Siphonaria bourailensis, B. W. Jenkins & Köhler, 2024

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 : 174-175

Siphonaria bourailensis sp. nov.

( Figs 68F–J, O–P, 69E–F)

Material examined. Type material. Holotype, from Bonhomme de Bourail , La Roche Percee, 21°36.487’S, 165°27.423’E, NC; coll. B.W. Jenkins, NC06-3, 28 Oct 2018 ( AM C.585017 [M368], Fig. 68F) . Paratypes: same data as holotype ( AM C.608182 p [SK126], Fig. 68J, C.585466 p [M372] Fig. 68H); We Baie de Chateaubriand, East coast Lifou , Loyalty Islands, NC, 20°54.779’S, 167°15.636’E; coll. B.W. Jenkins, LFU01-1, 22 Oct 2018 ( AM C.585438 p [M390], Fig. 68I) .

Other, non-type material. NC: Poum 2, 20°13.754’S, 164°01.699’E, NC05-3 ( AM C.586000 4p); Ponerihouen, 21°05.644’S, 165°26.646’E, NC03-1 ( AM C.584807 p [M360]); Bonhomme de Bourail , La Roche Percee, 21°36.487’S, 165°27.423’E, NC06-3 ( AM C.585331 p [SK125 protoconch I2]); Presq’ile Ducos Baie des Dames, Noumea, 22°14.170’S, 166°24.524’E, NC01-1 ( AM C.584804 4p) .

External morphology ( Fig. 68O). Foot sole and foot wall evenly cream, without black pigmentation, paler to foot edge and mantle edge; even blackpigmented shading along mantle and foot wall join, black pigmentation darkest over centre of cephalic folds; mantle narrow, edge thickened, weakly lobed without black pigmentation; pneumostomal lobe under mantle, narrow and unpigmented.

Shell ( Figs 68F–J; Table S9). Small to medium sized (max sl mean = 15.1 mm, SD = 2.4 mm, n = 5), ovate; height low to medium; apex offset strongly posterior and left pointing to posterior, apical sides convex, protoconch direction homostrophic (n=3, Fig. 68J), shell whorl dextral; growth striae notable uneven, shell thin, rib count (mean = 41, SD = 5.7, n = 5), primary ribs white, fairly straight, increasingly widen to shell lip, weakly extend beyond shell lip; interstices pale brown to black,; secondary ribs indistinct and fewer than primary; paired primary ribs on siphonal ridge, more prominent than other primary ribs; dark patches with 3–4 secondary ribs either side of siphonal ridge. Interior shell margin and spatula dark chocolate brown to black, primary and secondary ribs marked by short white rays often extending over shell margin, siphonal groove distinct and weakly bent; shell edge scalloped, not corrugated, swollen rounded; ADM scar distinct, CMS straight, paler than shell lip. Thickening and dark brown /black of shell lip common.

Reproductive system ( Fig. 69E; n = 1). Positioned within right side of coelom, against foot wall on foot muscle, under the respiratory cavity; epiphallic parts lie over back of BM; GA very small, singular GP through foot wall; AO very small elongate, tip blunt; ED relatively large, broad, bent, joins to side of GA; single flagellum (F1) long broad, as long as ED, appears as an extension of ED; GA, AO, ED all white muscular fibrous tissue; EG large, soft whitish tissue, slightly folded; BD and CD short, broad, jointly connect into upper end of GA; BD without any distal loop, longer slightly narrower than CD; both ducts smooth featureless, pass closely together through outer side of RAM ( BD over CD) into folded, soft white tissues of large MG complex; BC very large, bulbous, thin translucent test, embedded in MG folds close to embedded SV; HD large, coiled, links AG to small yellowish granulated HG; AG larger than HG, sides match curvature of inner foot wall.

Spermatophore ( Fig. 69F). Body cylindrical, relatively short (length = 3.68 ± 0.87 mm, n = 2); test thin, translucent; head bulbous, tip bluntly rounded, wide, evenly cylindrical, containing a core white gelatinous mass, tapers along the transparent flagellum to a thin tip; both sections smooth, featureless. Head section slightly shorter but much wider than flagellum (head length = 1.95 ± 0.37 mm, ~ 55% of SPM length; head width = 119 ± 8 μm, flagellum width = 13 ± 0.0 μm, n = 2); 6 SPM tightly coiled in one bursa embedded in brown gelatinous mass.

Comparative remarks. In our mitochondrial phylogeny, S. bourailensis sp. nov. ( atra group, unit 49) is the sister species of S. ouassensis sp. nov.; for comparison refer to comparative remarks under that species. We found S. bourailensis sp. nov. in sympatry with seven congeners in NC and on Lifou, Loyalty Islands: For comparison with S. atra (unit 41), S. hienghenensis sp. nov. (unit 40), S. monticulus (unit 57), S. normalis (unit 14), S. ouasseensis sp. nov. (unit 48), S. caledonica sp. nov. (unit 23), and S. viridis (unit 25) refer comparative remarks under these species. Specimens of S. bourailensis sp. nov. on Lifou slightly differ from those on NC in having a smaller shell with wider and fewer primary ribs and a golden-brown internal colouration.

Distribution and habitat

Recorded as endemic to NC and Lifou ( Fig. 70). In this study, found on exposed to sheltered rocky boulder and platform shores, mid to upper littoral levels (amongst and above oysters) ( Fig. 68P).

Etymology

Named after type locality of Bonhomme du Bourail, NC.