Siphonaria striata, Jenkins, Bruce & Köhler, Frank, 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 : 180-182

publication ID	https://doi.org/10.11646/megataxa.13.1.1
DOI	https://doi.org/10.5281/zenodo.14989371
persistent identifier	https://treatment.plazi.org/id/0D49832F-FF2E-82A9-FCCA-FF02FDABFC56
treatment provided by	Plazi
scientific name	Siphonaria striata
status	sp. nov.

Treatment

Siphonaria striata View in CoL sp. nov.

( Figs 71J–L, T View FIGURE 71 , 72G–H View FIGURE 72 )

Material examined. Type material. Holotype, from Reef in front Sud-Sud Hotel , Itampolo, 24°41.431’S, 43°56.603’E, Madagascar; coll. O. Griffiths, MA03-1, July 2018 ( AM C.584952 [M264], Fig. 71J View FIGURE 71 ) GoogleMaps . Paratypes same data as holotype ( AM C.585376 10+p, C.584953 p [M265 protoconch H10], Fig. 71K View FIGURE 71 , C.584954 p [M266], Fig. 71L View FIGURE 71 , C.584832 p [SK402]) GoogleMaps .

Other, non-type material. Madagascar: Ilot de Lokaro , 24°56.5’S, 47°07.1’E, TM05 ( MNHN IM-2009- 13792 p [M579], IM-2009-13769 p [M581]) GoogleMaps .

External morphology. Foot wall, mantle, cephalic folds and pneumostome evenly cream, foot sole darker, paler to foot edge; mantle translucent, wide, thin, mantle edge weakly lobed with thickened whitish band; no dark/ black pigmentation markings.

Shell ( Figs 71J–L, T View FIGURE 71 ; Table S9). Small sized (max sl mean = 15.6 mm, SD = 1.2 mm, n = 3), circular ovate; medium to tall, apex offset weakly to left and posterior of centre, apical sides strongly convex, posterior side straight to weakly convex; protoconch direction weakly homostrophic (n = 2, Figs 71K View FIGURE 71 ), shell whorl dextral; growth lines distinct; ribs (count mean = 45, SD = 2.5, n = 3), raised, whitish, straight, rib ridges rounded, width strongly increases to shell lip; rib interstices narrow, dark brown; majority of ribs primary, extend from apex to slightly protrude beyond shell edge, secondary ribs fill between primary ribs, 3 primary ribs form siphonal ridge; shell lip uneven, scalloped, aligning with primary rib ends. Interior; white rays aligning under primary ribs extend from shell lip to inner shell margin to golden tan spatula, with dark chocolate brown infill between rays; muscle scar impression distinct, same as shell margin colouring, CMS straight; thickening or whitening of shell edge not observed.

Reproductive system ( Fig. 72G; n View FIGURE 72 = 1). Positioned withincoelomundertherespiratorycavity,hermaphroditic glands positioned to posterior against right foot wall and over foot sole, epiphallic parts embedded between RAM and BM close to MG, AG and BC. Join of AO and ED distinct together at top of GA, AO smaller than GA, elongated, blunt, centrally bent; ED thick, elongated, narrower than AO; AO, GA and ED all muscular white tissue; EG broad, soft white tissue, single looped narrow flagellum F1 extends from ED; BD and CD connect side by side into GA, BD bulbous entry with short distal loop and MA in front of ED; CD enters inner side of GA; BD much longer with similar thickness to CD, both ducts smooth and pass together just inside outer side of RAM connecting into MG ( BD over CD), BC white opaque test, relatively small, bulbous, embedded along with part of BD in folds of MG / AG; HD short narrow, coiled, links broad AG to an elongated wide yellowish granulated HG, AG and MG folded, soft white tissue, AG larger than HG, with outer sides curved reflecting the close positioning to curvature of inner foot wall at right posterior quarter of coelom; SV embedded on left side of AG close to BC.

Spermatophore ( Fig. 72H View FIGURE 72 ). Body cylindrical, thread-like (length = 8.72 mm, n = 1, AL = 10.2 mm), test thin, translucent, smooth, featureless; head broad, containing a white core, laterally banded in front half, tip tapered bluntly rounded, tapers to a thin flagellum (head width = 121 μm, flagellum width = 17 μm, n = 1); single SPM tightly coiled in orange gelatinous mass in BC of the holotype.

Comparative remarks. In our mitochondrial phylogeny ( Figs 1 View FIGURE 1 , 2 View FIGURE 2 ), S. striata sp. nov. ( atra group, unit 74) forms a clade with S. alternata (unit 29) from the Caribbean and Gulf of Mexico and S. kurracheensis (unit 28) from Pakistan. It differs from S. kurracheensis by COI distances of ≥ 8.6% and from S. alternata by ≥ 5.8% (Table S5). Notably, the genetically most similar species, S. alternata , is not known to occur in the Indian Ocean. Siphonaria kurracheensis differs in having a lower, paler shell with more prominent darker and broader interior rays extending to the spatula, a shorter F1, shorter twisted ED, and BD without a bursal loop. We found S. striata sp. nov. in sympatry with two congeners in Madagascar: For comparisons with S. madagascariensis and S. itampoloensis sp. nov. refer to comparative remarks under these species. The epiphallic parts of RS are very similar to those in S. madagascariensis . However, the hermaphroditic parts differ markedly (i.e., arrangement of HG and AG, BC and BD smaller, SPM shorter in S. striata sp. nov.).

Distribution and habitat. Recorded as endemic to Madagascar, Indian Ocean ( Fig. 73 View FIGURE 73 ). In this study, found on moderately exposed inner lagoon rocky reef, at upper and mid littoral levels.

Etymology. Derived from Latin adjective “striatus” meaning ‘striated / wrinkled / lined / grooved’ referring to the shell’s external striated sculpture.