Siphonaria jiigurruensis, 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 : 158-159

Siphonaria jiigurruensis sp. nov.

( Figs 61A–E, 62B–C)

Siphonaria ‘ laciniosa group, unit 21’— Dayrat et al. 2014: 267, fig. 4C.

Material examined. Type material. Holotype, from Lizard Island 14°40.908’S, 145°27.007’E, Qld, Australia; coll. B.W. Jenkins, Q40-1, 29 June 2017 ( AM C.584789 [M423, SK114 ( RS, SPM)], Fig. 61A). Five paratypes, same data as holotype ( AM C.585641 4p, C.585496 p [M398], Fig. 61C); two paratypes from Freshwater Beach, Lizard Is, Qld; coll. P.H. Colman, 2 Dec. 1974 ( AM C.585032 p [SK264], Fig. 61B, C.608197 p [SK400], Fig. 61E). Other, non-type material. Australia, Qld: Freshwater Beach, Lizard Is, 14°39.922’S, 145°26.854’E ( AM C.585943 20+p).

External morphology. Foot sole, foot wall, cephalic folds and pneumostomal lobe evenly light grey; foot sole darker to centre, paler to edge; fringing mantle narrow translucent at foot wall gradually becoming opaque with a thickened paler grey band at the lobed mantle edge, black pigmentation markings on band aligning with rib interstices; genital pore inconspicuous, located on foot wall to right anterior of right cephalic fold; two small black epithelial eye spots centralised on two thick centrally touching dark grey cephalic folds; thin pale grey pneumostomal lobe part of the mantle, between the right ADMs, closes the pneumostome and anus at the mantle edge.

Shell ( Figs 61A–C, E; Table S9). Small sized (max sl mean = 15.3 mm, SD = 2.7 mm, n = 3), elongate ovate; height tall;apex offset central weakly posterior, apical sides weakly convex, protoconch direction homostrophic (n = 1, Fig. 61E), shell whorl dextral; growth striae prominent, 3 prominent coloured bands—protoconch area whitish, mid dark brown/black, margin and shell lip light brown; shell thick; rib count (mean = 43, SD = 5.0, n = 3), 8–10 primary ribs whitish, ridge rounded, fairly straight raised, weakly extend beyond slightly scalloped corrugated uneven shell lip; paired primary ribs on siphonal ridge, no more prominent than other primary ribs; few secondary ribs, rib interstices darker. Interior even white rays align on shell margin under primary/secondary ribs, brown rays under rib interstices, spatula dark brown or whitish; dark brown shell margin dark brown to tan, siphonal groove distinct, same colour as shell edge, points to right anterior; spatula dark chocolate brown to mottled tan even whitish; ADM scar distinct, CMS weakly convex. Degree of intraspecific variability low. Conchologically very similar to S. viridis in northern Qld to WA, Australia.

Reproductive system ( Fig. 62B; n = 1). Positioned within coelom under the respiratory cavity, occupies the right side of coelom, hermaphroditic glands positioned to posterior against right foot wall and over foot sole, epiphallic parts positioned to anterior between BM and RAM; GA medium, with singular GP through foot wall; AO large, elongated, broad, rounded point, joins next to ED to upper GA; ED short, broad, coiled; GA, AO, ED all white muscular fibrous tissue; EG reasonably large, soft whitish tissue, slightly folded, joins ED; single elongated narrow flagellum (F1), appears as an extension of similar length and broader ED. BD and CD connect side-by-side into GA between ED / AO joint and GP, both ducts smooth, thickened, whitish, featureless, pass closely together through RAM ( BD over CD) into soft white folded tissues of MG; MG / AG complex relatively large; BC embedded in folds of AG / MG close to embedded SV; BD with distal loop, posteriorly short and without prominent MA, similar thickness to CD; BC relatively large, bulbous, 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 ( Fig. 62C). Thread-like (length = 6.73 mm, n =1), translucent, test thin; head section bluntly rounded, evenly cylindrical, containing a white gelatinous core, tapers along the transparent flagellum to a thin tip; both sections smooth, featureless. Head section longer wider than flagellum (head length = 4.15 ± 0.34 mm, n = 2; ~ 58% of SPM length, head width = 85 ± 24 μm, n = 2, flagellum width = 34 ± 16 μm); 5 SPM tightly coiled embedded in brown gelatinous mass in single BC ( AM C.584789).

Comparative remarks. In our molecular phylogeny ( Figs 1, 3), S. jiigurruensis sp. nov. ( laciniosa group, unit 21) forms a well-differentiated lineage. The species differs from other species by COI distances of ≥ 23% (Table S6). We found S. jiigurruensis sp. nov. in sympatry with four congeners on Lizard Island, Qld: For comparisons with S. normalis , S. oblia , S. atra , and S. viridis refer to comparative remarks under these species. The specimen figured as ‘ laciniosa group, unit 21’ in Dayrat et al. (2014: 262, fig. 4C) corresponds well with S. jiigurruensis sp. nov.

Distribution and habitat. Recorded exclusively from Lizard Island, northern Qld, Australia ( Fig. 60). In this study, found on granite boulder/platform exposed rocky shores, mid to upper littoral levels (above barnacle zone) ( Fig. 61D).

Etymology. For Jiigurru, the name of Lizard Island in the language of the Dingaal people, traditional custodians of the land.