Siphonaria radians H. Adams & A. Adams, 1855

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 : 83-84

Siphonaria radians H. Adams & A. Adams, 1855

( Figs 30H–I , 31J–K )

Siphonaria radiata A. Adams & Reeve 1850: 69 , pl. 13, fig. 2a–b (invalid, preoccupied by Blainville, 1826).— Paetel 1889: 429; White & Dayrat 2012: 67.

Siphonaria radians H. Adams & A. Adams 1855 (in 1853–58): 271 (replacement name for S. radiata A. Adams & Reeve, 1850 not Blainville, 1826 nor Sowerby I, 1835).—H. Adams & A. Adams 1863: 271; Paetel 1889: 429; Hylleberg & Kilburn 2003: 133; White & Dayrat 2012: 67.

Siphonaria (Sacculosiphonaria) radians — Hubendick 1946: 43.

Material examined. Type material. Neotype of Siphonaria radians , present designation, from Natuna Regency , Riau Islands, NE coast of Palau Panjang (NW of Pulau Natuna Besar ), Indonesia, South China Sea. 04°15.9’N, 108°12.27’E, Expedition Anambas, ZRC EA-ZJ09 ; coll. 17 March 2002 ( ZRC. MOL.24912 [M519, SK435], Fig. 31J ).

Other, non-type material. Indonesia: Pulau Panjang , Riau Islands 1°10.215’N, 104°18.905’E ZRC EA ZJ09 ( AM C.595976 p [M590, SK512], C.595977 p [M591, SK513]) . Malaysia: Bak Bak Beach, Kudat , Sabah 07°00′ N, 116°46′ E ( AM C.585940 p [SK521]); Tangung Bidara, Malacca 2°17.568’N, 102°5.207’E ( ZRC.MOL.24893 p [M595, SK527], ZRC.MOL.24894 p [M594, SK526], Fig. 31K , Pulau Langkawi 6°18′ N, 99°52′ E ( AM C.585697 p [SK524]).

Taxonomic remarks. The name S. radiata A. Adams & Reeve, 1850 is a junior secondary homonym of S. radiata ( Blainville, 1826) and a junior objective homonym of S. radiata Sowerby I, 1835 . It is not invalidated by S. radiata Gray (1824) , however, which is an unnecessary replacement name (see under S. sipho ). H. Adams & A. Adams (1855) introduced S. radians as a replacement name (Art. 12.2 of the Code). No type material of S. radiata A. Adams & Reeve, 1850 could be found in the NHMUK and the types are therefore considered lost. The neotype of Siphonaria radians is designated herein to clarify the taxonomic status and the type locality of this taxon (Art. 75.3 of the Code).

External morphology (preserved). Foot sole grey, lighter to foot edge; mantle, footwall, pneumostome and cephalic lobes cream with irregular darker pigmentation markings concentrated over cephalic lobes, mantle thin translucent lobed with white edge band and black marking aligning under rib interstices.

Shell ( Figs 31J, K ; Table S9). External sculpture and height variable, lower fine ribbed form ( Fig. 31J ), taller prominent ribbed form ( Fig. 31K ); small to medium sized (max sl mean = 16.8 mm, SD = 2.1 mm, n = 11), circular ovate, low; apex slightly curved, apex offset slightly to posterior and left, apical sides weakly convex, posterior straight to concave, protoconch direction weakly homostrophic to central (n = 1), shell whorl dextral, shell thin, growth striae prominent, even, unraised; radial colour bands indistinct; rib count (mean = 48, SD = 12.4, n = 11), primary ribs indistinct from secondary ribs; ~ 16 pale brown to off white indistinct primary ribs, ridges weakly raised, rounded; siphonal ridge formed by 3 primary ribs, align with shell lip; shell edge uneven, weakly scalloped and corrugated; 2–3 finer secondary ribs between primary ribs, rib interstices darker. Interior shell margin and spatula dark chocolate brown, centre of spatula and distinct siphonal groove paler, off white to cream rays on shell margin, align under primary/secondary ribs; ADM scar distinct, similar to margin and spatula; CMS convex; whitening or thickening of shell lip not observed.

The neotype ( Fig. 31J ). Shell (sl = 17.9, sw = 14.2, sh = 5.2 mm) circular ovate, low; apex offset weakly to posterior and left, exterior grey, 68 fine weakly curved ribs; siphonal ridge formed by three adjacent ribs. Interior shell lip chocolate brown and cream under rib ends, dark brown rays on shell lip aligning under rib interstices. RS ( Fig. 30H ).

Reproductive system ( Fig. 30H; n = 5). Positioned within right side of coelom, against foot wall on foot muscle, under the respiratory cavity, epiphallic parts positioned between inner side RAM and behind BM; GA medium, with singular GP through foot wall; AO medium sized, broad, bluntly pointed, central bend, joined to upper GA; ED short wide, centrally twisted, joins to outer side of GA; GA, AO, ED all white muscular fibrous tissue; EG large sized, soft whitish tissue, folded, joins at junction of end of ED and extension of single broad long twisted flagellum (F1); BD and CD connect closely in opposite directions into GA between ED junction and GP, CD junction into GA bulbous, both ducts long, smooth, narrow, whitish, featureless, pass closely together outside RAM ( BD over CD) and broaden at junction into soft white folded tissues of MG; BD with distal loop and MA; CD connects to large MG / AG complex; BC embedded in MG folds, close to embedded SV; BC small, thin whitish translucent test; HD short, wide, coiled, links ducts in soft white folds of AG to yellowish granulated HG; outer edge of MG lobbed; AG slightly larger than HG.

Spermatophore ( Fig. 30I ). Thread-like, test thin, comprises a translucent cylindrical body section containing a white gelatinous core, tapers rapidly into a filamentous transparent flagellum (head length = 8.34 ± 1.5 mm, n = 4, ~ 76% of SPM length, head width = 168 μm, ± 33 μm; flagellum width = 19 μm ± 2 μm), head section much thicker than flagellum, head tip bluntly rounded; both sections smooth, featureless; 3 and 4 SPM coiled, embedded in whitish gelatinous mass within 2 BC’s.

Comparative remarks. Specimens identified as S. radians herein match well the original description and figures of S. radiata (A. Adams & Reeve, 1850) . Siphonaria radians ( atra group, unit 95) is the sister species of S. umbra sp. nov. (unit 46). Both species together form a well-differentiated and well-supported subclade ( Figs 1 , 2 ). Both species differ from each other by COI genetic of ≥ 21.8% (Table S4). Throughout its range, S. radians has been found in sympatry with three congeners. On the Riau Islands it occurs in sympatry with Siphonaria sipho ; for comparative remarks refer to that species. Two congeners are sympatric at Kudat, Sabah, E. Malaysia. For comparisons with these species refer to comparative remarks under Siphonaria radiata and S. kudatensis sp. nov., respectively.

Specimens from Malaysia and China Sea match the shell sculpture (wide to fine and wavy ribbing), external (grey/brown) and internal colouration (black and white rays on shell margin, typical for this species. A specimen figured as ‘ Siphonaria radians ’ in Habe & Kosuge (1966: pl. 42, figs 24, 25) is attributed to S. rucuana .

Distribution and habitat. Currently known only from Riau Islands, Indonesia and Sabah, E Malaysia ( Fig. 25 ). Found on rocky headlands, at upper and lower 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 30. Reproductive morphology of S. plana, S. plicata, S. lateralis and S. radians. A–B. S. plana, Mauritius, AM C.584970 [M252]. C–D. TS of S. plicata, Tonga, Tongatapu. C. AM C.585276 [SK106, M419]. D. AM C.585275 [SK104, M418]. E–G. S. lateralis, Macquarie Island, TS of Kerguelenella innominata. E–F. AM C.91959 [SK202]. G. AM C.584960 [M468, SK270]. H–I. Indonesia, Riau Islands, Neotype of S. radians ZRC.MOL.24912 [M519, SK435]. Scale bars = 1 mm.

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.