Siphonaria ouasseensis, Jenkins, Bruce & Köhler, Frank, 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 : 169

Siphonaria ouasseensis sp. nov.

( Figs 65G–I, Q–R , 66E–H )

Material examined. Type material. Holotype, from Ouassé , nr Canala, 21°30.346’S, 166°03.732’E, NC; coll. B.W. Jenkins, NC02-1, 22 Oct 2018 ( AM C.584786 p [M377, SK328], Fig. 65G ). Six paratypes, same data as holotype ( AM C.584800 p [SK344], Fig. 65H , C.584908 p [SK341], C.585732 p [SK343], C.585923 d [SK346], Fig. 65I , C.585924 p [SK342], C.585993 p [SK347], Fig. 65Q ).

External morphology. Foot sole, foot wall, cephalic folds and pneumostome cream, paler to foot edge; mantle translucent narrow, wider anteriorly, edge thickened strongly lobed with cream/white band; faint dark/black pigmentation on mantle edge aligning with rib interstices, dark pigmentation over centre of cephalic folds.

Shell ( Figs 65G–I, Q ; Table S9): Small (max sl mean = 13.5 mm, SD = 1.02 mm, n = 6); ovate, often elongated, shape irregular, height medium; apex weakly offset sightly posterior and left, apical sides convex, protoconch direction weakly heterostrophic (n = 1, Fig. 65Q ), shell whorl dextral; growth striae indistinct, shell thick; rib count (mean = 35, SD = 2, n = 6), exterior uneven, radial shading bands faint, protoconch area pale; primary ribs white, secondary ribs darker, variably raised, crooked and bent, narrow and uneven in width, ridge rounded, extend unevenly slightly beyond shell lip to scallop and corrugate the shell edge; ribs unevenly spaced, 2–3 primary ribs form raised siphonal ridge; variable number secondary ribs between primary ribs, most rib interstices dark brown. Interior evenly dark, chocolate-brown, sometimes mottled paler in places, short white rays on shell margin align under primary/secondary ribs, siphonal groove distinct; ADM scar distinct, CMS straight, thickening and whitening of shell lip apparent in some specimens.

Reproductive system ( Figs 66E, G; n = 3). Positioned within right side of coelom, against foot wall on foot muscle, under the respiratory cavity and digestive glands; epiphallic parts all white muscular fibrous tissue, reduced in size and positioned over BM (F1 looped over front of BM), singular GP through foot wall; GA small indistinct; AO relatively small broad, bluntly pointed (embedded in folds of MG), joined to upper GA; ED elongated broad thickened, centrally twisted, joins to upper GA; EG small, soft whitish tissue, folded joins ED; single long narrow bent flagellum (F1) as an extension of ED, of similar length. BD and CD connect in opposing directions into GA between ED join and GP, both ducts very narrow long straight smooth whitish, pass together through RAM ( BD over thicker CD) into soft white folded tissues of MG; BC embedded in folds of AG / MG; BD with prominent distal twisted loop with MA attached to inner anterior foot wall above BM, bent immediately before BC; BC small bulbous, thin whitish translucent test; MG / AG complex relatively large, often separated ( Fig. 66E, G ); HD thickened, brown markings, small coils, links ducts in soft white folded tissues of AG to yellowish granulated reddish spotted HG; HG larger than AG / MG.

Spermatophore ( Fig. 66F, H ). Test thin, translucent (length = 9.62 ± 0.08 mm, n = 2), head evenly cylindrical, tip bluntly rounded, containing a white gelatinous core, tapers along the transparent flagellum to a thin tip; both sections smooth, featureless; head wider and longer than flagellum (head length = 6.06 ± 1.11 mm, ~ 72% of SPM length, head width = 103 ± 0 μm, flagellum width = 17 ± 0 μm, n = 2). 5 SPM tightly coiled and embedded in dark brown gelatinous mass in one BC.

Comparative remarks. In our mitochondrial tree ( Figs 1 , 2 ), S. ouasseensis sp. nov. ( atra group, Clade H, unit 48) forms a clade with S. bourailensis sp. nov. (unit 49), S. pravitas sp. nov. (unit 51) and S. scabra (unit 50) ( Figs 1 , 2 ). It differs from S. bourailensis sp. nov. by COI distances of ≥ 11.8% and from other species by COI distances of ≥ 24% (Table S4). We have found this species in sympatry with three congeners in NC: Siphonaria bourailensis sp. nov. has fewer and broader ribs, a more prominent siphonal ridge, a larger, wider and pointed AO, and a larger ED. For comparisons with S. hienghenensis sp. nov. and S. atra refer to comparative remarks under these species.

Distribution and habitat. Known only from NC ( Fig. 70 ). In this study, found at Ouassé nr Canala in sheltered positions on exposed and sheltered rocky boulder and platform shores, mid to upper littoral level ( Fig. 65R ).

Etymology. Named after the type locality of Ouassé near Canala, NC.

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 65. Shells of S. namukaensis sp. nov., S. ouasseensis sp. nov. and S. caledonica sp. nov. A–F, M–N, P. S. namukaensis sp. nov. A–E, M–N, P. Fiji. A. Holotype AM C.585826 [M282]. B. Paratype AM C.584858 [SK109]. C. Paratype AM C.585824 [M280]. D. Paratype AM C.585825 [M281]. E. Tagaqa, AM C.585822 [M276]. F. NC, Poindimie, AM C.585000 [M461, SK194]. M. Animal. N. In situ. P. Protoconch, Vuda Point, AM C.584864 [M422, SK110]. G–I, Q–R. S. ouasseensis sp. nov., NC, Ouassé. G. Holotype AM C.584786 [M377]. H. Paratype AM C.584800 [SK344]. I. Paratype AM C.585923 [SK346]. Q. Protoconch, AM C.585993 [SK347]. R. In situ. J–L, O, S–T. S. caledonica sp. nov. J. Holotype AM C.584788 [M364], NC, Tiari. K. Paratype AM C.585015 [M366], La Roche Percee. L. Paratype AM C.585838 [M362]. O. In situ, Tiari. S. Animal. T. Protoconch, AM C.585839 [M363]. Unlabelled scale bars = 10 mm.

FIGURE 66. Reproductive morphology of S. namukaensis sp. nov., S. ouasseensis sp. nov. and S. caledonica sp. nov. A–D. S. namukaensis sp. nov. A. Paratype AM C.584858 [SK109], Fiji. B. Holotype AM C.585826 [M282], Fiji. C–D. NC, Poindimie, AM C.584994 [M455, SK193]. E–H. S. ouasseensis sp. nov., NC, Ouassé. E. Paratype AM C.585924 [SK342]. F. Paratype AM C.595984 [SK351]. G–H. AM C.585732 [SK343]. I–J. Holotype of S. caledonica sp. nov. AM C.584788 [M364, SK130]. Scale bars = 1 mm.

FIGURE 70. Known occurrence records of S. ouasseensis sp. nov., S. caledonica sp. nov., S. perexigua sp. nov., S. planucosta sp. nov. and S. bourailensis sp. nov.