Siphonaria obliquata Sowerby I 1825
Creators: name: Jenkins, Bruce
name: Köhler, Frank
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Siphonariida
Siphonariidae
Siphonaria
Siphonaria obliquata

description: Siphonaria obliquata Sowerby I, 1825
(Figs 14A–D, N, Q–R, 15F–H)
Siphonaria obliquata Sowerby I 1825: 32 (“Van Diemen’s Land” [Tasmania; in error]).— Reeve 1842: pl. 138, figs 4–5; Catlow & Reeve 1845: 100; Jay 1850: 104; Reeve 1856: species 12; Hanley 1858b: 152; Hutton 1873: 56; Paetel 1873: 117; 1875: 92; Hutton 1878a: 41; 1880: 36; 1883: 141, pl. 17, figs A–D; Paetel 1883: 178; 1889: 429; Suter 1904: 68; Iredale 1908: 408; Suter 1909a: 33; Moss 1908: 41, pl. 9, fig. 24; Cottrell 1911: 582; 1912: 374; Suter 1913: 599; Iredale 1915: 478; Oliver 1923: 498; Odhner 1924: 55; Bucknill 1924: 83, fig. 3, 15–15a; Finlay 1927: 442, 478; Hubendick 1943: 4; Galindo 1977: 416; Powell 1979: 293, pl. 54, figs 12–13; Jenkins 1983: 28; Raven & Bracegirdle 2010: 46; White & Dayrat 2012: 66.
Siphonaria scutellum Deshayes, 1841: 1, pl. 35.— Catlow & Reeve 1845: 100; Jay 1850: 104; Dall 1870: 39 (non Blainville); Hutton 1873: 55; 1880: 36; 1883: 114; Stearns 1894: 405, 430; Suter 1909a: 33; Hubendick 1946: 24; Galindo 1977: 416; White & Dayrat 2012: 68.
Kerguelenia obliquata — Mestayer 1920: 117, figs 1, 2.
Benhamina obliquata — Finlay 1927: 442, 478. Powell 1937: 86, 1939: 217; Hubendick 1945: 60, 66, figs 11, 14; Powell 1946: 91, pl. 13 fig. 16; Borland 1950: 385; Knox 1954: 874, 1955: 86; Powell 1955: 120; 1957a: 114, pl. 20, fig. 16; Marcus & Marcus 1960: 108; Morton & Miller 1968: 302, fig. 109; pl. 19, fig. 10, 10a; Powell 1979: 293, pl. 54, figs 12, 13; Trew 1983: 3; Russell & Phillips 2009: 579.
Siphonaria (Benhamina) obliquata — Thiele 1931: 472; Hubendick 1946: 24, pl.6, fig.1–3; Shikama 1964: pl. 2, fig. 10; Berry 1977: 204, 210, fig. 19.
Siphonaria scutella —Burch 1945: 16 (invalid; incorrect subsequent spelling of scutellum).
Siphonaria obiliquata Murty et al. 2013: 104 (invalid; incorrect subsequent spelling obliquata).
Materialexamined. Typematerial. Neotypeof Siphonaria obliquata Sowerby I, 1825, present designation, from near quarry, NZ, Dunedin, W side Blackhead, 41°30.34′S, 171°56.76′E; coll. K. Walton, 6 Dec. 2020 (NMNZ M.331450 [M515, SK421], Fig. 14A).
Five syntypes of S. scutellum Deshayes, 1841 from Chatham Islands (MNHN IM-2000-5117, Fig. 14C).
Other, non-type material. NZ, South Island: same data as neotype (NMNZ M. 331114 p); Gentle Annie Point, N of Mokihinui River Mouth, West Coast 45°55.78′S, 170°25.72′E KW20-103 (NMNZ M.331115 6p, p [M516, SK422]; Fig. 14B); between Buttler and Gray Rivers, W Coast, 41°43.8’S, 171°29.31’E, NZS01 (AM C.585927 p [SK394], C.585928 p [SK401]). Point Elizabeth, 42°24’S, 171°13’E (AM C265378) (Fig. 14D).
Taxonomic remarks. Siphonaria obliquata is the type species of Benhamina Finlay, 1926 by original designation. The original type material is considered lost as it could not be found at the NHMUK in 2020 (J. Ablett, pers. comm.). The neotype is designated herein to ensure an unambiguous identification of this species, to stabilize its nomenclature, and to designate a correct type locality (Art. 75.3 and 76.1 of the Code). Sowerby (1825: Appendix 7), originally stated the origin of this species to be “Van Diemen’s Land [Tasmania]”. However, this probably incorrect since Siphonaria obliquata has never been found in Tasmania or elsewhere in Australia. The type locality is corrected to South Island, NZ (see above for details). Our delineation of this species is based on comparative analyses of the morpho-anatomy and mitochondrial genetics of freshly collected topotypes of S. obliquata and of S. sculellum and geographic series of additional specimens (Tables S1–2).
Reeve (1856) correctly stated that S. obliquata occurs in NZ and that S. scutellum is its junior synonym. Stearns (1894: 405, 430) reversed the priority of both species when treating them as synonyms referencing “Carpenter’s Reeve-Cuming List’ (Stearns (1894: 405). He also incorrectly states the distribution to be Galapagos. This was subsequently followed by Dall (1870: 39), who incorrectly added occurrence on the “W coast [of S America] N of Panama ”. Hubendick (1946: 24) correctly treated S. scutellum as a synonym of S. obliquata, but incorrectly listed it as a synonym of S. australis (Hubendick 1946: 49). Burch (1945: 16) listed ‘ S. scutella Deshayes’ as a valid species from Galapagos, which is rejected herein.
External morphology (Fig. 14N). Animal extends beyond shell coverage; foot sole swollen smooth, foot wall, mantle, cephalic folds and pneumostomal lobe evenly pale grey/cream, paler at edge foot/wall; blotches of black pigmentation on centre of cephalic folds, faintly on foot wall; mantle narrower than width of foot wall, non-translucent, covers exposed inner shell lip, edge thickened, lobed, vertical bands of black pigmentation aligned with shell rib interstices; single genital pore distinct, located on foot wall to right anterior of right cephalic fold; two small black epithelial eye spots centralised on two centrally touching cephalic folds; pneumostomal lobe long under the mantle between the right ADMs.
Shell (Fig. 14A–D, R; Table S9). Large sized (max sl mean = 48.1 mm, SD = 8.9 mm, n = 24), elongate ovate; height low to medium, often with lateral profile of shell edge arched profile; apex offset weakly posterior and central (usually eroded), apical sides anteriorly strongly convex, posteriorly straight to concave; protoconch direction heterostrophic (n=2; Fig. 14R), shell whorl dextral; exterior uneven, growth striae prominent, concentric brown tonal bands prominent, shell thick (often> 2mm); apical rib count (mean = 57, SD = 10.2, n = 24), ribs pale white, ridges rounded, interstices darker brown; 20–25 primary ribs, adapical, slightly more prominent than interspersed finer secondary ribs, often bifurcate, curved, increasingly raised and broaden to shell lip, shell edge weakly corrugated; siphonal ridge often indistinct, formed by paired primary ribs, wide at shell edge. Interior smooth, shell lip brown to black with white rays corresponding under ribs, margin white to tan, ADM scar paler, siphonal groove apparent, shallow, same colour as shell edge; spatula tan to fawn, often with irregular brown to grey markings; ADM scar distinct, CMS straight to convex, paler than shell lip; thickening of shell lip translucent, infills and reduces lip scalloping, spatula becomes whitened. Shell lip tends to thicken in adult specimens.
The neotype (Fig. 14A). Shell (sl = 35.5, sw = 22.6, sh = 11.2 mm) elongate ovate, medium; thick, apex offset weakly to posterior and left, exterior uneven, mottled brown with radial banding, ~ 45 ribs, siphonal ridge not prominent, formed by non-adjacent dual ribs. Interior shell lip dark brown weakly corrugated with pale rays aligning under ribs, margin whitish tan, RS (Fig. 15F) and SPM (Fig. 15G). Neotype specimen [M515] grouped within unit 96 (S. obliquata).
Reproductive system (Figs 15F–H; n = 3). RS positioned within right side of coelom under the respiratory cavity, hermaphroditic glands positioned to posterior against right foot wall and over foot sole, epiphallic parts positioned between sides of BM and RAM; AO, GA and ED merged, very large rounded, tapered to ED; ED wide, short, bent at join to distinct EG, large rounded fold, with orange striated prostate, curved continuation at top of ED, flagellum (F1) indistinct, twisted; epiphallic parts all muscular tissue; CD and BD both wide, short, featureless, jointly connect into AO on under side, BD over CD (in RS of neotype, BD appears absent but is enclosed within side tissue of CD (Fig. 15F), pass between outer side of RAM and inner foot wall; BD significantly wider, slightly curved; CD twisted immediately prior to entering MG/AG complex close to BD; BC large rounded, positioned between footwall and AG, test thick, opaque, filled with orange-brown gelatinous mass; curved elongated SV embedded in AG close to top of BC; single large GP with lobes at end of GA; HD prominent, brownish, folded and heavily lobed, links AG to yellow-tan, finely granulated HG; MG and larger AG small folded soft white tissue, MG at anterior of AG, sides moulded to curvature of inner foot wall at right posterior quarter of coelom.
Spermatophore (Fig. 15G). Short elongate, test thin, featureless, translucent (length = 4.38 mm, n = 1), head bluntly pointed; flagellum short; both sections smooth, featureless, short clear webbing spans the bend at taper between head and flagellum; head much larger than flagellum (head length = 3.0 mm, n = 1, ~ 76 % length of SPM; head width = 790 μm; flagellum width = 96 μm); three SPM found in neotype BC ([M515]), 2 appear to be the white core remnants of larger SPM’s decomposing; while the shape / size is consistent, no test or flagellum present.
Radula and jaw. Dentition formula 68:1:68 (258 rows) and description of jaw in Hutton (1883: 141, as ‘ scutellum ’); see Cottrel (1911: 586, fig. 6) for a description, dentition formula“about64:1:64”(Hubendick 1946: 25).
Comparative remarks. Siphonaria obliquata (lateralis group, unit 96) represents the sister group of a clade formed by three species, S. tasmanica, S. lessonii, and S. funiculata (Figs 1, 4). From these species it differs by 16S distances of ≥ 7.6% (S. funiculata), ≥ 7.9% (S. lessonii), and ≥ 8.9% (S. tasmanica) (no COI sequences available).
Within the distributional range of S. obliquata, we found three sympatric congeners: Siphonaria australis and S. propria are sympatric on the South Island of NZ, and have smaller, more circular ovate shells, with more scalloped shell edges, prominent raised ribbing, wider HDs, smaller ephiphallic parts and BCs, and threadlike SPM. Siphonaria lateralis is sympatric on Auckland Island, NZ, and differs by having a much smaller, evenly brown, and fragile shell, a smaller BC, a larger, wider BD, and more bulbous SPM. Anatomically, the structure of RS resembles that of S. lateralis and S. tasmanica, S. funiculata, S. lessonii (Güller et al. 2015: 85, fig. 4) and S. fuegiensis (Güller et al. 2015: 92, fig. 9), all of which are relatively closely related.
Hutton (1883: 141, pl. 17, figs B–D) and Cottrel (1911: 587–590, figs 2–4, 6–7, pl. 29, fig. 3) described the anatomy of S. obliquata; radula and jaw, RS. The RS depicted herein corresponds well with the RS depicted in Hutton (1883: 141), Cottrell (1911: 590), and Hubendick (1945: 18, fig. 14), but also reveals some intraspecific variation (e.g., details of epiphallic parts, of HD and CD in Cottrel and width of CD = “spov” in latter). The SPM shown herein (Fig. 15G) corresponds well with that shown by Hubendick (1945: 14, fig. 11), reproduced by Berry (1977: 210, fig. 19). The egg mass has been described by Mestayer (1920: 171). Borland (1950: 385) described the distribution, behaviour and ecology of S. obliquata.
Distribution and habitat. Recorded from North and South Islands as well as Chatham, Stewart and Snares Islands, NZ, between latitudes of 34° S and 48° S (Fig. 16). In this study found to be common on exposed rocky intertidal shores in sheltered positions, such as crevices, vertical faces, mostly shaded from the midday and afternoon sun, across upper and mid littoral levels.
description: Published as part of Jenkins, Bruce & Köhler, Frank, 2024, Hidden in plain sight: Systematic review of Indo-West Pacific Siphonariidae uncovers extensive cryptic diversity based on comparative morphology and mitochondrial phylogenetics (Mollusca, Gastropoda), pp. 1-217 in Megataxa 13 (1) on pages 34-38, DOI: 10.11646/megataxa.13.1.1, http://zenodo.org/record/14984186