Siphonaria namukaensis, 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 : 164-167

Siphonaria namukaensis sp. nov.

( Figs 65A–F, M–N, P; 66A–D)

Siphonaria ‘ laciniosa group, unit 22’— Dayrat et al. 2014: 261 (in part).

Material examined. Type material. Holotype, from Namuka Bay , 18°08.094’S, 177°23.490’E, Viti Levu, Fiji; coll. B.W. Jenkins, FI02-2, 23 Aug 2018 ( AM C.585826 [M282], Fig. 65A). 25+ paratypes, same data as holotype ( AM C.585893 20+p, C.584857 p [M278], C.584858 p [SK109], Fig. 65B, C.585823 p [M279], C.585824 p [M280], Fig. 65C; C.585825 p [M281], Fig. 65D).

Other, non-type material. Fiji, Viti Levu: Vuda Point Marina seawall, 17°40.878’S, 177°23.009’E, FI03-2 ( AM C.585391 10+p, C.585696 8p, C.585828 p [M283], C.585829 p [M284], C.585830 p [M285], C.585831 p [M422], C.584864 p [M422, SK110], C.584865 p [SK116]); Heal of foot First Landing, 17°40.753’S, 177°23.006’E, FI03-1 ( AM C.585827 p [M290]); Namuka Bay 18°08.094’S, 177°23.490’E, FI02-2 ( AM C.586006 20+p, C.584856 p [M277], C.584858 p [SK109]); nr Tagaqa, S. coast of Viti Levu, 18°11.802’S, 177°38.640’E FI02-1 ( AM C.585822 p [M276]) . NC: Poindimie 21°55.901’S, 165°19.672’E, NC03-2 ( AM C.584994 p [M455, SK193], C.585000 p [M461, SK194], Fig. 65F); Poum 2, 20°13.754’S, 164°01.699’E, NC05-3 ( AM C.585999 5p) .

External morphology ( Fig. 65M). Foot sole evenly dark grey; foot edge, foot wall, cephalic folds and pneumostomal lobe yellow grey; mantle wider than foot wall, thin translucent, edge thickened, weakly lobed, yellow band; irregular blotches of dark pigmentation on foot wall, cephalic folds, fading to mantle join; pneumostome elongated.

Shell ( Figs 65A–F, P; Table S9). Small to medium sized (max sl mean = 14.6 mm, SD = 3.7 mm, n = 7), circular ovate; height medium; apex offset central, apical sides convex, protoconch direction homostrophic (n = 2, Fig. 65P), shell whorl dextral; growth striae prominent; rib count (mean = 52.4, SD = 6.5, n = 7), ribs fairly straight, rib ridges slightly raised, rounded, align with uneven and weakly scalloped shell edge; interstices narrow, black; primary and secondary ribs white, very similar in size, brown flecks and 1–2 secondary ribs in spaces between primary ribs; siphonal ridge sole rib fold, formed by 3–4 close primary ribs. Interior shell lip tan to whitish, shell margin golden dark brown to tan, white rays align on shell margin under primary/secondary ribs, prominent siphonal groove and spatula pale tan to whitish;ADM scar prominent, darker than shell lip, margin and shell edge; CMS straight; thickening and whitening of shell lip occurs.

Reproductive system ( Figs 66A, C; n = 5). Positioned within right side of coelom, against foot wall on foot muscle, under the respiratory cavity; epiphallic parts positioned over BM. GA small, with singular GP through foot wall; AO large, broad, bent, bluntly pointed, joined to lower ED and upper GA; ED very short, very broad, centrally bent, joins to side of GA; GA, AO, ED all white muscular fibrous tissue; EG very large, soft whitish tissue, slightly folded, joins ED; extension joins in parallel to single narrow flagellum (F1), similar width to ED, appears as an extension of ED, possible F2 narrow short; BD and CD connect in opposing directions closely into GA between ED join and GP, both ducts short, slightly bent, smooth, thickened, whitish, featureless, pass closely together inside outer RAM ( BD over wider CD) into soft white folded tissues of MG; MG / AG complex large; CD connecting to ducts, BC embedded in folds close to embedded SV; BD with distal loop and MA; BC relatively small, spherical, thin whitish translucent test; HD short, narrow, coiled, links ducts in soft white folded tissues of AG to yellowish granulated HG; outer edge of MG lobbed; AG larger than HG, sides match curvature of inner foot wall.

Spermatophore ( Figs 66B, D). Long, thread-like (length = 8.76 mm, n =1), translucent, test thin; head section bluntly rounded, evenly cylindrical, centrally bent, contains a core white gelatinous mass, tapers along the transparent and narrower flagellum (head length = 3.66 mm 42% of total length; head width = 103 μm, flagellum width = 17 μm, n = 1); both sections smooth, featureless. SPM tightly coiled embedded in purple/brown gelatinous mass in BC (3 SPM in AM C.585826, Fig. 66B, 1 SPM in AM C.585822, 5 SPM in AM C.585831, 1 SPM in AM C.584994, Fig. 66D).

Comparative remarks. In our mitochondrial phylogeny ( Figs 1, 3), S. namukaensis sp. nov. ( laciniosa group, unit 22) is the sister species of S. yagasaensis sp. nov. (unit 67). Both species are well-differentiated from each other by COI distances of ≥ 17%. From all other congeners S. namukaensis differs by COI distances of ≥ 18% (Table S6).

Throughout its range, we found S. namukaensis sp. nov. in partial sympatry with six congeners. For comparisions with S. atra and S. normalis refer to comparative remarks under these species. Siphonaria vudaensis sp. nov. has a larger, lower, darker shell with stronger edge scalloping, and darker interior, a blunter AO. Siphonaria poindimiensis sp. nov. has a smaller taller darker shell with stronger edge scalloping, a larger AO and ED. Siphonaria tagaquensis sp. nov. has a smaller taller darker shell, a longer ED. Siphonaria poindimiensis sp. nov. has a taller, darker shell with broader ribs and stronger edge scalloping, and wider ribs, a larger BC and a longer, wider ED.

Distribution and habitat. Recorded from Viti Levu, Fiji and E coast NC, Pacific Ocean ( Fig. 67). In this study found at sheltered positions on exposed and moderately exposed rocky shores, upper and mid littoral ( Fig. 65N).

Etymology. Named after the type locality of Namuka Bay, Viti Levu, Fiji.