Acanthochitona crinita (Pennant, 1777)

Voncina, Katarzyna, Mikkelsen, Nina Therese, Morrow, Christine, Ang, Rory & Sigwart, Julia D., 2023, Clarification of the taxonomic status of Acanthochitona discrepans (Brown, 1827) with new data for the North-East Atlantic Acanthochitona (Polyplacophora, Acanthochitonidae), Biodiversity Data Journal 11, pp. 109554-109554 : 109554

Acanthochitona crinita (Pennant, 1777)

Chiton crinitus : Pennant, 1777 - Pennant 1777: 71, pl. 36, Figs. 1, A1.

Chiton crinitus non Chiton crinitus : Sowerby II, 1840a - Sowerby II 1840a: figs 88-93; 1840b - Sowerby II 1840b: 2.

Chiton onyx : Spengler, 1797 - Spengler 1797: 95; Kaas, 1981 - Kaas 1981: 220, fig. 6.

Chiton onyx non Chiton onyx : Morch, 1870 - Mörch 1870: 113.

Chiton fascicularis Chiton fascicularis : Brown, 1827 - Brown 1827: pl. 35 fig. 8 (not fig. 5); 1844 - Brown 1844: 65, pl. 21 fig. 8 (not fig. 5); Sowerby II, 1840a - Sowerby II 1840a: figs. 87, 87a; 1840a - Sowerby II 1840b: 1; Sowerby II, 1859 - Sowerby II 1859, pl. 10, fig. 5; Forbes & Hanley, 1849 - Forbes and Hanley 1849: 393, pl. 59 fig. 5; Hanley, 1855 - Hanley 1855: 15; Jeffreys, 1865 - Jeffreys 1865: 211; 1869 - Jeffreys 1869: 197, pl. 55 fig. 3; et mult auct.

Chiton fascicularis non Chiton fascicularis : Linnaeus, 1767 - Linnaeus 1767.

Chiton fascicularis var. minor : Philippi, 1836 - Philippi 1836: 108.

Acanthochaetes vulgaris : Leach, 1852 - Leach 1852: 229, pl. 10 fig. 8.

Chiton fascicularis var. attenuata : Jeffreys, 1865 - Jeffreys 1865: 212.

Acanthochites aeneus : di Monterosato, 1878a - di Monterosato 1878: 147.

Acanthochites aeneus non Acanthochites aeneus : Risso, 1826 - Risso 1826.

Acanthochites (ton) Acanthochites adansoni : de Rochebrune, 1881a - de Rochebrune 1881a: 44; 1881b - de Rochebrune 1881b: 116; 1881c - de Rochebrune 1881c: 238, pl. 17 figs. 9a-b; Pilsbry, 1893 - Pilsbry 1893: 13, pl. 8 figs. 33-34; Thiele, 1909 - Thiele 1909: 43, pl. 5 figs. 69-73; Bergenhayn, 1931 - Bergenhayn 1931: 28, pl. 3 fig. 81; Leloup, 1968 - Leloup 1968: 61, figs. 3-7, 11, 14.

Acanthochites (tori) Acanthochites bouvieri : de Rochebrune, 1881a - de Rochebrune 1881a: 45; 1881b - de Rochebrune 1881b: 117; 1881c - de Rochebrune 1881c: 239, pls. 17 figs. 10a, b; Pilsbry, 1893 - Pilsbry 1893: 13, pl. 3 figs. 65-66; Thiele, 1909 - Thiele 1909: 42; Leloup, 1968 - Leloup 1968: 62, figs. 4-7, 14.

Anisochiton (Acanthochites) fascicularis var. violacea : Pallary, 1902 - Pallary 1902: 29.

Acanthochites fascicularis vars var. Acanthochites fascicularis lutescens , Acanthochites fascicularis cinnabrina et Acanthochites fascicularis fusca : Dautzenberg & Durouchoux, 1906 - Dautzenberg and Durouchoux 1906: 15.

Acanthochitona crinitus : Winckworth, 1926 - Winckworth 1926: 15; 1932: 218.

Acanthochiton fascicularis : Leloup, 1936 - Leloup 1936: 3, fig. 3; 1968 - Leloup 1968: 60, figs. 1-6, 8-11, 13-14 (bibliography); et mult. auct.

Chiton fascicularis non Chiton fascicularis : Linnaeus, 1767 - Linnaeus 1767.

Acanthochiton gracilis : Leloup, 1968 - Leloup 1968: 74 (ex parte).

Chiton gracilis non Chiton gracilis Jeffreys, 1859 - Jeffreys 1859.

Acanthochitona crinita : Kaas, 1985 - Kaas 1985: 588, Figs. 7-50.

Acanthochitona crinita Type material. Neotype: RSMNH 1978.052.02601, Royal Scottish Museum of Natural History, Edinburgh, Scotland. Designated by Kaas (1985) (material not seen).

Acanthochitona crinita Type locality. Scotland, sea near Aberdeen ( Pennant 1777); Scotland, Monach Islands, North Uist, 57°31.5'N, 07°38.5'W ( Kaas 1985).

Materials

Type status: Other material. Occurrence : individualID: SMF 373026; individualCount: 1; lifeStage: adult; otherCatalogNumbers: BOLD:AAY5203, NIB_CCM_0542; associatedSequences: BOLD:CCMMO049-21, GenBank : OR526579 ; occurrenceID: F0AAA8D3-4C51-551B-95F3-0C69454D56D4; Taxon : scientificNameID: Acanthochitona crinita; Location: country: England; locality: Falmouth ; verbatimCoordinates: 50°08'38"N 5°03'46"W; Event: eventDate: 08/10/2021; eventRemarks: Rory Ang and Jessie Dermody leg.; Record Level: collectionCode: Malakologie- SMF; basisOfRecord: PreservedSpecimen Type status: Other material. Occurrence: individualID: SMF 363941-3; individualCount: 1; lifeStage: adult; associatedSequences: GenBank: OR145408 ; occurrenceID: 602565CB-D2C4-5C78-85DB-C21D0702B889; Taxon : scientificNameID: Acanthochitona crinita; Location : country: Portugal; stateProvince: Azores; county: Sao Miguel ; locality: Ponta Delgada , Rosto do Cao ; verbatimCoordinates: 37°44.567'N 25°38.167'W; Event: eventDate: 29/07/2013; eventRemarks: Julia Sigwart, Laura Sumner-Rooney & Nicholas Carey leg.; Record Level: collectionCode: Malakologie- SMF; basisOfRecord: PreservedSpecimen Type status: Other material. Occurrence: individualID: SMF 363942-1; individualCount: 1; lifeStage: adult; associatedSequences: GenBank: OR145404 ; occurrenceID: F1F6B54D-AC5D-5102-97A0-B0BF71B35A28; Taxon : scientificNameID: Acanthochitona crinita; Location : country: Portugal; stateProvince: Azores; county: Sao Miguel ; locality: Capelas , Sao Vicente ; verbatimCoordinates: 37°50.4'N 25°40.8'W; Event: eventDate: 28/07/2013; eventRemarks: Julia Sigwart, Laura Sumner-Rooney & Nicholas Carey leg.; Record Level: collectionCode: Malakologie- SMF; basisOfRecord: PreservedSpecimen Type status: Other material. Occurrence: individualID: SMF 363942-2; individualCount: 1; lifeStage: adult; associatedSequences: GenBank: OR145405 ; occurrenceID: FDAF4402-13F8-5CCB-A272-A493FA0D2FD3; Taxon : scientificNameID: Acanthochitona crinita; Location : country: Portugal; stateProvince: Azores; county: Sao Miguel ; locality: Capelas , Sao Vicente ; verbatimCoordinates: 37°50.4'N 25°40.8'W; Event: eventDate: 28/07/2013; eventRemarks: Julia Sigwart, Laura Sumner-Rooney & Nicholas Carey leg.; Record Level: collectionCode: Malakologie- SMF; basisOfRecord: PreservedSpecimen Type status: Other material. Occurrence: individualID: SMF 363941-1; individualCount: 1; lifeStage: adult; associatedSequences: GenBank: OR145406 ; occurrenceID: 4863948B-0D53-5E02-B0C1-5AEFBCACC547; Taxon : scientificNameID: Acanthochitona crinita; Location : country: Portugal; stateProvince: Azores; county: Sao Miguel ; locality: Ponta Delgada , Rosto do Cao ; verbatimCoordinates: 37°44.567'N 25°38.167'W; Event: eventDate: 29/07/2013; eventRemarks: Julia Sigwart, Laura Sumner-Rooney & Nicholas Carey leg.; Record Level: collectionCode: Malakologie- SMF; basisOfRecord: PreservedSpecimen Type status: Other material. Occurrence : individualID: SMF 363943; individualCount: 1; lifeStage: adult; associatedSequences: GenBank : OR145403 ; occurrenceID: 4C33B9E9-B6CD-502D-80B1-E3E99435E35A; Taxon : scientificNameID: Acanthochitona crinita; Location : country: Portugal, Ilha de São Miguel, Ponta Delgada, Rosto do Cão; stateProvince: Azores ; county: Sao Miguel ; locality: Ponta Delgada, Rosto do Cao ; verbatimCoordinates: 37°44.567'N 25°38.167'W; Event: eventDate: 29/07/2013; eventRemarks: Julia Sigwart, Laura Sumner-Rooney & Nicholas Carey leg.; Record Level: collectionCode: Malakologie- SMF; basisOfRecord: PreservedSpecimen Type status: Other material. Occurrence: individualID: SMF 363941-2; individualCount: 1; lifeStage: adult; associatedSequences: GenBank: OR145407 ; occurrenceID: B71A3E64-B60E-5247-8F90-D598F186FD1B; Taxon : scientificNameID: Acanthochitona crinita; Location : country: Portugal; stateProvince: Azores; county: Sao Miguel ; locality: Ponta Delgada , Rosto do Cao ; verbatimCoordinates: 37°44.567'N 25°38.167'W; Event: eventDate: 29/07/2013; eventRemarks: Julia Sigwart, Laura Sumner-Rooney & Nicholas Carey leg.; Record Level: collectionCode: Malakologie- SMF; basisOfRecord: PreservedSpecimen Type status: Other material. Occurrence: individualID: ZSM20150336; individualCount: 1; lifeStage: adult; associatedSequences: GenBank: OR145411 ; occurrenceID: F70C7D1C-8366-5231-AEAC-95AB7AF1AC1E; Taxon : scientificNameID: Acanthochitona crinita; Location : country: France; stateProvince: Brittany, Finistère; locality: Roscoff ; verbatimCoordinates: 48°43'40''N 3°59'21''W; Event: eventDate: 10/06/2013; eventRemarks: Gerhard Haszprunar leg.; Record Level: institutionCode: SNSB-ZSM; collectionCode: ZSM-Mol; basisOfRecord: PreservedSpecimen

Description

(See Jones and Baxter (1987), Dell’Angelo and Smriglio (2001), Bonfitto et al. (2011), Mitov (2015), Schmidt-Petersen et al. (2015) for additional descriptions that pertain to A. crinita s.s.). Small to medium-sized (in examined material, BL: 8-18 mm, BW: 4-10 mm, BL/BW ratio: 2), outline oval, moderately elevated, semi-carinated, slightly protruding apices; girdle wide, spiculose. Tegmentum colouration not uniform, mottled and very variable (Fig. 1 A-B).

Head valve slightly wider than long, almost semicircular, five rays barely raised, apex clearly visible (Fig. 2 A). Intermediate valves ellipsoidal, wide, anterior margin slightly convex at both sides of straight or little concave jugum; hardly raised striated jugal area (Fig. 1 A-B, Fig. 2 B-C). Tail valve roughly semicircular with central, slightly elevated mucro (Fig. 2 E).

Tegmentum covered with densely packed to widely separated (density from 23 to 38 granules per 1 mm2, mean = 31, n = 8 specimens) granules of variable shape, from oval to more or less elongate drop-shaped; granules raised, flat-topped, with one macroaesthete subcentral surrounded by 8-16 posteromedially located microaesthetes (Fig. 1 A, Fig. 2 A-C, E, Fig. 3 B and Fig. 4 A).

Articulamentum thick, apophyses large, broadly rectangular, rounded at anterolateral margins, separated by a wide sinus; insertion plates wide, continuous with apophyses, slits moderately deep (slit formula: 5/1/2) (Fig. 2 ).

Girdle wide, fleshy, usually brighter than tegmentum, deeply encroaching sutural areas. Highly variable colour of the tegmentum and perinotum; usually from creamy-white to olive-green and brown, with different degrees of blotches in which white, yellow and brown variously combined; in some specimens, colours can be very bright, for example, bright yellow and orange. (Fig. 1 A-B). Perinotum covered with two kinds of spicules: evenly distributed, short, somewhat bent and distally striated spicules (up to 100 x 15 µm) and longer thick spicules (up to 260 x 40 µm), striated (some of them smooth), usually slightly curved, randomly interspersed amongst them (Fig. 3 D). Perinotum ornamentation highly variable, observed variability in examined specimens: dorsal ornamentation just as described above or only short and densely arranged spicules or densely arranged, short but very thin, irregularly-curved spicules, with long and thick spicules interspersed amongst them. Sutural tufts with around 20-46 thick, smooth needles (up to 340 x 20 µm) intermingled with much shorter and thinner needles (Fig. 3 C). Marginal fringe with long and finely-ribbed spicules (some spicules may have deep grooves); hyponotum beset with slightly flattened, distally finely striated spicules, similar to the short dorsal spicules, up to 110 x 18 µm (Fig. 3 E).

Radula central tooth elongated, almost straight at the top and slightly keeled near base; first lateral tooth wing-shaped and smaller than the central; second (major) lateral elongated, with accessory plate tricuspidate, outer denticle slightly shorter than the others; cusps pointed (Fig. 3 A).

Gills merobranchial, 13-15 ctenidia on each side.

Diagnosis

Acanthochitona crinita is well known for its high variability of morphological features. However, it can be distinguished from other NE Atlantic relatives on the basis of the below-mentioned morphological characters. A. crinita can be distinguished from A. discrepans (Brown, 1827), based on the number, size and arrangement of aesthetes on tegmental granules (one macroaesthete subcentral surrounded by larger, posteromedially-located 8-16 microaesthetes in A. crinita vs. 1-2 macroaesthetes: a single macroaesthete located in posterior third, second, if present, located centrally, surrounded by very small, posteriomedially located 26-40 microaesthetes in A. discrepans ), dorsal spicules (longer, thicker spicules up to 100 x 15 µm in A. crinita vs. smaller, thinner spicules up to 68 x 7.5 µm in A. discrepans ), tuft needles (longer spicules up to 340 x 20 µm, surrounded by a smaller number of very short and thin needles in A. crinita vs. longer spicules up to 1000 µm x 60 µm, surrounded by a large number of somewhat shorter and much thinner needles in A. discrepans ). A. crinita differs from A. fascicularis (Linnaeus, 1767) by the shape of the intermediate valves (ellipsoidal in A. crinita vs. triangular in A. fascicularis ), jugal area (hardly raised, not sharply separated from the latero-pleural areas in A. crinita vs. raised, sharply separated from the latero-pleural areas in A. fascicularis ), shape of dorsal granules (moderately to widely apart, oval to elongated oval in A. crinita vs. small, round, densely packed granules with the incision in the middle in A. fascicularis ), density of tegmental granules (23-38 granules per 1 mm2, mean = 31 in A. crinita vs. 42-70 granules per 1 mm2, mean = 52 in A. fascicularis ), number of microaesthetes (8-16 microaesthetes in A. crinita vs. 0-6 microaesthetes in A. fascicularis ), number of bristles in the sutural tufts (20-46 in A. crinita vs. 55-120 in A. fascicularis ). It differs from A. oblonga Leloup, 1981 by the shape of dorsal granules (moderately apart, oval to elongated oval in A. crinita vs. widely apart and very much elongated in A. oblonga ), number and arrangement of microaesthetes (8-16 microaesthetes located posteromedially in A. crinita vs. 6-9 microaesthetes, located mainly in the central area in A. oblonga ). It can be easily distinguished from A. pilosa Schmidt-Petersen, Schwabe et Haszprunar, 2015 by the shape of the IV valve (valve with the hind margin concave at both sides of the pronounced apex in A. crinita vs. valve with triangular posterior margin with no apex in A. pilosa ), density of tegmental granules (moderately to widely apart in A. crinita vs. densely packed in A. pilosa ), size of microaesthetes on the tegmental granules (bigger microaesthetes in A. crinita vs. smaller, ca. ½ of the diameter, in A. pilosa ), large dorsal spicules (not always present, sparse, curved spicules of size up to 260 x 40 µm in A. crinita vs. always present, dense and straight spicules of size up to 320 × 60-62 µm in A. pilosa ).

Distribution

Acanthochitona crinita is a widely distributed species in North-East Atlantic. The species inhabits the seas from of north of Scotland (locus typicus), south of England (molecular data and SEM photos from this study), north of France and Spain, west coast of Portugal (molecular data from GenBank), the Azores (molecular data and SEM photos from this study) and, most likely, the Mediterranean Sea (literature data).

Figures

Figure 1. Images of the adult specimens of Acanthochitona, dorsal view. A A. crinita from England, BL not measured; B A. crinita from the Azores, BL not measured; C A. discrepans from Norway, BL 17 mm; D A. fascicularis from Ireland, BL 23 mm; E A. fascicularis from the Azores, BL 13 mm.

Figure 2. Acanthochitona crinita from the Azores (A, C, E) and England (B, D). A Valve I, dorsal view; B Valve VI, dorsal view; C Valve VII, dorsal view; D Valve VII, ventral view; E Valve VIII, dorsal view.

Figure 3. Acanthochitona crinita from the Azores (A, D, E) and England (B, C). A Radula; B Valve VI, details of the tegmentum in the lateropleural area; C One of the 18 tufts of spicules on the girdle; D, E Tuft, dorsal and marginal spicules.

Figure 4. Morphology of the granules of tegmentum with the macro- and microaesthetes. A Acanthochitona crinita; B A. discrepans; C A. fascicularis.