Siphonaria waikoloaensis, 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 : 192-193

Siphonaria waikoloaensis sp. nov.

( Figs 79D–F, N–O, 80C–D)

Material examined. Type material. Holotype, from Waikoloa Beach , 19°55.456’N, 155°53.491’W, Big Island, Hawaii; coll. B.W. Jenkins, HA04-2, 25 June 2018 ( AM C.584907 [M295, SK214], Fig. 79D) . Paratypes: same data as holotype ( AM C.585327 10+p; Waikoloa Beach 19°55.026’N, 155°53.282’W. HA04-1, 25 June 2018 ( AM C.585327 p [SK254], Fig. 79E; C.584673 p [SK391], Fig. 79F).

Other, non-type material. Hawaii. Big Island: Waikoloa Beach , 19°55.456’N, 155°53.491’W, HA04-2 ( AM C.584906 p [SK206]); 19°55.026’N, 155°53.282’W, HA04-1 ( AM C.595958 2d) .

External morphology. Foot edge, foot wall, cephalic folds and pneumostomal lobe all evenly yellowish/ green, foot sole cream; irregular small blotches of black pigmentation on foot wall and centre of cephalic lobes; mantle translucent narrow thickened edge strongly lobed with bands of black pigmentation aligned with shell rib interstices; genital pore indistinct, located on foot wall to right anterior of right cephalic fold; small black epithelial eye spot centralised on each of centrally touching cephalic folds; pneumostomal lobe under mantle, unpigmented, between the right ADMs.

Shell ( Figs 79D–F, N; Table S9). Small sized (max sl mean = 10.6 mm, SD = 1.4 mm, n = 3), ovate; height tall, shell thin; apex offset weakly posterior and left, apex often hooked/curled to posterior, apical sides strongly convex, protoconch direction homostrophic to central (n = 2, Fig. 79O), shell whorl dextral; 3 radial colour bands, protoconch brownish, central pale brown and outer showing black interstices; rib count (mean = 45, SD = 7.8, n = 3), ~ 12–14 prominent primary ribs, white, crooked, raised, rounded ridges, width broads to shell lip, protrude beyond shell lip with a raised roll to unevenly scallop and corrugate the edge; interstices between primary ribs with 3–4 smaller secondary ribs; paired primary ribs form siphonal ridge, no more prominent than other primary ribs. Interior shell evenly dark chocolate brown, narrow irregular white rays extend from shell lip to margin aligning under primary/secondary ribs, siphonal groove distinct; ADM scar distinct, CMS straight; thickening of shell lip not observed.

Reproductive system ( Fig. 80C; n = 1). Positioned within right side of coelom, against foot wall on foot muscle, under the respiratory cavity; RS proportionally large to animal size compared to other species; epiphallic parts ( GA, EG and ED) positioned in between BM and RAM, GA medium, with singular GP through foot wall; AO medium, bluntly rounded, joined at base to upper GA, rests against MG; ED long broad twisted centrally bent, joins to side of GA and base EG; GA, AO, ED all white muscular fibrous tissue; EG large, soft folded whitish tissue; single long broad flagellum (F1) centrally bent, appears as an extension of much wider ED; BD and CD connect closely in opposite directions into GA between ED join and GP, both ducts narrow whitish curved smooth featureless, pass closely together through outside of RAM ( BD over CD) into soft white folded tissues of MG / AG complex; CD curves and broadens to connect with AG duct, BC long with distal loop and flat MA to inner foot wall, embeds in folds of AG; BC small bulbous thin whitish translucent test, 2 SPM in BC (n=1); HD very small short coiled whitish, links ducts in soft white folded tissues of AG to granulated small HG; AG much larger than HG.

Spermatophore ( Fig. 80D). Relatively short, test thin, translucent,comprises a translucent cylindrical body section containing a white gelatinous thread-like core, tapers into a filamentous transparent flagellum (head length = 8.111 mm n = 1, flagellum incomplete), head section much thicker than flagellum (head width = 185 μm, flagellum width = 74.1 μm n = 1), head tip bluntly rounded; both sections smooth, featureless; 2 SPM tightly coiled, embedded in dark-brown gelatinous mass in holotype.

Comparative remarks. Siphonaria waikoloaensis sp. nov. ( plicata group, unit 55) forms a well-differentiated lineage in the mitochondrial tree ( Figs 1, 3). It differs from other species by COI distances of ≥ 28% (Table S7). We found S. waikoloaensis sp. nov. in sympatry with S. undans on Big Island, Hawaii. For a comparison see under this species.

Distribution and habitat. Recorded from Big Island, Hawaii, USA, Pacific Ocean ( Fig. 78). In this study, found in sheltered positions (mainly rock crevices) on moderately exposed fine-algal covered volcanic-rock shores, at upper littoral level ( Fig. 79N).

Etymology. For the type locality, Waikoloa Beach, Big Island, Hawaii.