Siphonaria belcheri Hanley, 1858

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 : 103-104

Siphonaria belcheri Hanley, 1858

( Figs 39C–D , 40A–J, R )

Siphonaria belcheri Hanley 1858b: 153 (‘probably taken in the Indian seas’ [Indian Ocean]).— Paetel 1883: 178; 1889: 428; Hubendick 1947a: 163; Bosch et al. 1995: 185, fig. 859; Ali et al. 2011: 1086, fig. 1B; Coan & Kabat 2012: 336; White & Dayrat 2012; 61; Vakani et al. 2021: 134, fig. 2a.

Siphonaria (Patellopsis) belcheri — Hubendick 1945: 70; 1946, 34, pl. 2, fig. 5–8; Knox 1955: 88.

Siphonaria kurracheensis — Moazzo 1939: 7, 280, fig. 2; Dayrat et al. 2014: 268, ‘unit 27’, fig. 5 D (not S. kurracheensis Reeve, 1856 ).

Material examined. Type material. Lectotype of Siphonaria belcheri Hanley, 1858 , present designation ( NHMUK 1900.3.19.29 , Fig. 40A ). Six paralectotypes, same data as lectotype ( NHMUK 1900.3.19.28 , 30–34 , Figs 40B–G ).

Other, non-type material. Pakistan: Karachi, Clifton Beach 24°45.500’N, 67°05.968’E, PA02-1 ( AM C.585449 10p, C.585102 p [M227], C.585103 p [M228], C.585106 p [SK147], C.585500 p [SK146], C.595930 p [SK533]); French Beach , 24°50.367’N, 66°49.387’E, PA01-1 ( AM C.585382 10p, C.585100 p [M237], C.585101 p [M238]), 24°50.345’N, 66°49.244’E, PA01-2 ( AM C.585669 6p) .

Taxonomic remarks. The largest syntype is herein designated as the lectotype of S. belcheri ( Fig. 40A ) 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 (‘Indian Ocean’, from Pakistan; Figs 40H, J ) and geographic series of additional specimens (Table S 1).

External morphology. Foot wall, mantle and pneumostomal lobe evenly grey, foot sole darker grey; edge of foot sole/wall, cephalic folds and foot wall mantle join fade to pale cream; mantle translucent, wider than foot wall, elongated at anterior, edge thickened lobed whitish with black bands aligning to rib interstices; pneumostome within mantle, between right and posterior ADMs.

Shell ( Figs 40A–J ; Table S9). Small sized (max sl mean = 12.08 mm, SD = 1.38 mm, n = 3), circular ovate; height medium; exterior maybe uneven, apex offset weakly to posterior and left, apical sides weakly concave, protoconch direction heterostrophic (n = 1), curls below apex to posterior, shell whorl dextral; growth striae prominent, shell thickness thick; rib count (mean = 33, SD = 3.3, n = 3), primary ribs pale white, fairly straight, ridge raised, rounded, may broaden significantly to shell lip, rib interstices; shell lip to scalloped and weakly corrugated; finer irregular secondary ribs fill gap between primary ribs, rib interstices brown; paired primary ribs form siphonal ridge. Interior shell margin golden brown with irregular mottled dark brown, shell lip white with brown rays under rib interstices variably extending over margin or to spatula, centre of spatula dark brown often orange; siphonal groove distinct, same colour as shell edge; ADM scar indistinct, CMS straight; thickening of shell lip occurs in more mature specimens, in-fills and reduces lip scalloping.

Reproductive system ( Fig. 39C; n = 2). Positioned within right side of coelom, against foot wall on foot muscle, under the respiratory cavity; epiphallic parts positioned between BM and RAM. GA small, with singular GP through foot wall; AO large broad bluntly pointed, joined to upper GA; ED elongated narrow thickened, slightly centrally bent, joins to lower side of GA; GA, AO, ED all white muscular fibrous tissue; EG large, soft whitish tissue, folded, joins ED; single wide flagellum (F1), shorter but similar width to ED, appears as an extension of ED. BD and CD connect in opposing directions into GA between ED join and GP, both ducts narrow long straight smooth whitish, pass together through RAM ( BD over thicker CD) into soft white folded tissues of MG, BC embedded in folds close to embedded blackish SV; BD long narrow with prominent distal loop and MA to inner anterior foot wall; CD long, wider than BD; BC relatively small bulbous, thin whitish translucent test (yellowish gelatinous mass in BC); MG / AG complex relatively large; HD short narrow coiled, links ducts in soft white folded tissues of AG to yellowish granulated HG; AG / MG larger than HG, sides match curvature of inner foot wall.

Spermatophore ( Fig. 39D ). Broad head with short flagellum, coiled (length = 0.57 ± 0.09 mm, n = 2); head section cylindrical, bulbous, elongate, rounded tip; test smooth, featureless, translucent encasing a white opaque central core; tapering section merges head to flagellum; head longer, wider than translucent flagellum (head length = 0.51 ± 0.07 mm, ~ 90% of SPM length, head width = 47 ± 9 μm; flagellum width = 6 ± 0 μm, n = 2); 2 SPM coiled in one BC ( AM C.595930).

Radula. Dentition formula 12:1:12 ( Hubendick 1946: 38).

Comparative remarks. Siphonaria belcheri ( atra group, unit 27) is the sister species of S. madagascariensis in our mitochondrial tree ( Figs 1 , 2 ). It differs from other species by COI distances of ≥ 20% (Table S%).

We found S. belcheri in sympatry with four congeners in Oman and Karachi, Pakistan. Siphonaria asghar has a lower shell with uneven ribbing, weaker edge scalloping, a larger BC, and a smaller, indistinct AO. Siphonaria perexigua sp. nov. has a lower shell with broader, more raised ribs, weaker edge scalloping, a shorter, bulbous, blunt AO, longer, wider ED and BD, and a larger BC. For comparisons with S. kurracheensis and S. crenata refer to comparative remarks under these species.

The RS structure of S. atra and S. bifurcata resemble that of S. belcheri ; however, these species differ in shell morphology and are genetically highly distinct. Figures of ‘ S. belcheri ’ in Hubendick (1946: 90, pl. 2, figs 5–8, from ‘Persian Gulf’), are specimens of S. belcheri . However, the RS figured and described in Hubendick (1946: 10, fig. 7) differs from that shown herein in details of epiphallic parts, omitting AO, F1, distal loop in BD and opposing connections of BD and CD. Hubendick’s RS figure and description matches that of S. carbo , which Hubendick (1946: 35) indicated was ‘of the same type’. Figured specimen of ‘ S. kurracheensis ’ in Moazzo (1939: 7, 280 fig. 2 closely resembles S. belcheri (in particular the weakly ribbed paralectotype; Fig. 39G ). Figured specimen of ‘unit 27, S. kurracheensis’ from Masirah Is, Oman in Dayrat et al. (2014: 263, fig. 5D) matches the coarser ribbed form of S. belcheri rather than the narrower/finer ribbed S. kurracheensis .

Distribution and habitat. Coasts of the Arabian Sea, recorded from Masirah Island, Oman, Karachi, Pakistan, and India ( Fig. 37 ). In the present study found in sheltered positions on exposed rocky shores, upper to mid littoral level ( Fig. 40R ).

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 37. Known occurrence records of S. bifurcata, S. fuliginata, S. lirata, S. exulum, S. belcheri, S. nuttallii, S. incerta and S. tasmanica

FIGURE 39. Reproductive morphology of S. carbo, S. belcheri, S. exulum and S. nuttallii. A–B. S. carbo, Mozambique, MNHN IM 2019-16165 [M587]. C–D. S. belcheri, Pakistan, Karachi. C. AM C.585500 [SK146]. D. AM C.595930 [SK533]. E–H. S. exulum. E. NI, TS, AM C.585025 [SK041]. F. LHI, AM C.546717 [SK052]. G–H. Kermadec Is, Raoul Is, TS of S. raoulensis. G. AM C.475847 [M513]. H. AM C.475848 [M512]. I–J. S. nuttallii, Hawaii, Maui, TS. I. AM C.584898 [SK211]. J. AM C.584895 [M471, SK273]. Unlabelled scale bars = 1 mm.

FIGURE 40. Shells of S. belcheri, S. nuttallii and S. thersites. A–J, R. S. belcheri. A. Lectotype NHMUK 1900.3.19.29. B–G. Paralectotypes NHMUK 1900.3.19.30-34. G. NHMUK 1900.3.19.28. H. Pakistan, Karachi, AM C.585102 [M227]. I. Karachi, AM C.585500 [SK146]. J. Karachi, AM C.585101 [M238]. R. Karachi, in situ. K–N, S, U–V. S. nuttallii. K. Lectotype NHMUK 20120166/1. L. Hawaii, Maui, TS, AM C.584898 [SK211]. M. TS of S. chirura AM C.584895 [M471, SK273]. N. Paralectotypes NHMUK 20120166. S. Protoconch, AM C.584894 [M470]. U. Maui, in situ. O–Q, T. S. thersites, O. Holotype USNM 11852. P–Q. Alaska, Cook Inlet. P. CBG 11BIOAK-0592 [SK553]. Q. 11BIOAK-0589 [SK554]. T. Washington, Neeah Bay, TS, in situ. Unlabelled scale bars = 10 mm.