Siphonaria fuliginata 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 : 94-96

Siphonaria fuliginata Reeve, 1856

( Figs 35G–I, Q , 36D–E )

Siphonaria fuliginata Reeve 1856 : pl. 7, species 34 (without type locality).— Paetel 1883: 178; 1889: 428; Hanley 1858b: 152; Hubendick 1946: 67; Galindo 1977: 416; Trew 1983: 7; White & Dayrat 2012: 63 (as ‘ nomen dubium ’).

Materialexamined. Typematerial. Holotypeof Siphonaria fuliginata Reeve, 1856 ( NHMUK MC.1981002 , Fig. 35G ).

Other, non-type material. Rodrigues: Rivière Banane, N coast, 19°11.25’S, 63°22.866’E RG01-1 ( AM C.585896 6p, C.585190 p [M428, SK331], C.585191 p [M429, SK332], C.585194 p [SK369]; Anse Quiter, SW coast, 19°46.183’S, 63°22.866’E, RG02-1 ( AM C.585874 p [M430, SK134]).

Taxonomic remarks. No type locality has been given in the original description of Reeve (1856). For its unknown origins, this taxon has subsequently been considered as a nomen dubium by White & Dayrat (2012). However, examining freshly collected from Rodrigues revealed a shell form that closely resembled the features of the holotype. We therefore infer that these samples and the type of S. fuliginata are conspecific. Here, we provide a detailed redescription of S. fuliginata based on samples from Rodrigues to remove the uncertainty about the identity of this species.

External morphology. Foot wall, mantle, cephalic folds and pneumostomal lobe all evenly pale cream in colour;dark pigmentation markings absent,foot sole darker cream, foot edge paler; Mantle translucent, narrower than foot wall, lobed with a thickened edge, pneumostome wide between right ADMs and within mantle.

Shell ( Figs 35G–I ; Table S9). Small sized (max sl mean = 9.7 mm, SD = 2.9 mm, n = 3), ovate, height medium to low, apex weakly offset central and left, apical sides convex, protoconch direction undetermined, shell whorl dextral growth lines distinct; rib count (mean = 27, SD = 1.7, n = 3), raised, whitish, straight, rib width increases to shell lip; rib interstices paler, may have irregular red/brown markings; ~ 9 primary ribs, extend from apex to shell edge, similar secondary ribs between primary ribs; paired primary ribs over siphonal ridge; shell lip weakly scalloped, corrugated aligning with rib ends; interior colouration of margin rays match underside of white primary ribs and brown rib interstices, inner margin often brown from inner margin to the golden (often mottled blue) coloured spatula ( Fig. 35H ); ADM impression and siphonal groove distinct, paler than shell margin colouring, cephalic scar convex; thickening and whitening of shell lip/margin not observed; some shells may be display dark brown exterior and interior (AM C.585191).

Reproductive system ( Fig. 36D; n = 3). Positioned within coelom under the respiratory cavity, epiphallic parts positioned between RAM and over back of BM close. ED joins at underside of small GA, AO short, bluntly pointed, smaller than GA, joins through underside of ED; ED thick, elongated, centrally twisted, broader at EG; single broad curled stubby flagellum F1, appears as extension of ED at connection with EG; AO, GA and ED all muscular white tissue; EG broad, relatedly large, soft white folded tissue; BD and CD connect in parallel to GA at top and side of GA respectively; BD without distal loop or MA, slightly longer and thinner than CD, both ducts smooth and pass together between RAM and inner foot wall connecting into thick layered folds of MG (BD over CD), bursal loop in BD immediately in front of BC; BC relatively large, spherical, embedded along with part of BD in AG/MG; SV embedded in AG under BC; HD short, narrow, straight, links large AG to a much smaller yellowish granulated HG, AG and MG folded, inner edge MG lobed, both soft white tissue, with outer sides curved reflecting the close positioning to curvature of inner foot wall at right posterior quarter of coelom, MG flattened against inner foot sole.

Spermatophore ( Fig. 36E ). Bulbous, test thin, translucent (length = 1.43 mm, n = 1, AL = 6.5 mm); head cylindrical, broad, tip bluntly rounded, containing a white gelatinous core, tapers into short flagellum; both sections smooth, featureless; head longer and thicker than flagellum (head length = 1.03 mm, ~ 89% of total length, head width = 138 μm, flagellum width = 35 μm, n = 1); 2 SPM tightly coiled in cream gelatinous mass in one BC ( Fig. 36E ).

Comparative remarks. Siphonaria fuliginata ( normalis group, unit 80) is closely related to S. normalis (unit 14) and S. madangensis (unit 88) ( Figs 1 , 4 ). It differs from these two species by COI distances of ≥ 5.9% ( S. normalis ) and ≥ 4.4% ( S. madangensis ), respectively (Table S8). From the next more closely related species, S. costellata , it differs by COI distances of ≥ 6.5%. The close phylogenetic relationships with S. normalis , S. madangensis , and S. costellata are reflected in shared similarities in shell characters (thickened white shell lip variations) and the RS (broad epiphallic parts). However, S. normalis has a darker, more finely ribbed shell, a longer, narrower BD, larger BC, and a longer SPM. Siphonaria madangensis sp. nov. has a darker shell with a more central apex and prominent siphonal ridge, a smaller to indistinct AO, BD without a bursal loop, and a more bulbous SPM. Siphonaria costellata sp. nov. has a larger, taller, more brownish (less grey) shell, with a more central apex, a smaller AO, and wider BD without a bursal loop. Siphonaria fuliginata has been found in sympatry with Siphonaria rodriguensis sp. nov. on Rodrigues Is, which has a smaller, taller, darker shell with pale parallel-marked primary ribs, a longer wider BD, larger BC and AG, and longer, narrower SPM.

Distribution and habitat. Known only from Rodrigues, Indian Ocean ( Fig. 37 ). In the present study found in sheltered positions on moderately exposed rocky shores, mid littoral level, amongst barnacles ( Fig. 35Q ).

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 35. Shells of S. bifurcata, S. fuliginata and S. lirata. A–F, O–P, S. S. bifurcata. A. Lectotype NHMUK 1979169/1. B–D. Paralectotypes NHMUK 1979169/2-4. E. Philippines, Cebu, TS, AM C.585118 [M414, SK097]. F. Philippines, Polillo Is, TS, WAM S74096 [SK073]. O. Animal & P. Cebu, in situ. S. Protoconch, WAM S74098 [SK410]. G–I, Q. S. fuliginata. G. Holotype NHMUK 1981002. H. Rodrigues, AM C.585194 [SK369]. I. Rodrigues, AM C.585874 [M430, SK134]. Q. Rodrigues, in situ. J–N, R, T–V. S. lirata. J. Lectotype NHMUK 1979028/1. K–M. Paralectotypes NHMUK 1979028/2-4. N, R. Guam, Apra. N. AM C.585832 [M448, SK242]. R. AM C.585192 [SK252]. T–U. Guam, in situ. V. Protoconch,AM C.585833 [M449]. Unlabelled scale bars = 10 mm.

FIGURE 36. Reproductive morphology of S. bifurcata, S. fuliginata and S. lirata. A–C. S. bifurcata. A. Philippines, Polillo Is, TS, WAM S74096 [SK073]. B. Polillo Is, TS, WAM S74097 [SK412]. C. Cebu, TS, AM C.585118 [M414, SK097]. D–E. S. fuliginata, Rodrigues. D. AM C.585874 [M430, SK134]. E. AM C.585194 [SK369]. F–H. S. lirata, Guam, Apra. F. AM C.585832 [M448, SK242]. G–H. AM C.585833 [M449, SK162]. Scale bars = 1 mm.

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