Siphonaria oblia ( Jenkins, 2018 )

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), Megataxa 13 (1), pp. 1-217 : 140-141

Siphonaria oblia ( Jenkins, 2018)

( Figs 52J–L, O–P )

Pugillaria oblia Jenkins 2018: 281 , figs 3C–E, 4E–H, 6A–J (type locality: Hospital Point , Thursday Island , Torres Strait, Qld [ Australia]).

Material examined. Type material. Holotype of S. oblia from Hospital Point , Thursday Island , Torres Strait, Qld, 10°35.318’S 142°12.573’E;coll. Ponder and Loch, 29 Jun. 1976, on moderately exposed rocky reef ( AM C.125603 , figured in Jenkins 2018: fig. 6), 15 paratypes, same data as holotype ( AM C.125604 11p, 4d).

Other, non-type material. Australia, Qld: Torres Strait: N end Prince of Wales Island, beach opposite Hospital Point , Thursday Island , 10°35.748′S, 142°12.280′E ( AM C.265974 8d); S side of Thursday Island , 10°35.133′S, 142°13.257′E ( AM C.532862 8p); Wednesday Island , 10°31.0′S, 142°17.0′E ( AM C.265909 20+d); Bampfield Point, W side of Prince of Wales Island , 10°43.043′S, 142°6.833′E ( AM C.532863 9p; AM C.532864 10+p); Cape York Peninsula: Albany Passage, 10°44.278′S, 142°35.758′E ( AM C.265907 d); Mutee Head, 10°54.682’S, 142°15.204’E, Q50-2 ( AM C.585755 p [M105]); Somerset, S side of Fly Point, 10°45.195′S, 142°36.292′E, Q47-1 ( AM C.265910 8p, 6d; C.584902 p [M042]); Captain Billy Landing, 11°38.019′S, 142°51.472′E, Q46-1 ( AM C.559470 2p); Portland Road, 12°35.588′S, 143°24.660′E, Q45-1 ( AM C.559471 p); Point S of Bathurst Head, 14°17.583′S, 144°11.845′E, Q41-1 ( AM C.559473 10p); Lizard Island , Casuarina Beach, 14°40.447′S, 145°26.703′E, Q40-1 ( AM C.266052 d), 14°40.908′S, 145°27.007′E ( AM C.559473 3p); Point Archer, 15°35.558′S, 145°19.788′E ( AM C.49513 5d); Cape Kimberley, 16°16.535’S, 145°28.737’E, Q35-1 ( AM C.585478 17p, C.585172 p [M076], C.585505 p [SK392]); Port Douglas , 4 Mile Beach, 16°30.470′S, 145°28.168′E ( AM C.265953 d), 16°29.468′S, 145°28.425′E ( AM C.265908 2d); Pebbly Beach, Yule Reef, Trinity Bay , 16°35.031’S, 145°30.823’E, Q32-2 ( AM C.608188 2p); Red Cliff Pt N of Cairns 16°41.294’S, 145°35.080’E, Q33- 3 N of Cairns , Buchan Point , 16°44.172′S, 145°39.973′E ( AM C.265951 7d) .

Taxonomic remarks. Our delineation of this species is based on comparative analyses of the morpho-anatomy and mitochondrial genetics of freshly collected topotypes ( Figs 52J–L ) and a geographic series of additional specimens (Table S1).

External morphology ( Fig. 52O ). Animal tissue translucent; foot sole and foot wall evenly pale grey to cream; mantle thin, translucent with large whitish subepithelial pustules in thickened fringe, positioned along top edge of foot wall, forming a broad flat band, radial markings on mantle aligned with shell colour bands; foot wall narrow; faint brown/red splotches present on lower foot wall around body but not extending under mantle; pneumostomal lobe on right side narrow translucent with pointed lobe, covering inconspicuous anus in foot wall; brown markings on posterior lobe of pneumostomal lobe; two black ‘Eye’ spots prominent centrally on thickened cephalic lobes, centrally touching and marked with brown/ reddish splotches; genital pore inconspicuous, positioned in foot wall posterior to right cephalic fold.

Shell ( Figs 52J–L ; Table S9). Small sized (max sl <5 mm), ovate, height medium; centrally broad, thickness thin, maybe glassy translucent; apex well offset to posterior edge and left of centre line, apex below shell height, dorsally dark tan/brown in colour; offset growth reflected in apical ridge; protoconch direction weakly heterostrophic (n = 1; Jenkins 2018: 282, fig. 6J), shell whorl dextral; anterior and lateral apical sides convex, posterior weakly concave; apex ribs radiate from apex to shell lip, flat unraised, appear as bands, tan in colour, rib count (mean = 35, SD = 3.7, n = 32); siphonal ribs not prominent on exterior, apical cream banding of rib interstices prominent, colour bands widen slightly over lower half of sides to lip; number of apical bands varies within individuals, lip fragile, unscalloped, even; growth striae irregular, prominent; light periostracum covers lower parts of exterior sides, often freely extending; spatula glossy, brown, interior colouration reflects exterior colouration through translucent shell; ADM scar horseshoe-shaped, weakly indented shallow; cephalic ADM scar straight to weakly convex, between left and right rounded ADM scars; siphonal groove very weakly indented.

Reproductive system ( Jenkins 2018: 278, fig. 3C–D). Located in posterior region of coelom and partly covered by pallial cavity and digestive gland; HG granulated; MG and AG folded; a thickened weakly coiled brown-coated HD emerges from HG; small rounded SV enveloped within AG folds; CD emerges from base of AG folds, progressively decreasing in diameter anteriorly and narrowing to open in rear of GA, AO indistinct; bulbous EG and narrow elongate ED are located between BM and RAM; ED slightly coiled prior to entering GA close to single GP; what appear to be two prominent flagellum both close to join of ED and EG, one broad and blunt, other narrow and elongate ( Jenkins 2018: fig. 3B–C); BC pale brown bulbous with a thin translucent test, located beside posterior RAM; BC may appear deflated when without SPM ( Jenkins 2018: fig. 3B); elongate thickened BD leads from BC and, coupled with anterior section of CD, passes through RAM; both ducts enter separately into GA and opposite to entry of ED.

Spermatophore ( Jenkins 2018: fig. 4E). Over half length comprises a translucent cylindrical head section, tip bluntly rounded; flagellum very thin, transparent, tapering to a thread-like end; both sections smooth, featureless (length = 0.49 mm; head length = 0.19 mm, ~ 38 % of SPM length, head width = 17 μm, flagellum width = 4 μm, n = 1). Two SPMs coiled, embedded in a white gelatinous mass in BC of one paratype ( AM C.125604) .

Radula ( Jenkins 2018: 284, fig. 3E–G, 4E, F). Each half row has around six mid and nine outer lateral teeth; central tooth with single pointed mesocone, about one-third base length; inner laterals (i.e., without ecto/ endocones) absent; first mid lateral has prominent bicuspidate pointed mesocone, other mid laterals possess single cusped elongate mesocone, single cusped ectocones offset from side of mesocone; central tooth basal plate as long as adjacent mid-lateral teeth; mid-lateral teeth possess a single outward pointing forked prong and notch, rows interlock via these basal forks and notches; outer lateral teeth distinctly different in shape to mid laterals, teeth block-like with single cusped chisel-like mesocone, all possess a pointed endocone; starting around laterals 8–9 the number of ectocones is doubled on outer teeth, endocones and ectocones appear as separate cones, are variably-shaped, bluntly pointed, some almost as large as the mesocone. Dentition formula 15:1:15 +/−1 (n = 3; row count was not assessed).

Jaw ( Jenkins 2018: 283, fig. 4H). Located inside front of buccal cavity, orange-brown, arch shaped with unevenly ‘shingle’-arranged cone-like rods, ~ 80 rods wide (~ 0.8 mm) by ~ 9–10 rods deep (length = 27 μm, width = 8 μm, n = 12); tip bluntly rounded.

Comparative remarks. Genetically S. oblia ( normalis group, unit 77) is a well-differentiated lineage ( Figs 1 , 4 ). It differs from other species by COI distances of ≥ 15.6% (Table S8). In N Qld, this species has been found in sympatry with five congeners: For comparisons with S. viridisS. atra , and S. normalis refer to comparative remarks under these species. Siphonaria jiigurruensis sp. nov. has a larger, taller, paler shell with greater edge scalloping, a larger AO, longer ED, and a smaller BC. The combined shell geometry, size, and colouration of S. oblia is highly distinctive.

Distribution and habitat. Endemic to tropical NE coast of Australia, Qld, from Torres Strait to just N of Cairns ( Fig. 51 ). In this study, found on moderately exposed rocky intertidal marine shores in sheltered positions (e.g., on under-surface of rocks, amongst oysters, amongst fringes of coralline algae and in crevices), upper and mid littoral levels ( Fig. 52P ).

Figures

FIGURE 1. Maximum Likelihood phylogram based on analyses of a concatenated sequence data set of 16S and COI. Branches are collapsed at the species level. Branch labels give unit numbers and accepted species names. Numbers on branches indicate branch support employing 10,000 ultrafast bootstraps.Available genus-group names are shown next to their type species. Scale bar indicating modelled sequence divergence.

FIGURE 4. Maximum Likelihood phylogram (partial, species not collapsed). Clades C–F (normalis, lateralis and pectinata groups) of the tree shown in Fig. 1. Branch labels give specimen identifiers for new sequences or Genbank accession numbers for imported sequences from other studies and geographic regions (see Tables S1–S2 for details). Identical haplotypes are merged into single tips. Numbers on branches indicate branch support by employing 10,000 ultrafast bootstraps. Clade names give unit numbers and accepted species names. Scale bar indicating modelled sequence divergence.

FIGURE 51. Known occurrence records of S. alba, S. asghar, S. propria, S. jeanae, S. emergens, S. oblia and S. campestra sp. nov.

FIGURE 52. Shells of S. propria, S. jeanae, S. emergens and S. oblia. A–D, M–N. S. propria. A. Holotype NMNZ M.77363. B–N. NZ, N Island, NMNZ M.331452. B. [M509]. C. [M510]. D. [M511]. M. Protoconch [M514]. N. In situ. E–F, T. S. emergens. E. Holotype AM C.532860. F. Paratype AM C.265919. T. Protoconch, AM C.265919. G–I, Q–S. S. jeanae. G. Holotype AM C.123712. H. Vic, Point Lonsdale, AM C.585288 [M102]. I. WA¸ Point Dalling, AM C.585312 [M130]. Q. Protoconch, AM C.585213 [SK012]. R. WA¸ Point Dalling, in situ. S. WA¸ Point Dalling, animal. J–L, O–P. S. oblia, J. Qld, AM C.585755 [M105]. K. Qld, Cape York, AM C.584902 [M042]. L. Qld, Cape Kimberley, AM C.585505 [SK392]. O–P. Qld, Cape Kimberley, animals, in situ. Unlabelled scale bars = 10 mm.