Siphonaria radiata ( Blainville, 1826 )

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 : 38-40

Siphonaria radiata ( Blainville, 1826)

( Figs 17A–B, U–V , 18A–B )

Pileopsis radiata Blainville 1826: 462 (type locality unknown).

Siphonaria radiata — Blainville 1827a: pl. 2, figs 4, 4a (as ‘radiée’); 1827b: 294 (type locality unknown); Lamarck 1836: 556, 1839: 205; Jay 1839: 39; Catlow & Reeve 1845: 100; Hanley 1858b: 152; H. Adams & A. Adams 1855 (in 1853–58): 271; 1863: 271; Paetel 1889: 429; Morrison 1972: 52; Galindo 1977: 416; Jenkins 1982: 12, White & Dayrat 2012: 67.

Siphonaria ‘ normalis group, unit 12’, Dayrat et al. 2014: 260, fig. 3N.

Material examined. Type material. Neotype of Pileopsis radiata , present designation, Malaysia, Port Dickson , 02°31.234’N, 101°48.026’E; coll. B.W. Jenkins, 15 Feb 2015, PD01-1 ( AM C.585861 , Fig. 17A ).

Other, non-type material. Malaysia: Bak Bak Beach, Kudat , Sabah, 07°00′ N, 116°46′ E ( AM C.585236 20p, C.595941 d [SK523]); Bukit Keluang, Terengganu, 5°47.81’N, 102°36.43’E ( ZRC 1999-1978 12p; ZRC. MOL.24900 p [M528, SK444], ZRC.MOL.24901 p [M596, SK528]); Port Dickson, 02°31.234’N, 101°48.026’E PD01-1 ( AM C.585959 3p, C.585821 7d, C.585921 p [SK337 protoconch H2]); Air Papan, Mersing, Johor, 2°30.98′ N 103°50.1’E ( ZRC 1999-1755 20p, ZRC. MOL.24895 p [M527]; ZRC.MOL.24896 p [M526]); Tg. Bidara, Malacca, 02°17.568’N, 102°5.207’E ( ZRC 1999- 1746 9p; ZRC.MOL.24891 p [SK348], Fig. 17B ; ZRC. MOL.24892 p [M525], ZRC.MOL.24893 p [M595], ZRC.MOL.24894 p [M594]); Pulau Langkawi, 6°18′ N, 99°52′ E ( AM C.595974 20+p, C.585098 p [SK525], C.585697 p [SK524]) .

Taxonomic remarks. Blainville (1826: 462) introduced the new name Pileopsis radiata , and subsequently transferred it to Siphonaria in Blainville (1827a: pl. 2, figs 4,4a; 1827b: 294). The original type material is considered lost; no types were found in the MNHN (Philippe Bouchet, pers. comm.). The neotype is designated herein in accordance with Art. 75.3 of the Code to clarify the identity of this nominal taxon as well as to restrict its type locality. Blainville’s name is not invalidated by S. radiata Gray, 1824 , which is not an available name (for details see under S. sipho ). Siphonaria radiata ( Blainville, 1826) is a senior secondary homonym of S. radiata Sowerby I, 1835 (not reviewed herein) and S. radiata A. Adams & Reeve, 1850 , which has been replaced by S. radians H. Adams & A. Adams, 1855 . Hubendick (1946: 49) incorrectly considered S. radiata (Blainville, 1827) a synonym of S. australis .

External morphology. Foot sole grey, paler to foot edge; foot wall bluish to inner, evenly dark cream, with irregular black pigmented blotches, paler to foot, pustules prominent; cephalic folds thick, narrow, irregular black pigmentation darker over centre of cephalic folds; mantle wide thin translucent edge lobed thickened band; eye spots prominent, pneumostome small, under mantle.

Shell ( Figs 17A–B, V ; Table S9). Small sized (max sl mean = 13.29 mm, SD = 1.55 mm, n = 42), circular ovate, height medium to tall; apex slightly curved, apex offset slightly to posterior and left, apical sides convex, posterior strongly concave, protoconch direction weakly heterostrophic to central (n = 1; Fig. 17V ), shell whorl dextral, shell thick; growth striae prominent, even, unraised; radial colour bands indistinct; rib count (mean = 30, SD = 3.1, n = 42), primary ribs distinct from secondary ribs; ~ 16 pale brown to off white primary ribs, ridges raised, rounded; siphonal ridge formed by paired adjacent primary ribs, most primary ribs broaden weakly, project beyond shell lip (especially siphonal ridge) with ends slightly raised to scallop and corrugate shell edge; 0–2 finer secondary ribs between primary ribs, rib interstices darker. Interior shell margin and spatula dark brown to golden tan, often some calcification; off white to cream rays on shell margin align under primary/secondary ribs, extend to spatula; siphonal groove distinct, paler than margin; ADM scar indistinct, similar to margin and spatula; CMS straight; whitening and thickening of shell lip observed.

The neotype ( Fig. 17A ). Shell (sl = 15.1, sw = 10.8, sh = 5.5 mm) circular ovate; thick, apex offset weakly offset to posterior and left, apical sides straight, 32 ribs, ~17 whitish primary ribs, with 0–2 in between secondary ribs, rib interstices dark, siphonal ridge formed by adjacent dual primary ribs. Interior evenly dark brown, white rays on shell lip under ribs.

Reproductive system ( Fig. 18A; n = 4). Positioned within coelom under the respiratory cavity, hermaphroditic glands positioned to posterior against right foot wall and over foot sole, epiphallic parts between RAM and extending over BM; ED distinct entry to top of small GA, AO small, short, bent, tip blunt, bulbous, appears part of GA under ED; ED thick, short, centrally bent; AO, GA and ED all muscular white tissue; EG very large, elongated, 2 lobes, folded, soft white tissue; single thick elongated blunt flagellum F1 appears as extension of ED at EG join; BD and CD connect closely together into GA, both ducts smooth, short, broad, slightly bent, pass together through outer edge of RAM ( BD over CD) connecting into MG; BC medium to large, bulbous, white opaque test, embedded along with part of BD in soft white folds of MG; HD short, broad, coiled, links soft white folded AG to small yellowish granulated HG; AG larger than HG, both with outer sides curved reflecting the close positioning to curvature of inner foot wall at right posterior quarter of coelom; SV embedded in AG close to BC.

Spermatophore ( Fig. 18B ). Broad head with short flagellum (length = 4.6 ± 0.57 mm, n = 2); head section cylindrical, bulbous, centrally bent, tip rounded; test thin, smooth, featureless, translucent encasing a white opaque central core; short looped tapering section merges head to filamentous flagellum; head slightly shorter, wider than translucent flagellum (head length = 2.28 ± 0.67 mm, n = 3; flagellum length = 2.38 mm, n = 1; length/head length ~ 52%; head width = 172 ± 17 μm; flagellum width = 26 ± 0 μm, n = 3); 5 SPMs tightly coiled in cream gelatinous mass in BC of one specimen ( Fig. 18B ).

Comparativeremarks. Siphonariaradiata ( normalis group, unit 12) is the sister species of S. planucosta sp. nov. ( Figs 1 , 4C ). Both species are separated from each other species by distances of at least 11.5% in COI (Table S8). The lowest interspecific genetic distances were observed between S. radiata and S. madangensis sp. nov. (unit 88) = 10.7%, S. costellata sp. nov. (unit 13) = 11%, and S. normalis (unit 14) = 11.4%) (Table S8).

We found a sympatric congener in Sabah: Siphonaria kudatensis (for comparison refer to S. kudatensis ). Siphonaria radians has a lower, slightly larger shell with finer ribbing, a less prominent siphonal ridge, weaker edge scalloping, a larger AO, longer twisted ED, longer narrower BD with distal loop and a smaller BC. Shell geometry and sculpture of S. radiata resemble that of S. costellata sp. nov. (unit 13) and S. normalis (unit 14). However, S. radiata possesses slightly fewer and broader primary ribs, fewer secondary ribs, narrower interstices, more prominent siphonal ridge and more scalloped edge than these two species. The interior colouration also differs being generally paler browns to white with prominent red-brown rays extending to spatula in S. radiata . The SPM of S. radiata resembles that of S. normalis and S. gemina sp. nov. The record of ‘ S. cf kurracheensis’ in Way & Purchon (1981: 321) is a misidentification and likely of S. radiata . The specimen figured as ‘ normalis group, unit 12’ in Dayrat et al. (2014: 260, fig. 3N) corresponds well with the present species.

Distribution and habitat. Recorded from W coast of Thailand and Port Dickson, Malacca Strait, Malaysia ( Fig. 16 ). In this study, found on exposed and bare rocky shores, mid littoral level ( Fig. 17U ).

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 16. Known occurrence records of S. obliquata, S. radiata, S. diemenensis, S. australis, S. atra and S. denticulata

FIGURE 17. Shells of S. radiata, S. diemenensis, S. australis and S. capensis. A–B, U–V. S. radiata. A. Malaysia, Port Dickson, neotype AM C.585861 [M408]. B. Malacca, ZRC.MOL.24891 [SK348]. U. Port Dickson, in situ. V. Protoconch, AM C.585921 [SK337]. C–G, O–Q. S. diemenensis. C. Lectotype MNHN-IM-2000-35952. D. Tas, TS, AM C.584797 [SK047]. E. Tas, AM C.585270 [M107]. F. Vic, AM C.585286 [M168]. G. Tas, AM C.585260 [M170]. O. Animal. P. Tas, TS, in situ. Q. Protoconch, Vic, AM C.585357 [SK029]. H–J, R–T. S. australis. H. Lectotype MNHN-IM-2000-5036. I. NZ, Stewart Is, AM C.585249 [M481, SK288]. J. Stewart Is, AM C.585247 [M480, SK289]. K. Holotype of S. inculta USNM 5857. R–S. In situ and animal. T. Protoconch, AM C.265856 [SK511]. L–N. S. capensis. L. Lectotype MNHN IM 2000-38235. M. South Africa, MNHN-IM-2019- 1481 [M585]. N. IM-2019-1477 [M584]. Unlabelled scale bars = 10 mm.

FIGURE 18. Reproductive morphology of S. radiata, S. crenata and S. capensis. A–B. S. radiata, Malaysia, Malacca, ZRC. MOL.24891 [SK348]. C–E. S. crenata, Pakistan, Karachi, C. AM C.585851 [M242, SK233]. D. AM C.585338 [SK153]. E. AM C.595917 [M592, SK534]. F–G. S. capensis, Mozambique, Inhaca. F. MNHN IM-2019-1488 [SK507]. G. MNHN IM-2019-1481 [M585]. Unlabelled scale bars 1 mm.