Siphonaria hienghenensis, 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 : 156-157

Siphonaria hienghenensis sp. nov.

( Figs 57I–L, Q–R, 59I–J)

Siphonaria ‘ atra group, unit 40’— Dayrat et al. 2014: 264 (in part)

Material examined. Type material. Holotype, from Ponerihouen, 21°05.644’S, 165°26.646’E, NC; coll. B.W. Jenkins, NC03-1, 23 Oct 2018 ( AM C.584989 [SK127], Fig. 57I). 27 paratypes, same data as holotype ( AM C.585524 20+p, C.584985 p [M355], Fig. 57J, C.584986 p [M357], C.584987 p [M358], C.584988 p [M378], C.584990 p [SK170], Fig. 57K, C.584991 p [SK362]); paratye from Ouassé nr Canala, 21°30.346’S, 166°03.732’E, NC; coll. B.W. Jenkins, NC02-1, 22 Oct 2018 ( AM C.584805 p [M375], Fig. 57L).

Other, non-type material. NC: Hienghène, 20°41.210’S, 164°59.108’E NC04-1 ( AM C.584808 p); Ouassé nr Canala, 21°30.346’S, 166°03.732’E, NC02-1 ( AM C.585968 10+p); S of Pouebo NC04- 2 ( AM C.585399 7p); Presqu’ile de Ouano La Foa 20°51.434’S, 165°48.479’E NC06-4 ( AM C.584816 3p); Presq’ile Ducos Baie des Dames Noumea 22°14.170’S, 166°24.524’E NC01-1 ( AM C.584803 16p) .

External morphology ( Fig. 57Q). Foot sole, foot wall, mantle evenly pale grey, paler to foot edge; no pigmentation; mantle covers shell lip, wide, edge thickened lobed, paler grey; pneumostome lobe large, under mantle.

Shell ( Figs 57I–L; Table S9). Medium sized (max sl mean = 19.8 mm, SD = 1.9 mm, n = 7), ovate to elongate; height medium to low; apex offset central, apical sides strongly convex, protoconch direction undetermined, shell whorl dextral; growth striae prominent in bands, shell thickness thick; 3 radial band layers: whitish protoconch, mid shell dark brown band, and mid shell to edge pale brown/grey band; growth lines indistinct; rib count (mean = 45, SD = 6.5, n = 7), primary ribs pale white, fairly straight, ridges rounded, increasingly raised to and slightly protrude beyond uneven shell lip; shell lip scalloped between primary ribs; paired primary ribs form siphonal ridge which protrudes up to 1 mm beyond shell lip; secondary ribs similar to primary ribs, rib interstices slightly darker, indistinct. Interior margin irregular brown patterns; underside of primary ribs furrowed, white to cream rays, rib interstices marked with dark brown rays, some rays extend from spatula to shell lip; spatula dark chocolate brown, maybe white in smaller/juvenile specimens; siphonal groove distinctly furrowed, fairly straight bounded by dark brown patches; ADM scar distinct white to brown, paler than spatula and margin, CMS straight, paler than shell lip; Internal shell thickening occurs in larger/more mature specimens; shell lip thickens, whitens with yellow tinge, infills and reduces lip scalloping, spatula becomes whitened, distinct dark brown patches remain prominent on both sides of the siphonal groove. Significant colour and sculpture variation exists in the shell of this species.

Reproductive system ( Fig. 59I; n = 5). Overall very small; hermaphroditic ( HG, AG and MG) complex ( AL = 12.52mm) on right side within coelom against inside of foot muscle and foot wall under the respiratory cavity and intestine; epiphallic parts beside BM and RAM; GA very small; AO very large, elongated, bluntly bulbous, joins to GA, singular GP; ED relatively short, broad, smaller than AO, joins to side of GA; GA, AO, ED all white muscular fibrous tissue; EG soft whitish, slightly folded, smaller than AO, single short blunt flagellum (F1); BD and CD jointly but opposing connections to GA between ED, AO and GP; BD narrow short with a prominent distal loop without any MA; CD broad short; both ducts smooth and pass closely together through RAM ( BD over much broader CD); CD connects into MG; BD connects to small BC with thick white test, embedded in mid folds of MG / AG close to SV; HD short, narrow, coiled, links AG to a larger yellowish granulated HD; MG and AG small, folded, soft white tissue. Spermatophore ( Fig. 59J). Relatively short (length = 5.69 ± 0.99 mm, n = 2) and narrow; test thin, translucent, containing a white gelatinous core mass; over half-length comprises a translucent bulbous cylindrical body section (head length = 3.01 ± 1.18 mm, ~ 63% of SPM length, n = 3), tip bluntly pointed, tapering into a filamentous transparent flagellum; head section much thicker than flagellum (head width = 72 ± 29 μm, n = 3; flagellum width = 13 ± 3 μm), both sections smooth, featureless; 2 SPM tightly coiled in single BC ( AM C.584989).

Comparative remarks. In our mitochondrial tree ( Figs1, 2, Clade G), unit40 ( atra group)is the sister lineage of S. atra (unit 41). Unit 40 contains S. hienghenensis sp. nov. and sequences from Qld and PNG that probably represent an undescribed species. These sequences are excluded from S. hienghenensis sp. nov. delimited here. Siphonaria hienghenensis sp. nov. differs from S. atra by COI distances of ≥ 8.3%. The next more closely related species is S. alba (unit 39), which differs by COI distances of ≥ 13% (Table S3). Siphonaria hienghenensis sp. nov., considered to be endemic to New Caledonia, has been found in sympatry with four species in NC: For comparisons with S. monticulus and S. normalis refer to comparative remarks under these species. Siphonaria ouasseensis sp. nov. has a smaller, taller, darker shell with more raised and broader ribbing, BD with a bursal loop and a narrower F1. Siphonaria bourailensis sp. nov. has a smaller, taller, paler shell with more uneven ribbing, darker interior, a larger pointed AO, and a shorter SPM. Six are sympatric on NC. Siphonaria caledonica sp. nov. has a smaller, taller, darker shell with stronger edge scalloping and darker interior, and a larger pointed AO and ED. Siphonaria poindimiensis sp. nov. has a smaller, taller, darker shell with stronger edge scalloping and darker interior, and a larger pointed AO. Siphonaria namukaensis sp. nov. has a smaller, slightly darker shell with more raised ribbing, weaker edge scalloping, and a smaller, narrower AO, Siphonaria poindimiensis sp. nov. has a taller shell with stronger edge scalloping, wider ribs, fused dual siphonal ridge ribs, patterned interstices, a larger AO, and a longer ED. For comparisons with S. viridis and S. atra refer to comparative remarks under these species.

Distribution and habitat. Recorded as endemic to NC and Lifou ( Fig. 60). In this study, found on exposed to sheltered rocky boulder and platform shores, mid and upper littoral levels ( Fig. 57R).

Etymology. Named after Baie de Hienghène, immediately north of the type location of Ponerihouen, west coast of NC, Pacific Ocean.