Siphonaria alba Hubendick, 1943

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 : 130-133

Siphonaria alba Hubendick, 1943

( Figs 49D–G, U–V , 50E–F )

Siphonaria ferruginea — Smith 1909: 369; 1911: 315; Tomlin 1934: 82; Tan & Low 2014: 367 (not S. ferruginea Reeve, 1856 ).

Siphonaria alba Hubendick 1943: 2 , figs 3a, b, 7, 10, 11, 13 (type locality: Nordwatcher Javasee [near Singapore, Java Sea]). Morrison 1972: 57; Christiaens 1980a: 78; White & Dayrat 2012: 60.

Triellsiphon acervus — Hubendick 1945: 29 (not Triellsiphon acervus Iredale, 1940 ).

Siphonaria (Siphonaria) alba — Hubendick 1945: 72.

Siphonaria (Siphonaria) acervus — Hubendick 1946: 46, pl. 3, figs 10–12 (not S. acervus ( Iredale, 1940)) .

Siphonaria (Siphonaria) atra — Hubendick 1946: 52, pl. 4, figs 5–7 (not S. atra Quoy & Gaimard, 1833 ).

Siphonaria (Siphonaria) alba — Hubendick 1946: 56, pl. 4, figs 30–31.

Siphonaria sirius — Springsteen & Leobrera 1986: 285, pl. 81, fig. 20; Dharma 1992: 78, pl. 17, fig. 2 (not S. sirius Pilsbry, 1894 ).

Siphonaria atra — Berry 1977: 186, 190, fig. 3; Morton & Morton 1983: 298; Tan & Chou 2000: 117, fig. 117; Tan & Woo 2010: Tan & Low 2014: 367 (not S. atra Quoy & Gaimard, 1833 ).

Siphonaria (Anthosiphonaria) laciniosa — Dharma 2005: pl.79, figs 20a, b (not S. laciniosa ( Linnaeus, 1758)) .

Siphonaria ‘ atra group, unit 39’ Dayrat et al. 2014: 264, fig. 5S.

Material examined. Type material. Lectotype of Siphonaria alba Hubendick, 1943 ; 2. fig. 3, 7, present designation, from Nordwatcher , Javasee [near Singapore, Java Sea ]; coll. C. Aurivillius, 1891. ( UUZM 1574-3957 , colour image unavailable) . Paralectotype, same data as lectotype ( UUZM 1574-3957 ) .

Other, non-type material. Singapore: Lazarus Island causeway, St Johns Island , 01°13.288’N, 103°51.195’E SI04-3 ( AM C.585229 p [M332], C.585230 p [M334], C.585231 p [M335], C.585232 p [M337], C.585237 p [SK175]); Lazarus Island , 01°13.355’N, 103°51.148’E SI04-2 ( AM C.585352 p); Fort Road, drain seawall 01°17.605’N, 103°53.809’E SI01-3 ( AM C.585602 5p); East Coast Park, seawall, 01°18.643’N, 103°57.077’E SI01-2 ( ZRC Moll. 9121 7p, ZRC.MOL.24914 p [M474, SK281], ZRC.MOL.24915 p [SK294]) . PNG: Rempi Area , S Dumduman Is., 05°00,2’S, 145°47,6’E PM12 ( MNHN IM-2013-12000 p [M557]) . Timor-Leste: N of Dili, Christi Rea Beach , 8°32.072’S, 125°36.868’E TL01-2 ( AM C.585905 4p, C.585274 p [M440] . Australia, WA: Kimberley , between the Maret Islands, 14°24’S, 124°58’E ( WAM S72337 p); Caffarelli Is., 16°01.991’S, 123°18.625’E, WA19-1 ( AM C.584678 p [M323]); Conilurus Is, Kimberley, 16°08.875’S, 123°35.234’E, WA18-1 ( AM C.585653 3p, WAM S74082 2p); Catamaran Bay, Cape Levique, Kimberley, 16°27.622’S, 123°00.242’E, WA22-1 ( AM C.585655 4p, C.585296 p [SK424], C.585299 p [M070]); Gantheaume Point, Broome, 17°58.384’S, 122°10.677’E, WA26-2 ( AM C.584735 15p, WAM S74083 5p), CI: Ethel Beach, 10°27.827’S, 105°42.497’E CI02-1 ( AM C.584845 p [M304]) .

Taxonomic remarks. The largest syntype ( UUZM UUMS 3957 /1574) is herein designated as the lectotype of S. alba 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. 49D, E–F ) and geographic series of additional specimens (Table S1). We attribute the record of ‘ S. ferruginea ’ from Christmas Is in Smith (1909: 369) to S. alba based on the similar shell and because S. alba occurs on CI while there is no confirmed record of S. ferruginea (= S. plana ).Throughout the taxonomic literature, Siphonaria alba has frequently been misidentified as S. atra . Records in Berry (1977), Morton & Morton (1983) from Hong Kong, Tan & Chou (2000) from Singapore, Tan & Kastoro (2004) from South China Sea, Tan & Woo (2010) from Singapore, and Tan & Low (2014) from CKI are attributed here to S. alba because these records are within the range of S. alba but outside of the range of other species in the atra group that exhibit similar shells, such as S. bifurcata ( Philippines), S. sirius , S. atra and S. subatra ( Japan).

Morrison (1972: 56–58) treated S. alba as a synonym of S. laciniosa based on similarity in shell form and ‘common reproductive development’. This synonymy is not supported by examination of type specimens and comparative morpho-anatomy.

External morphology ( Fig. 49V ). Foot sole, foot wall, foot edge, mantle, pneumostomal lobe and cephalic folds evenly cream; faint irregular black blotches of pigmentation over centre of cephalic lobes and parts of foot wall; mantle narrow with edge thickened, heavily lobed and white band; genital pore indistinct, located on foot wall to right anterior of right cephalic fold; small black epithelial eye spots centralised on each centrally touching cephalic folds; pneumostomal lobe under the mantle, between the right ADMs.

Shell ( Figs 49D–G ; Table S9): medium sized (max sl mean = 21.9 mm, SD = 3.1 mm, n = 9); height low; circular ovate; apex offset central (commonly eroded); apical sides convex, protoconch direction homostrophic (n = 1,), shell whorl dextral; growth striae indistinct, shell margin thick; rib count (mean = 40.8, SD = 4.6, n = 9), primary ribs narrow to broad, solidly raised, pale white protrude beyond shell lip to unevenly scallop and corrugate the edge, some primary ribs protrude 1–2 mm beyond shell lip, protrusion at shell lip greater at siphonal ridge and the forming primary ribs larger, interspersed with 1–3 pale white finer secondary ribs size; radial colour banding occurs, protoconch area brown, central band paler and shell edge dark brown; rib interstices darker. Interior; spatula, shell margin, ADM scar and siphonal groove evenly white ( Fig. 49D ) or dark chocolate brown ( Fig. 49F ), white rays from shell lip to margin, align under ribs and match rib width; siphonal groove distinct, same colour as shell edge, slightly curved to right anterior; CMS convex thin; thickening and whitening of shell lip occurs (e.g. Fig. 49D ).

Reproductive system ( Fig. 50E; n = 2). Positioned within coelom under the respiratory cavity, hermaphroditic glands positioned to posterior against right foot wall and over foot sole; GP small, singular, positioned through foot wall behind right cephalic fold, GA small, prominent; AO medium sized, elongated, bluntly pointed, slightly bent centrally, joins to top of GA; ED long, narrow, slightly twisted, thickened, joins to back side of GA alongside AO; EG very small, white, folded; single short broad flagellum (F1), appears as extension of ED; AO, GA and ED all muscular white tissue; BD and CD connect closely but in opposing directions into GA between ED and AO joins, both ducts long narrow smooth featureless, pass together through RAM connecting into MG ( BD above CD), BD with distal loop and short MA attached to inner foot wall, additional loop immediately in front of BC; BC large spherical, embedded in folds of MG, test translucent; SV embedded on left side of AG; HD short, thick coils, links small AG to similar sized yellowish granulated HG; MG and AG folded, soft white tissue; sides match curvature of inner foot wall on right posterior of coelom.

Spermatophore ( Fig. 50F ). Relatively long thread-like (length = 13.87 ± 3.24 mm, n = 2, possibly longer as flagellum on one appears incomplete); test thin, translucent, containing a white gelatinous core mass; over half-length comprises a translucent bulbous cylindrical head section (head length = 8.86 mm, SD = 0.65 mm, n = 2; mean ~ 65% of SPM length); tip bluntly rounded; head section much thicker than flagellum (head width = 116 ± 16 μm, flagellum width = 12 ± 0 μm, n = 2); both sections smooth, featureless; 7–8 SPM tightly coiled in one BC ( AM C.585237).

Radula. Dentition formula 44:1:44 ( Hubendick 1946: 56).

Comparative remarks. Siphonaria alba ( atra group, unit 39) is the sister species of a subclade formed by S. atra and S. hienghenensis sp. nov. ( Figs 1 , 2 ). It differs from these two species by COI distances of ≥ 13% ( S. atra ) and ≥ 8.3% ( S. hienghenensis sp. nov.) (Table S3). Throughout its range, S. alba has been found in sympatry with fifteen congeners. Four congeners are sympatric in Singapore: Siphonaria costellata sp. nov. has a taller shell with slightly more raised and even ribbing, a shorter ED and BD, smaller AO and BC, and a shorter SPM. Siphonaria caubianensis sp. nov. has a darker shell exterior and interior, broader and more raised primary ribs, a more posterior and left offset apex, a stronger scalloped shell edge, a smaller AO and BC, no BD distal loop. For comparisons with S. normalis and S. sirius refer to comparative remarks under these species. Two species are sympatric in Cebu, Philippines: For comparisons with S. bifurcata and S. sipho refer to comparative remarks under these species. Siphonaria umbra sp. nov. is sympatric in CI. It has a smaller, darker shell with more even ribbing, smaller AO, shorter, wider ED, and larger BC. Six species are sympatric in Timor-Leste: For comparisons with S. atra , S. viridis , and S. javanica refer to comparative remarks under these species. Siphonaria campestra sp. nov. has a smaller, darker shell with less prominent siphonal ridge and weaker edge scalloping, a smaller AO and BC, shorter ED and BD, and a shorter SPM. Siphonaria forticosta sp. nov. has a larger shell with a slightly more posteriorly offset apex, weaker edge scalloping and darker interior, a smaller AO, shorter ED, and a larger F1. Siphonaria planucosta sp. nov. has a smaller, darker shell with less raised ribbing and weaker edge scalloping, a smaller AO, shorter ED, and shorter SPM. Three species are sympatric in WA (along with S. atra , and S. viridis ): Siphonaria gemina sp. nov. has smaller, taller, paler shell with stronger edge scalloping, a smaller AO, shorter ED and BD, and a less thread-like SPM. Siphonaria restis sp. nov. has a paler shell with more uneven ribbing and stronger edge scalloping, a smaller AO, shorter wider ED, and larger BC. For comparison with S. zelandica refer to comparative remarks under that species.

The RS ( Fig. 50E ) and SPM ( Fig. 50F ) of S. alba shown herein correspond well the RS and SPM figured in Hubendick (1943: 3, fig. 10–11; 1945: 3 figs 10–11) although no serration on SPM flagellum was observed. A specimen from Mindanao figured as ‘ S. acervus ’ in Hubendick (1946:pl. 3, figs 10–12) is probably a specimen of S. alba for exhibiting typical shell characteristics. It is within the known distribution of S. alba . A specimen from Palawan figured as ‘ Siphonaria sirius ’ in Springsteen & Leobrera (1986: 285, pl. 81, fig. 20) is a misidentification and likely a specimen of S. alba for the siphonal ridge exhibiting multiple and not just a single rib. A specimen from Seribu Islands, Java Sea figured as ‘ S. laciniosa’ in Dharma (2005: pl.79, figs 20a, b) is a misidentification and likely a specimen of S. alba as it matches the shell morphology of this species ( Fig. 49D–G ; paired siphonal ribs) and is from within the known range of this species. A specimen from Long Dong, Taiwan figured as ‘ atra group, unit 39’ in Dayrat et al. (2014: 263, fig. 5S) is morphologically consistent with S. alba .

Distribution and habitat. Widely distributed through tropical northwestern Pacific, including Taiwan, Sulawesi, Singapore, Thailand, Philippines, CI, northern Australia (Kimberey, WA) and Timor-Leste, Dili ( Fig. 45 ). In this study found at sheltered positions on moderately exposed rocky shores, at upper and lower littoral levels ( Fig. 49U ).

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 45. Known occurrence records of S. thersites, S. acmaeoides, S. sirius, S. subatra and S. rucuana

FIGURE 49. Shells of S. monticulus, S. alba and S. asghar. A–C, O–P, T. S. monticulus. A. Lectotype of Hebesiphon monticulus AM C.103720. B–C. NC, Lifou, TS. B. AM C.584951 [M387]. C. AM C.584950 [M386]. O. Protoconch, AM C.584945 [SK056]. P, T. Lifou, in situ and animal. D–G, U–V. S. alba. D. Singapore, ZRC.MOL.24915 [SK294]. E. Singapore, AM C.585230 [M334] F. WA, AM C.585299 [M070]. G. Singapore, AM C.585237 [SK175]. U–V. Singapore, in situ and animal. H–N, Q–S. S. asghar. H. Holotype NHMUK 1958.6.13.13. I–K. Paratypes NHMUK 1958.6.13.14. L–R. Pakistan, Karachi, TS. L. AM C.585845 [M245]. M. AM C.585844 [M244]. N. AM C.585846 [M256, SK190]. Q. AM C.586001 [SK532]. R. AM C.585855 [M236]. S. In situ. Unlabelled scale bars = 10 mm.

FIGURE 50. Reproductive morphology of S. monticulus, S. alba, S. asghar and S. propria. A–D. S. monticulus, TS, Lifou. A–B. AM C.584951 [M387]. C–D. AM C.584944 [SK057]. E–F. S. alba, Singapore, Lazarus Is, AM C.585237 [SK175]. G–H. S. asghar. G. Pakistan, Karachi, AM C.585846 [M458, SK190]. H. Karachi, AM C.586001 [SK532]. I–K. S. propria NZ, N Island, NMNZ M.331452 [M509]. Scale bars = 1 mm.