Siphonaria acmaeoides Pilsbry, 1894

Siphonaria acmaeoides Pilsbry, 1894 View in CoL

Siphonaria acmaeoides Pilsbry, 1894: Pilsbry 1894: 16; Pilsbry 1895: 6, pl. 6, figs. 19–22; Lee 1956: 79; Hirase 1941: 94, pl. 121, fig. 15; Kuroda and Habe 1952: 86 (cited from Jenkins and Köhler 2024); Azuma 1960: 62 (cited from Jenkins and Köhler (2024)); Baker 1964: 159 (cited from Jenkins and Köhler (2024)); Christiaens 1980 b: 466; White and Dayrat 2012: 60 [checklist]; Jenkins and Köhler 2024: 114, 115, figs. 43 A – D, M, N, 44 A – C. View in CoL

Siphonaria (Patellopsis) acmaeoides View in CoL : Hubendick 1945: 70, fig. 19 (cited from Jenkins and Köhler (2024 )); Hubendick 1946: 30, pl. 6, figs. 12–15; Habe and Kikuchi 1960: 64 (cited from Jenkins and Köhler (2024)); Kira 1962: 201, pl. 69, fig. 9 a, b (misspelled as ' Patellops '; cited from Jenkins and Köhler (2024)).

Siphonaria zebra View in CoL : Kuroda and Habe 1952: 86 (non Siphonaria zebra Reeve, 1856 View in CoL ) (cited from Jenkins and Köhler (2024)).

Planesiphon acmaeoides : Kuroda et al. 1971: 484, pl. 64, fig. 8; Choe 1992: 749, pl. 126, fig. 224.

Siphonaria (Mouretus) acmaeoides View in CoL : Christiaens 1980 a: 79, 80.

Siphonaria (Planesiphon) acmaeoides View in CoL : Inaba 1983: 149 (cited from Jenkins and Köhler (2024)); Je 1989: 29 [checklist]; Higo et al. 1999: 402, G 4976 [checklist]; Okutani 2000: 815, pl. 405, fig. 7; Cheng et al. 2005: 8, fig. 1 e – g; Noseworthy et al. 2007: 90 [checklist]; Okutani 2017: 1101, pl. 403, fig. 7.

Materials

Type status: Other material. Occurrence: catalogNumber: NIBRIV 0000307707 ; individualCount: 1; occurrenceID: 83FCD050-F70C-5128-B42F-DE6C1A9BA020; Taxon: scientificName: Siphonaria acmaeoides ; kingdom: Animalia; phylum: Mollusca; class: Gastropoda; order: Siphonariida ; family: Siphonariidae ; genus: Siphonaria ; specificEpithet: acmaeoides ; scientificNameAuthorship: Pilsbry, 1894; Location: country: Korea; locality: Hyeongjehaean-ro, Andeok-myeon, Seogwipo-si, Jeju-do ; verbatimCoordinates: 33°13'37.13"N 126°18'30.92"E; Event: eventDate: 2012-01-07 GoogleMaps

Type status: Other material. Occurrence: individualCount: 3; occurrenceID: D7664B8A-483D-5DD2-9933-CECE40648E65; Taxon: scientificName: Siphonaria acmaeoides ; kingdom: Animalia; phylum: Mollusca; class: Gastropoda; order: Siphonariida ; family: Siphonariidae ; genus: Siphonaria ; specificEpithet: acmaeoides ; scientificNameAuthorship: Pilsbry, 1894; Location: country: Korea; locality: Sagye-ro, Andeok-myeon, Seogwipo-si, Jeju-do ; verbatimCoordinates: 33°13'13.2"N 126°17'42.0"E; Event: eventDate: 2022-04-21 GoogleMaps

Type status: Other material. Occurrence: individualCount: 3; occurrenceID: A1D5EA8B-4851-5AD4-A0A1-2FCC3E1B0328; Taxon: scientificName: Siphonaria acmaeoides ; kingdom: Animalia; phylum: Mollusca; class: Gastropoda; order: Siphonariida ; family: Siphonariidae ; genus: Siphonaria ; specificEpithet: acmaeoides ; scientificNameAuthorship: Pilsbry, 1894; Location: country: Korea; locality: Donghaean-ro, Guryongpo-eup, Nam-gu, Pohang-si, Gyeongsangbuk-do ; verbatimCoordinates: 35°57'05.7"N 129°33'04.4"E; Event: eventDate: 2023-07-23 GoogleMaps

Type status: Other material. Occurrence: individualCount: 1; occurrenceID: 84F9DDD5-5BD5-5645-8D86-F3D843A9ACD2; Taxon: scientificName: Siphonaria acmaeoides ; kingdom: Animalia; phylum: Mollusca; class: Gastropoda; order: Siphonariida ; family: Siphonariidae ; genus: Siphonaria ; specificEpithet: acmaeoides ; scientificNameAuthorship: Pilsbry, 1894; Location: country: Korea; locality: Irun-myeon, Geoje-si, Gyeongsangnam-do ; verbatimCoordinates: 34°58'34.9"N 128°41'18.18"E; Event: eventDate: 2023-04-19 GoogleMaps

Description

Measurements: Shell length [SL] 11.32–17.58 mm, Shell width [SW] 9.42–14.87 mm, Shell height [SH] 2.63–6.73 mm.

Shell (Fig. 2 a View Figure 2 a , b View Figure 2 b ) solid, oval, small to medium in size (in examined specimens, SL 11.32–17.58 mm), medium-high in height (about 2 / 7 on its length). Exterior colour generally greyish-brown or yellowish-brown with dark brown irregular maculations. Shell surface with 14–17 wide, light-cream or white-coloured primary ribs, unevenly spaced, sometimes discontinuous from apex to outer shell margin in juvenile. Interspaces between primary ribs filled with 1–7 thin secondary ribs. Apex white, glossy, spiral in counterclockwise direction (Fig. 2 b View Figure 2 b C), often eroded due to shell growth, positioned in posterior one-third of shell, biased towards left. Shell margin weakly undulated. Anterior slope slightly convex, posterior slope short, nearly straight. Siphonal groove indistinct on outer shell surface. Interior colour dark brown, reddish-brown, with light cream bands near margin, reddish-brown or pale at centre.

Radula (Fig. 3 a View Figure 3 a , b View Figure 3 b ) dentition formulae 27: 1: 27 (in specimens measuring SL 16.23 mm, SW 11.88 mm, SH 4.80 mm). Each transverse row with narrow central rachidian tooth flanked by symmetrical half rows with lateral teeth, decreasing in size outwards. Rachidian tooth (Fig. 3 a View Figure 3 a ) short, approximately one-third length of lateral tooth, with sharply-pointed cusp. Innermost lateral teeth (first 7 lateral teeth), each tooth consisting of mesocone without ectocone; mesocone with bicuspid (Fig. 3 a View Figure 3 a ). Middle lateral teeth (following 5 lateral teeth), each tooth consisting of mesocone and ectocone; mesocone with bicuspid to blunt towards the outer margins; ectocone sharply pointed. Outermost lateral teeth (remaining 12 lateral teeth) consisting of endocone, ectocone and mesocone; mesocone subquadrate-shaped; endocone and ectocone short, sharply pointed (Fig. 3 b View Figure 3 b ).

Distribution

Korea, Japan and Taiwan.

Type locality: Japan; Boshiu island (Boso Peninsula).

Habitat: On rocky substrate in high intertidal zones, typically in shallow pools (Fig. 2 a View Figure 2 a A).

Taxon discussion

The Korean S. acmaeoides corresponds well with Pilsbry (1894) ' s original description. The external shell morphology is characterised by wide, low primary ribs with fine secondary ribs in the interspaces, a glossy spiral apex coiling counterclockwise and a weakly undulated shell margin. Christiaens (1980 a) described a new subspecies, S. acmaeoides paulae Christiaens, 1980 , from Hong Kong, distinguishing it by its finer, thinner, more elliptical, lighter-coloured shell. This subspecies was also noted to lack a marked central area and exhibit a more bulging siphon compared to S. acmaeoides reported from Japan. However, Jenkins and Köhler (2024) later synonymised S. a. paulae with the S. acmaeoides , citing the morphological similarity of the shell. Based on our examination of the Korean specimens (Fig. 2 b View Figure 2 b ), we did not observe the light-coloured shell characteristics described in S. a. paulae by Christiaens (1980 a). Further morphological and molecular analyses for S. a. paulae sampled from Hong Kong are necessary to confirm the taxonomic validity of this subspecies. In addition, S. acmaeoides has repeatedly been noted for its similarity in shell and radula morphology to S. zelandica Quoy and Gaimard, 1833 which is distributed in Australia ( Hubendick 1946, Dayrat et al. 2014, Jenkins and Köhler 2024). Both species share the following morphological characteristics: a homostrophic apex, broad primary ribs with fine secondary ribs and an innermost lateral tooth in the radula with a mesocone that lacks ectocone and endocone ( Quoy and Gaimard 1833, Pilsbry 1894, Jenkins 1983, Jenkins and Köhler 2024). Hubendick (1946) reported the radula formula of S. acmaeoides as 26: 1: 26, noting the absence of an ectocone on the lateral teeth. In this study, we observed a similar pattern of radula characters, with a radula formula of 27: 1: 27, also lacking an ectocone on the lateral teeth. This can be generally included within the documented range of intraspecific variation for the genus Siphonaria (e. g. in S. lessonii Blaninville, 1827 , the radula formula varies from 13: 1: 13 to 76: 1: 76; Hubendick (1946), Güller et al. (2016)). In shell morphology, S. acmaeoides is distinguished by having its less prominent, almost flat radial ribs and a more indistinct siphonal groove, whereas S. zelandica is characterised by relatively finer and dual radial ribs within the siphonal groove. In our phylogenetic tree, the two species form a sister clade with 95 % bootstrap support (Fig. 4 View Figure 4 ). The uncorrected p - distances between S. acmaeoides and S. zelandica range from 5.71 to 6.51 %, while S. sirius , the next closest related species shows a significantly higher genetic divergence (27.94 %) (Table 2 View Table 2 ). Thus, a taxonomic re-assessment of the two species is necessary to confirm their taxonomic validity.