Siphonaria nusalikensis, 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 : 168

Siphonaria nusalikensis sp. nov.

( Figs 63L , 64E )

Material examined. Type material. Holotype, from NW side of Big Nusa Island , 02°34,1’S, 150°46,7’E, New Ireland, PNG; coll. KAVIENG 2014 expedition, KM21, 28 Jun. 2014 ( MNHN IM-2013-55334 [M532], Fig. 63L ).

External morphology (preserved). Foot sole, foot wall, cephalic folds and pneumostome cream, paler to foot edge; mantle translucent, edge thickened strongly lobed with dark/black pigmentation on mantle edge aligning with rib interstices, faint pigmentation over cephalic folds.

Shell ( Fig. 63L ; Table S9). Small sized (max sl = 4.76 mm, n = 1), circular ovate, height tall; apex weakly offset to posterior and left, apical sides convex except posterior which is concave; protoconch hooked to posterior, direction heterostrophic (n = 1), shell whorl dextral, shell thin; growth striae indistinct; multiple radial colour bands, protoconch area dark brown, central bands pale to dark, shell fringe pale brown; rib count (29, n = 1), predominance of primary ribs, few secondary ribs, weakly raised, off white and rounded, broaden to shell edge; paired primary ribs form siphonal ridge, ribs ends protrude weakly at shell lip, shell edge weakly scalloped and corrugated; rib interstices indistinct, darker. Interior shell margin to spatula mottled dark chocolate brown; outer shell margin paler with light brown rays aligning under ribs; siphonal groove distinct, same colour as spatula, darker than margin; ADM scar indistinct, CMS convex; no thickening of shell lip noted.

Reproductive system ( Fig. 64E; n = 2). Positioned within right side of coelom, against foot wall on foot muscle, under the respiratory cavity; epiphallic parts positioned between RAM and BM. GA small, with singular GP through foot wall; AO small, bulbous, tip blunt, joined to upper GA; ED (incomplete) broad, joins to side of AO and GA; GA, AO, ED all white muscular fibrous tissue; BD and CD connect closely together into GA below AO junction, both long, narrow, slightly bent, pass closely together outside RAM ( BD over CD) into soft white folded tissues of MG; BD smooth, featureless; CD with short lobed mid-section; CD connecting to large MG / AG complex; BC relatively small, elongate, thin whitish translucent test, embedded in MG / AG folds close to embedded SV; BD without distal loop or MA; HD small, coiled, links ducts in soft white folded tissues of AG to yellowish granulated HG; outer edge of MG lobed; AG larger than HG, sides match curvature of inner foot wall.

Comparative remarks. In our mitochondrial phylogeny ( Figs 1 , 3 ), S. nusalikensis sp. nov. ( plicata group, unit 89) is the sister species of a clade comprising S. guamensis (unit 70) and an unidentified species from Rarotonga known only from one DNA sequence (unit 17). Siphonaria nusalikensis differs from these species by genetic distances in COI of 11% ( S. guamensis ) and 13.3% (unit 17) (Table S7). We found S. nusalikensis sp. nov. in sympatry with three congeners at New Ireland, PNG: For comparisons with S. normalis and S. viridis refer to comparative remarks under these species. Siphonaria recurva sp. nov. differs in having a larger shell with a less offset apex, a more prominent siphonal ridge and stronger edge scalloping, a similar BD, but with distal loop and a larger BC.

Distribution and habitat. Recorded as exclusive to Nusalik Island (Big Nusa Island), Kavieng, PNG ( Fig. 67 ). In this study, found on rocky shores, intertidal.

Etymology. Named after the type locality of Nusalik Island (Big Nusa Island), Kavieng, PNG.

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.