Siphonaria mauiensis, 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 : 162-164

Siphonaria mauiensis sp. nov.

( Figs 63G–K , 64A–B )

Material examined. Type material. Holotype, from Hanakao’o Beach 20°54.586’N, 156°41.338’W, Maui, Hawaii; coll. B.W. Jenkins, HA03-2, 23 June 2018 ( AM C.584888 [M297], Fig. 63G ). Six paratypes, same data as holotype ( AM C.584890 p [SK245], Fig. 63I , C.584891 p [SK207], Fig. 63H , C.585586 3p, C.584921 p [SK206]).

External morphology ( Fig. 63K ). Foot sole grey; foot wall, mantle, cephalic folds, pneumostome evenly yellowish/green; irregular blotches of black pigmentation on foot wall, concentrated over cephalic lobes and posterior; mantle translucent narrower than foot wall, covers exposed inner shell lip, wider at anterior, mantle edge thickened white band lobed with even black pigmentation rays 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 between the right ADMs.

Shell ( Figs 63G–I ; Table S9): small sized (max sl mean = 11.93 mm, SD = 1.16 mm, n = 3), circular ovate; height tall; apex offset central, apical sides convex uneven, protoconch direction homostrophic to central (n=1), shell whorl dextral, apex weakly hooked; growth striae distinct, 2–3 discontinuous bands of blue/grey radial shading, protoconch area dark brown, shell thin; rib count (mean = 60, SD = 4.3, n = 3), ribs white/grey, rib interstices narrow brown/black, difference between primary and secondary ribs indistinct, narrow, crooked, weakly raised, slightly broaden to and weakly protrude beyond uneven shell lip; siphonal ridge indistinct formed by 3–4 ribs. Interior shell margin mottled brown, shell lip dark brown with uneven white rays extending to shell margin under ribs; siphonal groove distinct, same colour as shell edge but maybe white; spatula dark chocolate brown; ADM scar distinct, CMS straight; thickening of shell lip occurs in mature specimens, infills and reduces scalloping of lip, spatula becomes whitened.

Reproductive system ( Fig. 64A; n = 1). Positioned within right side of coelom, against foot wall on foot muscle, under the respiratory cavity; RS very large proportion of animal size compared to other species; epiphallic parts ( GA, EG and ED) positioned over back of BM, F1 long, draped over BM; GA small, with singular GP through foot wall; AO medium, bluntly rounded, joined at base to upper GA, rests against MG; ED long broad, centrally bent, joins to posterior side of GA; GA, AO, ED all white muscular fibrous tissue; EG very large, soft whitish tissue, folded, joins ED; single long broad flagellum (F1) centrally looped, appears as an extension of wider ED; BD and CD connect closely in opposite directions into GA between ED join and GP, both ducts whitish curved, pass closely together around outside of RAM ( BD over CD) into soft white folded tissues of MG / AG complex; outer edge of CD lobed, broadens to connection with AG ducts, BC long with distal loop and MA to inner foot wall in front of BM, initially broader than CD, narrows to embed in folds of AG; BC relatively large bulbous thin whitish translucent test, 2 SPM in BC (n=1); HD short broad coiled, links ducts in soft white folded tissues of AG to orange granulated small HG; outer edge of MG lobbed; AG much larger than HG, outer sides of both reflect curvature of inner foot wall.

Spermatophore ( Fig. 64B ). Relatively long and thin; test thin, translucent, comprises a translucent cylindrical body section containing a white gelatinous thread-like core, tapers into a filamentous transparent flagellum (head length = 24.56 mm, n = 1; flagellum incomplete), head section thicker than flagellum (head width = 148 μm, flagellum width = 74.1 μm, n = 1); head tip bluntly rounded; both sections smooth, featureless; 2 SPM tightly coiled, embedded in brown gelatinous mass within BC ( AM C.584888).

Comparative remarks. Siphonaria mauiensis sp. nov. ( plicata group, unit 60) forms a well-differentiated lineage in the mitochondrial tree ( Figs 1 , 3 ). It differs from other species by COI distances of ≥ 29.6% (Table S7). We found S. mauiensis sp. nov. in sympatry with two congeners in Hawaii. For comparisons with S. normalis and S. nuttallii refer to comparative remarks under these species. Along with the latter, S. undans sp. nov. (unit 61) and S. waikoloaensis sp. nov. (unit 55) are other Hawaiian species of the plicata group, but they are genetically highly distinct.The shell of S. mauiensis sp. nov. resembles that of S. lirata from Guam, but has a consistently darker interior.

Distribution and habitat. Recorded exclusively from Hanakao’o Beach, Maui, Hawaii, USA ( Fig. 67 ). In this study, found in sheltered positions (mainly rock crevices) on moderately exposed fine-algal covered rocky basalt shores, upper littoral level ( Fig. 63K ).

Etymology. Named after the type locality’s island of Maui, Hawaii.

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 3. Maximum Likelihood phylogram (partial, species not collapsed). Clades J–L (laciniosa and plicata groups) 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 (see Tables 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 63. Shells of S. madangensis sp. nov., S. maloensis sp. nov., S. mauiensis sp. nov., S. nusalikensis sp. nov. and S. cacao sp. nov. A–B. S. madangensis sp. nov. A. Holotype MNHN IM-2013-12006 [M550]. B. Paratype IM-2013-13132 [M552]. C–F. S. maloensis sp. nov. C. Holotype IM-2007-31454 [M545]. D. Paratype IM-2007-31358 [M546], Sek Is. E. Paratype IM-2007- 31355 [M547], Palikulo Peninsula. F. Paratype IM-2007-31353 [M548], Palikulo Peninsula. G–K. S. mauiensis sp. nov., Maui, Hanakao’o Beach. G. Holotype AM C.584888 [M297, SK208]. H. Paratype AM C.584891 [SK207]. I. Paratype AM C.584890 [SK245]. J. Animal. K. In situ. L. Holotype of S. nusalikensis sp. nov. IM-2013-55334 [M532]. M–O. S. cacao sp. nov., French Polynesia, Tubuai. M. Holotype IM-2007-35319 [SK506]. N–O. Paratypes IM-2007-35317/18. Unlabelled scale bars = 10 mm.

FIGURE 64. Reproductive morphology of S. mauiensis sp. nov., S. madangensis sp. nov., S. nusalikensis sp. nov. and S. cacao sp. nov. A–B. Holotype of S. mauiensis sp. nov. AM C.584888 [M297, SK208]. C–D. S. madangensis sp. nov. Paratype MNHN IM-2013-13132 [M552, SK507], PNG, Sek Is. E. Holotype of S. nusalikensis sp. nov. MNHN IM-2013-55334 [M532]. F–G. Holotype of S. cacao sp. nov. MNHN IM-2007-35319 [SK506, EPI part only). Unlabelled scale bars = 1 mm.

FIGURE 67. Known occurrence records of S. madangensis sp. nov., S.maloensis sp.nov., S. mauiensis sp. nov., S.namukaensis sp. nov., S. nusalikensis sp. nov. and S. cacao sp. nov.