Siphonaria costellata, sp. nov.
Creators: name: Jenkins, Bruce
name: Köhler, Frank
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Siphonariida
Siphonariidae
Siphonaria
Siphonaria costellata

description: Siphonaria costellata sp. nov.
(Figs 54K–L, S–T, 58A–B)
Siphonaria guamensis — Tan & Chou 2000: 115, fig 115; Tan & Woo 2010: 61; Tan & Yeo 2010: 294 (not S. guamensis Quoy & Gaimard, 1833).
Siphonaria sp. — Swennen et al. 2001: 142, fig. 522.
Siphonaria ‘ normalis group, unit 13’— Dayrat et al. 2014: 259, 260, 267, fig. 3O.
Material examined. Type material. Holotype, from Lazarus Island, causeway 01°13.288’N, 103°51.195’E, Singapore; coll. Chim C.K. and B.W. Jenkins, SI04-3, 21 Nov 2018 (ZRC. MOL.24890 [M416, SK100], Fig. 54K). 18 paratypes, same data as holotype (AM C.585234 p [M326], AM C.585427 10p, AM C.585677 6p), paratype from Lazarus Island, 01°13.355’N, 103°51.148’E, Singapore; coll. B.W. Jenkins, SI04-2, 24 Nov 2018 (AM C.585226 p [M338], Fig. 54L).
Other, non-type material. Australia, Qld: Weipa, 12°37.795’S, 141°51.853’E, Q52-1 (AM C.585186 p [M075]; C.585187 p [M178]); Inspection Pt, Sweers Is, 17°08.471’S, 139°36.868’E, Q56-3 (AM C.585189 p [M147]). NT: Nhulunbuy, Cape Wirawawoi, 12°09.513’S, 136°46.904’E, NT05-1A (AM C.585529 20+p, C.585075 p [SK044], C.585076p [M028], C.585077 p [M092]); East Woody Islet, 12°09.695’S, 136°45.075’E, NT05- 2 (AM C.585684, 7p); N Turtle Beach, 12°18.816’S, 136°55.930’E, NT04-1 (AM C.585477 17p; C.585990 10+p); Smith Pt 2, 11°07.466’S, 132°08.538’E, NT21- 3 (AM C.585989 10+p). Singapore: Pasir Ris, seawall, 01°22.981’N, 103°56.956’E, SI01-1 (AM C.585986 10p); Fort Road, drain seawall, 01°17.605’N, 103°53.809’E, SI01-3 (AM C.585603 3p); Lazarus Island, 01°13.355’N, 103°51.148’E, SI04-2 (AM C.585988 16p); Lazarus Island causeway, 01°13.288’N, 103°51.195’E, SI04- 3 (AM C.585226 p [M338], C.585233 p [SK099], C.585234 p [M326], C.585236 p [M457, SK183], C.595973 p [M327]); Lazarus Island channel headland, 01°13.085’N, 103°51.429’E, SI04-4 (AM C.585985 10p).
External morphology. Foot sole, foot wall and cephalic folds evenly dark yellowish grey, paler at foot/ wall edge; foot wall and mantle more yellowish; mantle lobed with small black pigmentation at thickened edge aligning with rib interstices; translucent, as wide as foot wall, covers exposed inner shell lip; genital pore inconspicuous, located on foot wall to right anterior of right cephalic fold; two small black epithelial spots centralised on two centrally touching unpigmented cephalic folds; pneumostomal lobe relatively long, under the mantle, unpigmented, between the right ADMs.
Shell (Figs 54K–L, S; Table S9). Medium to large sized (max sl mean = 11.6 mm, SD = 1.7 mm, n = 7), ovate; medium to tall; apex offset central sightly posterior (usually eroded), apical sides strongly convex, protoconch direction heterostrophic (n = 2; Fig. 54S), shell whorl dextral; growth striae prominent in bands, shell thickness thick; rib count (mean = 45.7, SD = 5.5, n = 7), primary ribs pale white, fairly straight, increasingly raised and protrude beyond shell lip to unevenly scallop and corrugate the edge; 1–2 interspersed pale white finer secondary ribs, rib interstices darker; paired primary ribs on siphonal ridge, no more prominent than other primary ribs. Interior shell margin dark brown to tan, white rays align on shell margin under primary/secondary ribs, siphonal groove distinct, same colour as shell edge, points to right anterior; spatula dark chocolate brown to mottled tan; ADM scar distinct, CMS straight, paler than shell lip; thickening of shell lip translucent, infills and reduces lip scalloping, spatula becomes whitened.
Reproductive system (Fig. 58A; n = 1). Positioned within right side of coelom, against foot wall on foot muscle, under the respiratory cavity; epiphallic parts positioned between RAM and BM. GA very small indistinct with singular GP through foot wall; AO small broad bluntly pointed, joined to GA; ED elongated narrow thickened, slightly centrally bent, joins to GA; GA, AO, ED all white muscular fibrous tissue; EG large, soft whitish tissue, folded, joins ED; single wide flagellum (F1) lays over BM, shorter but similar width to ED, appears as an extension of ED. BD and CD connect side-by-side to GA between AO and GP, both ducts thick short bent smooth whitish, pass together through RAM (BD over thicker CD) into soft white folded tissues of MG, BC embedded in folds close to embedded blackish SV; BD short narrow bent before BC, without distal loop or MA to inner anterior foot wall; CD shorter wider than BD; BC relatively large bulbous, thin whitish translucent test (2 SPM in brownish gelatinous mass of BC); MG / AG complex relatively large; HD short narrow coiled, links ducts in soft white folded tissues of AG to yellowish granulated HG; AG / MG larger than HG, both outer sides curved to curvature of inner foot wall.
Spermatophore (Fig. 58B). Relatively short (length = 4.25 ± 0.196 mm, n = 2, flagellum incomplete), test thin, translucent, containing a white gelatinous core mass; over half-length comprises a translucent bulbous cylindrical head section (head length = 1.646 mm, SD = 0.213 mm, n = 2; mean ~ 39% of SPM length, SD = 3%); tip bluntly rounded, with a prominent twist before tapering into a filamentous transparent flagellum; head section much thicker than flagellum (head width = 116 ± 16 μm, flagellum width = 12 ± 0 μm, n = 2); both sections smooth, featureless; 7–8 SPM tightly coiled in one BC (AM C.585236).
Comparative remarks. In our mitochondrial tree (Figs 1, 4, Clade E), S. costellata sp. nov. (normalis group, unit 13) is more closely related to four species, S. normalis, S. madangensis, S. fuliginata, and S. campestra. It differs from any of these by COI distances of ≥ 7.3%. Throughout its range, this species has been found in sympatry with four congeners.Three species are sympatric in northern Australia, from N Qld to Nhulunbuy, NT: For comparisons with S. viridis, S. atra, and S. normalis refer to comparative remarks under these species. In Singapore the species is sympatric with S. viridis and S. alba; refer to comparative remarks under these species. Siphonaria madangensis sp. nov. differs in having a smaller, lower shell, a smaller AO, larger BC, and a more bulbous SPM. The specimen identified as ‘ normalis group, unit 13’ in Dayrat et al. (2014: 266, fig. 3O) is a member of S. costellata.
Distribution and habitat. Recorded from Thailand, Singapore, Malaysia and NT, Australia (Fig. 55). In this study, found in sheltered and vertical positions on moderately exposed rocky shores across upper littoral levels (Fig. 54T).
Etymology. From ‘costellata’ (Latin = ribbed), referring to the finely ribbed shell; adjective.
description: Published as part of 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), pp. 1-217 in Megataxa 13 (1) on pages 147-148, DOI: 10.11646/megataxa.13.1.1, http://zenodo.org/record/14984186