Siphonaria scabra Reeve, 1856

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 : 84-86

Siphonaria scabra Reeve, 1856

( Figs 31L–N, P–Q, V–W , 32E–F )

Siphonaria scabra Reeve, 1856 : pl. 1, species 2 (type locality Port Jackson [Sydney Harbour], Australia).— Hanley 1858b: 152; Angas 1865: 190; Tenison Woods 1878b: 99; Paetel 1883: 178; Whitelegge 1889: 117; Hedley 1917a: 715, pl. 1, fig. 32; 1917b: M95; Galindo 1977: 416; McAlpine 1952: 41; Trew 1983: 7; White & Dayrat 2012: 67.

Siphonaria diemenensis var. scabra — Tenison Woods 1878b: 99; Hubendick 1945: 66; 1946: 38, pl. 2, fig. 14.

Material examined. Type material. Lectotype of Siphonaria scabra Reeve, 1856 , present designation, from Port Jackson , [Sydney], Australia ( NHMUK 1981011 /1, Fig. 31L ). Four paralectotypes, same data as lectotype ( NHMUK 1981011 /2-4, Figs 31P–Q ).

Other, non-type material. Australia, Qld: Slade Point, Mackay, 21°03.813’S, 149°13.527’E, Q14- 1 ( AM C.585702 8p, C.585139 d [M214], C.585140 p [M215], C.585141 p [M216]); Wreck Pt, Yeppoon, 23°08.736’S, 150°45.865’E, Q08-4 ( AM C.585138 p [M426]); Northwest Island , 23°17.683’S, 151°42.997’E, Q07-3 ( AM C.585130p [M078]); Urangan Hervey Bay , 25°17.504’S, 152°54.664’E, Q05-1 ( AM C.585342 p, C.585127 p [M403], C.585128 p [M182]); Drury Point Scarborough, 27°12.168’S, 153°06.980’E, Q03-8 ( AM C.585748 1 p); NSW: Bolton Point Lake Macquarie, 33°0.389’S, 151°36.889’E, NSW08-3 ( AM C.585448 12p, AM C.585060 p [SK168], AM C.585062 p [SK169]); Laings Point Sydney Harbour, 33°50.419’S, 151°16.638’E, NSW06-3 ( AM C.585898 7p, C.585061 p [M152], C.585114 p [M154]) .

Taxonomic remarks. The syntype marked as ‘type’ ( Fig. 31L ) is herein designated as the lectotype of S. scabra for the stabilisation of the name (Art. 74.1 of the Code). Our delineation of this species is based on comparative analyses of the morpho-anatomy and mitochondrial genetics of freshly collected topotypes ( Fig. 31J ) and geographic series of additional specimens (Table S1). Several authors treated S. scabra as a junior synonym or variety of S. diemenensis , which is rejected herein. The record of ‘ S. scabra ’ from SA in Adcock (1893: 11) is probably a misidentification of S. zelandica and incorrectly synonymised with S. luzonica .

External morphology. Foot sole, foot wall, foot edge, mantle and cephalic folds all evenly cream, paler at foot edge; regular vertical black pigmentation bands/ stripes on foot wall, short of foot edge; mantle narrow, strongly finely lobed, thickened at edge; pneumostomal lobe narrow, faint black pigmentation, under mantle behind right cephalic fold; closes the pneumostomal and anal openings at the mantle edge; two small black epithelial eye spots centralised on two centrally touching cephalic folds; genital pore inconspicuous, located on foot wall to right anterior of right cephalic fold.

Shell ( Figs 31L–N, P–Q, V–W ; Table S9). Medium sized (max sl mean = 16.1 mm, SD = 3.4 mm, n = 7), elongate ovate; height medium; apex offset sightly posterior and to left, apical sides convex, protoconch direction homostrophic (n = 3; Fig. 31V ), shell whorl dextral; exterior sculpture variable, uneven, rough, growth striae layered leaving rib protrusions, uneven; radial colour bands, protoconch dark, central pale, edge with dark rib interstices; shell thick; rib count (mean = 37, SD = 6.8, n = 7), with ten primary ribs ( Fig. 31N ), pale white to cream, wavy, broad, ridges flat to rounded, shell lip uneven ribs weakly protrude at shell edge; few (1–2) secondary ribs between and of similar width to primary ribs; rib interstices darker, width slightly less than rib width; siphonal ridge not prominent, formed by paired primary ribs. Interior shell margin dark chocolate brown with white rays under primary/secondary ribs extending to spatula, shell edge corrugated by rib ends, siphonal groove distinct; spatula dark chocolate brown, sometimes reddish, mottled to lighter tan; ADM scar distinct, deep, CMS straight.; thickening of shell lip occurs without whitening, infills and reduces lip scalloping; coarse and fine rib as well as prominent primary/secondary rib change ( Fig. 31N ).

Reproductive system ( Fig. 32E; n = 2): Positioned within coelom under the respiratory cavity, hermaphroditic glands positioned to posterior against right foot wall and over foot sole, epiphallic parts positioned to anterior between BM and RAM; merge of AO and GA indistinct, AO relatively large, elongated, bluntly pointed, twisted and centrally bent (without a prominent MA), slightly larger than GA, thicker than ED; ED relatively long, centrally bent, thick; EG white, folded, elongated; single flagellum F1 on EG, long, twisted, thickish; AO, GA and ED all muscular white tissue; BD and CD with opposing connections to GA between ED, AO and singular GP; BD long, heavily looped on anterior side with prominent MA, much longer than CD of similar thickness, both ducts smooth and pass together through RAM connecting into MG ( BD above CD), BC translucent, clear test, relatively large, bulbous, (0 to 1 SPM in BC’s of three specimens) ; HD with prominent brown markings, short, thickened, coiled, links AG to a small, elongated, narrow, brownish/ yellow spotted, finely granulated HG, inner edge firmly moulded; MG and AG small, folded, soft white tissue; purple SV embedded on left side of AG, AG larger than HG, sides match curvature of inner foot wall at right posterior quarter of coelom.

Spermatophore ( Fig. 32F ): Body cylindrical, thread-like (length = 10.88 mm, n = 1), test thin, translucent; head section, bluntly rounded, containing a white gelatinous core, tapers to a thin flagellum and tip; both sections smooth, featureless; head shorter, thicker than flagellum (head length = 10.03 mm; 92% of SPM length; flagellum length = 0.85 mm; head width = 93 μm; flagellum width = 13 μm). Single SPM tightly coiled in brown gelatinous mass in BC of topotypic specimen.

Comparative remarks. Siphonaria scabra ( atra group, unit 50) is the sister species of S. pravitas sp. nov. (unit 51); both species together form a well-differentiated and well-supported sub-clade ( Figs 1 , 2 ). They differ from each other by COI distances of ≥ 8.2% (Table S4). Siphonaria scabra differs from any other species by COI distances of ≥ 24% (Table S4). Throughout its range, S. scabra has been found in sympatry with nine congeners. Five congeners are sympatric in eastern Australia: For comparisons with S. normalis , S. atra , S. denticulata refer to comparative remarks under these species. Siphonaria opposita has a lower shell with a dual-ribbed siphonal ridge, a larger pointed AO, larger BC, and a shorter ED. Four species occur in sympatry with S. scabra in Sydney Harbour: For comparison with S. diemenensis and S. zelandica refer to comparative remarks under these species. Siphonaria funiculata has a taller shell with a dual ribbed but indistinct siphonal ridge, less raised ribbing and weaker edge scalloping, a shorter ED and AO, larger BC, and a shorter, drop-like SPM.

Siphonaria pravitas sp. nov. has a lower shell with stronger raised ribs and edge scalloping, a smaller AO, shorter ED, larger BC, a shorter wider BD with no distal loop, and a shorter SPM. Specimens figured as ‘ S. diemenensis var. scabra ’ from ‘Port Jackson [Sydney Harbour]) in Hubendick (1946: pl. 2, figs 14–15) are likely specimens of S. denticulata based on patterning on shell lip and margin and only possibly of S. scabra based on the presence of few secondary and even primary ribs, yet clearly not of S. diemenensis .

Distribution and habitat. Endemic to subtropical to temperate east coast of Australia ( Fig. 25 ). In this study found on sheltered rocky shores across upper to mid littoral levels.

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 2. Maximum Likelihood phylogram (partial, species not collapsed). Clades G–I (atra group) 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 (seeTables 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 spread over two pages.

FIGURE 25. Known occurrence records of S. viridis, S. normalis, S. radians, S. scabra, S. funiculata, S. kurracheensis and S. carbo.

FIGURE 31. Shells of S. normalis, S. radians and S. scabra. A–I, O, S–U. S. normalis, A. Hawaii, syntype USNM 15346. B. Maui, TS, AM C.585929 [M296, SK240]. C. Oahu, TS, AM C.585930 [SK209]. D. Probable holotype of P. soranus AM C.103709. E. Qld, Townsville, TS of P. soranus AM C.585932 [SK075]. F. Qld, Cape York Peninsula, AM C.584792 [M180]. G. Marquesas, Fatu Hiva, IM-2013-74897 [M570]. H. PNG, Riwo waters, IM-2013-15250 [M555]. I. PNG, Wonad Is, IM-2013-15280 [M563]. O. Probable paratype of P. soranus MV F13840, S. Protoconch, Maui, AM C.584892 [SK212]. T. Protoconch, Qld, Cape York, AM C.585178 [SK195]. U. Hawaii, in situ. J–K. S. radians. J. Indonesia, Riau Islands, Neotype ZRC.MOL.24912 [M519]. K. Malaysia, ZRC.MOL.24894 [M594, SK526]. L–N, P–R, V–W. S. scabra. L. Lectotype NHMUK 1981011/1. M. NSW, Sydney Harbour, TS, AM C.585061 [M152]. N. AM C.585114 [M154]. P–R. Paralectotypes NHMUK 1981011/2-4. V. NSW, in situ. W. Protoconch, AM C.585062 [SK169]. Unlabelled scale bars = 10 mm.

FIGURE 32. Reproductive morphology of S. normalis and S. scabra. A–D. S. normalis A–B. Hawaii, Oahu, TS, AM C.585930 [SK209]. C. Guam, Umatac Bay, AM C.584872 [M346, SK142]. D. Hawaii, Maui, TS, AM C.585929 [M296, SK240]. E–F. S. scabra, NSW, Sydney Harbour, TS, AM C.585114 [M154, SK236]. Scale bars = 1 mm.