Siphonaria tanchaensis, B. W. Jenkins & Köhler, 2024

Siphonaria tanchaensis View in CoL sp. nov.

( Figs 74D–F, O–P View FIGURE 74 , 75C–D View FIGURE 75 )

Siphonaria laciniosa View in CoL — Hubendick 1946: 46; Oyama et al. 1954: 14; Kira 1962: 201, pl. 69, fig. 11a, b; Habe & Kohno 1980: 23 (not S. laciniosa ( Linnaeus, 1758)) View in CoL .

Siphonaria (Siphonaria) laciniosa View in CoL — Higo 1973: 287 (not S. laciniosa ( Linnaeus, 1758)) View in CoL .

Siphonaria ‘ laciniosa View in CoL group, unit 20’— Dayrat et al. 2014: 267, fig. 4B.

Material examined. Type material. Holotype: from Okinawa, Tancha Bay , 26°27.897’N, 127°49.131’E; coll. B.W. Jenkins, JP01-5, 20 March 2020 ( AM C.585615 [M495, SK314], Fig. 74D View FIGURE 74 ) GoogleMaps . Paratypes: same data as holotype ( AM C.585949 15p, C.584912 p [SK386], Fig. 74E View FIGURE 74 ); GoogleMaps Moon Bay (26°26.653’N, 127°48.230’E), Onna, Okinawa, Japan; coll. B.W. Jenkins, JP01-4, 18 March 2020 ( AM C.584913 p [M505, SK326], Fig. 74F View FIGURE 74 ) GoogleMaps .

Other, non-type material. Japan, Okinawa: Cape Maeda, 26°26.573’N, 127°46.113’E, JP01-2 ( AM C.585624 5p); GoogleMaps Moon Bay, Onna 26°26.653’N, 127°48.230’E, JP01-4 ( AM C.595956 5p); GoogleMaps Sun Marina Beach, Onna, 26°27.842’N, 127°48.755’E, JP01-1 ( AM C.585623 5p, C.595921 p [SK537], C.595924 p [SK538], C.595926 p [SK536]); GoogleMaps Tancha Bay 26°27.897’N, 127°49.131’E, JP01-5 ( AM C.584853 p [SK399]); GoogleMaps Tancha Bay 2, rocky point 26°27.941’N, 127°49.194’E, JP01-6 ( AM C.585628 4p) GoogleMaps .

External morphology ( Fig. 74O View FIGURE 74 ). Foot sole dark grey; foot wall, mantle, cephalic folds, pneumostome lobe evenly grey, paler to foot edge; irregular small blotches of black pigmentation on foot wall and centre of cephalic lobes; mantle translucent, wider than foot wall, covers inner shell lip, wider at anterior, mantle 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 fold; pneumostomal lobe under mantle.

Shell ( Figs 74D–F View FIGURE 74 ; Table S9): medium sized (max sl mean = 19.8 mm, SD = 2.3 mm, n = 4), circular ovate; tall; apex offset central and sightly left, apical sides convex; protoconch direction homostrophic (n = 2; holotype C.585615 [M495], paratype C.584913 [M505]), shell whorl dextral; shell exterior and edge uneven; growth striae prominent; pale brown radial banding with irregular darker flecks; shell thickness thick; rib count (mean = 43.3, SD = 0.8, n = 4), 10–12 fairly evenly spread primary ribs, pale white, weakly bent and uneven, strongly raised rounded ridges (some> 1mm), widen to shell edge, protrude beyond shell lip to unevenly scallop between primary ribs and corrugate the edge, ends of primary ribs may be flared creating uneven roughness on rib ridges; between primary ribs brown flecks/bands with 0–6 finer whitish secondary ribs (commonly 2), rib interstices narrow darker; siphonal ridge formed by three adjacent ribs, no more raised than other primary ribs. Interior shell margin white to cream, with fine dark brown markings on shell edge under rib interstices, may extend over shell margin, white rays align on shell edge under primary/ secondary ribs, ADM scar distinct, brown to white as spatula; cephalic muscle straight to weakly concave; thickening and vivid whitening of shell lip common ( Fig. 74F View FIGURE 74 ).

Reproductivesystem ( Fig.75C;n View FIGURE 75 =2). Proportionally RS very large structure to animal size, positioned within coelom under the respiratory cavity, epiphallic parts compacted, positioned over back of BM to side of RAM, F1 draped over left side of BM; very small GA, AO broad, bent, rounded, bluntly pointed, rests against MG, joins top of GA; ED long, narrow, bent, joins side of GA; EG medium with folds, overlaps join of ED flagellum (F1) join, F1 long, narrow, appears as an extension of ED; AO, GA and ED all muscular white tissue; BD and CD (bulbous at join) connect closely together in opposing directions into GA ED and AO junction; BD with distal loop and MA, BD longer and slightly narrower than CD, both ducts smooth, narrow, pass together through outer side of RAM ( BD above CD), connecting into folds of MG; BC embedded in MG, smallish, bulbous test soft translucent, SV embedded within AG; HD lobed, links AG to small brownish granulated HG, MG and AG small folded soft white tissue, anterior edge of MG lobed, sides match curvature of inner foot wall at right posterior quarter of coelom.

Spermatophore ( Fig. 75D View FIGURE 75 ). Broad head with short flagellum (length = 1.67 mm, n = 1); head section cylindrical, bulbous, centrally bent, tip rounded; test thin, smooth, featureless, translucent encasing a white opaque thin central core; short looped tapering section merges head to filamentous flagellum, head longer, wider than flagellum (head length = 1.41 mm, flagellum length = 0.26 mm, n = 1, 85% of SPM length, head width = 172 μm, flagellum width = 21 μm); 2 SPMs tightly coiled in brown gelatinous mass in BC of one specimen [SK538].

Comparative remarks. Siphonaria tanchaensis sp. nov. ( laciniosa group, unit 20) represents a well-differentiated lineage in the mitochondrial tree ( Figs 1 View FIGURE 1 , 3 View FIGURE 3 ). It differs from its sister species S. poindimiensis sp. nov. (unit 19) by COI distances of ≥ 21.8% (Table S6). We found S. tanchaensis sp. nov. in sympatry with four congeners on Okinawa: For comparative remarks see under S. camura sp. nov., S. rucuana , S. subatra , and S. sipho , respectively. Generally, shell features of this species closely resemble those of other members of the laciniosa group (i.e., few prominent, weakly extending primary ribs, secondary ribs patterning and colouration, internal colouration, irregular weakly scalloped shell edge, thickened white shell margin lip). Figured specimens of ‘ S. laciniosa ’ in Kira (1962: pl. 69, fig. 11) from central Honshu and of ‘ laciniosa group, unit 20’ ( Dayrat et al. 2014: fig. 4B) from Okinawa corresponds well with typical features of S. tanchaensis sp. nov.

Distribution and habitat. Recorded as endemic to Okinawa, Japan ( Fig. 73 View FIGURE 73 ). In this study, found on exposed rocky shores at mid littoral level ( Fig. 74P View FIGURE 74 ).

Etymology. Named after the type locality of Tancha Bay, Okinawa, Japan.