger pustules, separating areas with different kind of granulation: anterior part covered with sparsely distributed, small and oval pustules (Fig. 6 C, Fig. 7 B, C) and posterior part with densely arranged, much larger and irregular pustules (Fig. 6 C, Fig. 7 C, D). Tail valve small, almost circular, slightly wider than long, with antemedian flat mucro, straight postmucronal slope; seven inequidistance elevated ribs formed by elevated large pustules correspond to the articulamentum slits; granulation of the tail valve similar to the intermediate valves, with the antemucronal area covered with small oval pustules and the postmucronal area with densely distributed, much larger and elongate pustules (Fig. 6 E, H, Fig. 7 E).

Articulamentum strongly developed, creamy-pink, but white in apophyses and under the pleural areas of the intermediate valves. Slit formula: 5 / 1 / 7. Slits deep and wide, smooth, but with distinct dorsal grooves; insertion plates long and wide. Apophyses well-developed, rounded in a head valve, trapezoidal in valve II and very short, but wide, rectangular with rounded edges in tail valve (Fig. 6 B, D, F).

Girdle anteriorly expanded, light orange with irregular brownish patches and white blotches around the tufts. Dorsally densely covered with short, flattened spicules, with distinct radial ribs in their upper half – ribs usually not reaching the tip which tends to be tapered and smooth, L: 56–62 μm (mean = 58 μm, n = 10), W: 10–15 μm (mean = 12 μm, n = 10), intermingled with long, randomly, but densely distributed hair-like, smooth long spicules, usually bent, L: 210–420 μm (mean = 318 μm, n = 3), W: 33–42 μm (mean = 37 μm, n = 3) (Fig. 8 A – C); 18 sutural tufts indistinct, consisting of very short (likely broken), thick, straight spicules. Marginal fringe of elongate, rounded, straight and point-ended spicules (some spicules striated), L: 322–347 μm (mean = 340 μm, n = 3), W: 37–50 μm (mean = 42 μm, n = 3) (Fig. 8 D). Ventral spicules densely arranged, tiled, polymorphic, very elongate to oval with a clear zonation. The anterior and middle part of hyponotum covered with longitudinally densely striated, flattened scale-like spicules, L: 75–120 μm (mean = 87.6 μm, n = 7), W: 40–75 μm (mean = 53.4 μm, n = 7) (Fig. 9 A). The posterior part of hyponotum covered with elongate, flattened, sharply pointed or slightly tapered and deeply striated spicules, L: 170 μm, W: 30 μm, n = 1, (Fig. 9 B). Mantle fold with smooth, flat, elongated scales at the edges (L: 800 μm, W: 200 μm, n = 1) and very long, straight, deeply striated spicules, L: 451–553 μm (mean = 499 μm, n = 8), W: 21–44 μm (mean = 32.5 μm, n = 8), intermingled with similar, but much shorter spicules (up to 250 μm), more abundant closer to the interior part of the mantle fold (Fig. 9 C – F).

Radula of holotype small, ca. 3 mm in length, with 46 rows of teeth, of which 40 are matured. Central tooth subrectangular, the apical edge is very thin and folded, which gives it a bicuspid look, with wide base and tapering towards the top, the antero-lateral corner of the centro-lateral tooth is obtuse and smooth, thin. First lateral tooth elongate, major lateral tooth robust, with tricuspid head, denticles pointed, of similar size (Fig. 7 F).

Gills merobranchial, six ctenidia per side.

Type material

Holotype (MNHN-IM- 2019-34865) now partly disarticulated; parts of girdle and radula on two SEM stubs and the vial with the specimen stored in 96 % ethanol; and one paratype ( SMF 380885) stored in 96 % ethanol.

Material examined

Only known from the type material.

Type locality

Solomon Islands, NW San Cristobal, 10°17'S, 161°43'E, 97–223 m depth.

Diagnosis

Chitons of small size, up to 15 mm, body oval, girdle expanded anteriorly; colour of the tegmentum yellowish, mottled with dark orange and green; girdle yellow to orange with brownish maculation and white patches around the tufts. Valves carinated, moderately elevated, densely covered with pustules. Head valve with five distinct ribs, tail valve almost circular, mucro antemedian, flat. Perinotum covered with short, ribbed spicules and scattered with hair-like long spicules; hyponotum covered with scale-like, deeply striated spicules and very long thin spicules on the mantle fold.

Etymology

The specific epithet zefranki is a masculine adjective formed from the name of Hosea Jan "Ze” Frank, an online performance artist known for his wit, creativity and humorous approach to scientific knowledge in the YouTube series TRUE FACTS. The name honours his influential contributions to internet culture and the vision he has brought to the SENCKENBERG OCEAN SPECIES ALLIANCE as a member of its advisory board.

Distribution

At present known only from its type locality, the Solomon Islands.

Taxon discussion

Morphological discussion

The genus Craspedochiton consists of 14 currently accepted species and five of them belong to Thaumastochiton - group Thiele, 1909 ( Schwabe and Els 2019) which is characterised by the uplifted posterior mucro and unslitted callus in the tail valve. As Craspedochiton zefranki sp. nov. has antemedian positioned mucro, it surely does not belong to this group. The new species can be immediately distinguished from the rest of the species belonging to the same genus by its roundish insertion plates in the head valve (in all other species they are rectangular). Additionally, below there are provided more detailed differences between the new species and other Craspedochiton reported from the similar geographic range. C. zefranki sp. nov. differs from:

Craspedochiton elegans (Iredale & Hull, 1925) by sculpture of the valves (small, fine pustules in C. elegans vs. much larger, coarser pustules in C. zefranki sp. nov.), by the shape of the tail valve (rhomboidal in C. elegans vs. roundish in C. zefranki sp. nov.), position of the mucro (in posterior third and elevated in C. elegans vs. antemedian and flat mucro in C. zefranki sp. nov.);

Craspedochiton hystricosus Kaas, 1991 by the sculpture of the valves (much finer, smaller pustules, roundish or elongate vs. much larger, irregular, but squarish in C. zefranki sp. nov.), longitudinal ridges in the pleural area of the intermediate valves (present in C. hystricosus vs. absent in C. zefranki sp. nov.), position of mucro (more posteriorly located in C. hystricosus vs. antemedian in C. zefranki sp. nov.), ridges on the head valves (only weakly indicated in C. hystricosus vs. conspicuous in C. zefranki sp. nov.);

Craspedochiton jaubertensis Ashby, 1924 by the sculpture of the valves (much larger, solid pustules in C. jaubertensis vs. smaller, less coarse pustules in C. zefranki sp. nov.), the shape of the valves (median trapezoidal in C. jaubertensis vs. rectangular in C. zefranki sp. nov.), position of mucro (more central in C. jaubertensis vs. more anteriorly located in C. zefranki sp. nov.), apophyses in tail valve (longer, more produced forward in C. jaubertensis vs. shorter, reaching the postmucronal areas in C. zefranki sp. nov.);

Craspedochiton laqueatus (G. B. Sowerby II, 1842; Dell’Angelo et al. (2010) – illustrations of type material) by the sculpture (larger, coarser pustules, especially in the pleural areas of intermediate valves in C. laqueatus vs. smaller, more densely arranged pustules, rounded and small in pleural areas of intermediate valves in C. zefranki sp. nov.), by the shape of the second valve (convex anterior edge, protruding beak flanked by concave posterior edges in C. laqueatus vs. almost straight, slightly protruding at jugal part and a small beak flanked by straight posterior edges in C. zefranki sp. nov.), morphology of hyponotum scales (less numerous striae in C. laqueatus vs. much more numerous striae in C. zefranki sp. nov.);

Craspedochiton tesselatus Nierstrasz, 1905 by the shape of the apophyses in the head valve (rectangular in C. tesselatus vs. roundish in C. zefranki sp. nov.), position of mucro and postmucronal slope (median mucro and strongly concave slope in C. tesselatus vs. antemedian mucro and straight slope in C. zefranki sp. nov.).

Molecular discussion

The obtained sequence was positively checked as belonging to Polyplacophora against the GenBank database; however, with only ca. 86 % similarity to published sequences. The closest relative in GenBank was Acanthochitona ferreirai W. G. Lyons, 1988 (86.02 % similarity, acc. No. MK 016365.1). The number of publicly available sequences of Craspedochiton is relatively low (2 COI sequences belonging to two species). A phylogenetic analysis which could explain low similarity to the other sequences from the same genus was not conducted; the COI barcode of the new species is provided for future use.

Methods

Live animals were collected at depths of 97–223 m by the French expedition SOLOMON 1 at Station DW 1840 near the Solomon Islands. Specimens were fixed in 100 % ethanol. The systematic classification follows Sirenko (2006), the morphological nomenclature following Schwabe (2010).

For scanning electron microscopy (SEM), the valves and radula were removed, cleaned with a diluted bleach solution (1: 1 with H 2 O) and rinsed in distilled water. Several small pieces of dorsal and ventral girdle were sampled, as the spicules tend to be highly polymorphic at intra-individual level, following Schwabe and Els (2019) recommendations. Girdle tissue was only air dried. Objects were placed on SEM stubs using double-sided adhesive tabs. Samples were examined with a HITACHI TM 4000 tabletop SEM. After SEM examination, spicules which best represented variability of the species girdle were presented in the figures. All figures were assembled in Adobe Photoshop.

For DNA barcoding, a small fragment of tissue from the holotype’s foot 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 TaKaRa Taq HS Perfect Mix from TaKaRa. The PCR conditions involved an initial denaturation step at 94 ºC for 5 minutes; then 35 cycles of denaturation at 94 ºC for 45 seconds, annealing at 50 ºC for 45 seconds and extension at 72 ° C for 1 minute and 30 seconds; followed by a final extension step at 72 ° C for 5 minutes. The obtained sequence was manually inspected and trimmed to the length 612 bp in Geneious Prime v. 2023.1 and was made publicly available on GenBank under accession number PV 664593.

Specimen data for this description were (in parts) processed via the Discovery Laboratory of the SENCKENBERG OCEAN SPECIES ALLIANCE.

Abbreviations used in the text are as follows: Muséum National d'Histoire Naturelle, Paris, France ( MNHN); Senckenberg Research Institute and Natural History Museum Frankfurt ( SMF).

Repository: Holotype (MNHN-IM- 2019-34865) is now deposited in the collection of MNHN; one paratype ( SMF 380885, old MNHN number: MNHN-IM- 2019-35217) is deposited in the malacological collection of SMF.

Figures

Figure 5. Craspedochiton zefranki Vončina, sp. nov. A, B Holotype MNHN-IM- 2019-34865, dorsal and ventral view, respectively; C, D Paratype SMF 380885, dorsal and ventral view, respectively. Scale bar: 5 mm.

Figure 6. Craspedochiton zefranki Vončina, sp. nov., holotype MNHN-IM- 2019-34865. A, C, E Valves I, II, VIII, respectively, dorsal view; B, D, F Valves I, II, VIII, respectively, ventral view; G, H Valve I, VIII, respectively, lateral view. Scale bar: 250 μm.

Figure 7. Craspedochiton zefranki Vončina, sp. nov., holotype MNHN-IM- 2019-34865. A, C, E Valve I, II, VIII; B, D Details of tegmental surface of valve II in the anterior and posterior part of lateropleural area, respectively; F Central portion of radula. Scale bars: 2 mm (A, C, E), 500 µm (B, D), 200 µm (F).

Figure 8. Craspedochiton zefranki Vončina, sp. nov., holotype MNHN-IM- 2019-34865. A, B Dorsal girdle spicules from the anterior part of perinotum; C Dorsal girdle spicules and hair from the anterior part of perinotum; D Marginal spicules. Scale bars: (1) 200 µm (A), 100 µm (B), 300 µm (C, D).

Figure 9. Craspedochiton zefranki Vončina, sp. nov., holotype MNHN-IM- 2019-34865. A – F Ventral spicules. A Spicules of the central part of hyponotum; B Spicules of the posterior part of hyponotum; C Single spicule from the anterior part of the mantle fold; D, E Spicules from the central part of the mantle fold; F Spicules from the posterior part of the mantle fold. Scale bars: 300 µm (A, B) 400 µm (C), 200 µm (D, E, F).