Ilanga fulgens
Creators: name: Vilvens, Claude
name: Williams, Suzanne T.
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Trochida
Solariellidae
Ilanga
Ilanga fulgens

description: Ilanga fulgens (Dall, 1907) (new comb.)
(Figs 11 A–H, 12A-N, 13A–O, 14A-D, Table 5, Key 2: 13)
DNA ref: Ilanga 4 & Ilanga 17 (Williams et al. 2013; Sumner-Rooney et al. 2016)
COI sequence data: GenBank Accession numbers: Ilanga 4: HF586291, HF586292. Ilanga 17: HF586260, HF586254, HF586255, HF586256, HF586257, HF586258, HF586259, HF586261. Ilanga fulgens (this study): MK393381.
Note that sequence published as ‘ Microgaza fulgens’ in Williams et al. 2008 is not this species (= Ilanga 19 in Williams et al. 2013).
Microgaza fulgens Dall, 1907: 168–169. Type locality: Sea of Japan, stn 4891, 10°22’.7S, 123°16’.5E, 181 fathoms (390 m). U. S. Nat. Mus. Cat. No. 110543.
Microgaza fulgens Kuroda, Habe & Oyama 1971: 42, pl. 12, figs. 15–16.
Microgaza fulgens Kaicher 1986: card TR3-4569.
Microgaza fulgens Higo, Callomon & Goto 1999: 65.
Archiminolia fulgens— Marshall, 1999: 24.
Microgaza fulgens Sasaki 2000: 77, pl. 38, fig. 114.
Microgaza fulgens Poppe, Tagaro & Dekker 2006: 129, pl. 68, fig. 3.
Archiminolia fulgens Vilvens 2009: 80–81, figs. 31–34 (part)
Microgaza konos Vilvens 2009: p.88 Figs 64–66. Type locality. Taiwan, Bashi channel, TAIWAN 2000, stn DW36, 21°55’N, 120°36’E, 305 m. Syn. nov.
Type material. USNM 110543 (Dall, 1907).
Material examined. Northeastern coast of Taiwan. TAIWAN 2001: stn CP75, 24°57’N, 122°02’E, 139 m, 1 dd. — Stn CP 76, 24°57’N, 122°02’E, 115–170 m, 1 lv (DNA sample MNHN IM-2007-18548). —TAIWAN 2002: stn CP162, 22°10’N, 120°38’E, 190–200 m, 2 dd, 1 dd juv 3.7x 7.7 mm
.
Philippines, Bohol Sea. PANGLAO 2005: stn CP2331, 9°39’N, 123°48’E, 255–268 m, 1 lv (DNA sample MNHN IM-2007-18417), 2 dd juv. — Stn CP 2332, 9°38’N, 123°44’E, 584–596 m, 2 lv (1 DNA sample MNHN IM-2007-18416), 9 lv. — Stn CP 2340, 9°29’N, 123°44’E, 271–318 m, 3 lv (DNA samples MNHN IM-2007-18418, 18419, 18420), 19 lv, 1 juv lv. — Stn CP 2343, 09°27’N, 123°49’E, 273–356 m, 5+15 lv sub, 1+6 dd juv. — Stn CP 2344, 9°28’N, 123°50’E, 128–142 m, 2 lv (1 DNA sample MNHN IM-2007-18421), 3+1 dd juv. — Stn DW 2371, 08°35’N, 123°16’E, 172–175 m, 1 dd sub, 3 dd juv. — Stn CP 2380, 8°41’N, 123°18’E, 150–163 m, 3 lv, 1lv sub, 2 lv juv. — Stn CP 2381, 8°43’N, 123°19’E, 259–280 m, 1 lv (DNA sample MNHN IM-2007-35122), 1 sub dd. — Stn CP 2383, 08°45’N, 123°19’E, 338–351 m, 1 dd sub. — Stn CP 2392, 09°29’N, 123°41’E, 242–400 m, 24 lv, 2 sub lv, 3 juv lv. — Stn CP 2393, 9°30’N, 123°42’E, 356–396 m, 1 lv (DNA sample MNHN IM-2007-35011), 1 sub dd. — Stn DW 2402, 09°31’N, 123°42’E, 101–118 m, 2 lv. — Stn CP 2406, 09°41’N, 123°47’E, 334–389 m, 2 lv.
South China Sea. ZHONGSHA 2015: stn CP4146, 16°09’N, 114°16’E, 232–314 m, 1 lv (DNA MNHN sample IM-2013-59757).
Japan. Wakayama pref., Kushimoto, 90–180 m, 1 lv (C. Vilvens coll.).
Distribution. Japan, 50–350 m (Sasaki, 2000); Taiwan, 139–350 m, Philippines, 82–584 m (computed using data of Poppe et al. 2006); Eastern Indonesia, 181–184 m (dd) (Vilvens, 2009).
Diagnosis. A medium sized Ilanga species with a moderately depressed, conical spire, a subangulate periphery, 4 spiral cords on first teleoconch whorl, weak to very weak subsutural pleats, angulate umbilicus with numerous, sometimes weak, axial pleats all around, bordered by a smooth spiral cord at rim and 6–8 thin spiral cords inside.
Description (supplementary—based on the original description and DNA samples studied). Shell of medium size for genus (H up to 7.7 mm, W to about 12.9 mm), wider than high, shape conical; shell glossy; spire moderately depressed, height 0.53x to 0.66x width, 1.4x–1.8x aperture height; slightly subangulate to almost rounded periphery; umbilicus very broad and deep. Protoconch ca. 200–270 μm wide, 1.25 whorls, rounded, with about ten weak spiral cords sometimes hard to distinguish, only median cord stronger and clearly defined; straight terminal lip, without obvious expansion. Teleoconch up to 4.8 slightly convex whorls, without shoulder, with spiral cords and thin axial threads on first whorls disappearing on next whorls. Suture weakly canaliculated on first whorls. First teleoconch whorl convex, sculptured by 4 thin, evenly spaced, spiral cords appearing immediately; P1 weaker, possibly already disappearing at end of whorl; P2 at edge of angulate subsutural ramp; weak, thin prosocline threads. On second teleoconch whorl, spiral cords disappearing after half whorl, P2 disappearing last; subsutural ramp still present, without spiral cord on rim. On third whorl, axial threads entirely traversing whorl; interspace approximately as wide as thread; subsutural ramp ceasing near end of whorl; no subsutural pleats or possible weak subsutural pleats; narrow translucent (next whorl visible) subsutural spiral band. On last whorls, axial threads very weak but still present; nodules ceasing; few thin abapical spiral grooves around subangular periphery. Aperture broadly triangular; peristome incomplete; outer and inner lip thin, without thickening or weak basal thickening against umbilical rim. Base convex, nearly smooth or with very weak (sometimes hard to see) axial grooves on inner third, reaching umbilical rim. Umbilicus broad (diameter about 30–38% of shell width), central, funnel-shaped, with perspective to apex, with moderately angulate rim marked by a rather weak, thinsmooth spiral cord; moderately convex to almost vertical wall with 6–8 smooth spiral cords and without axial threads inside, spiral cords possibly stronger in adapical part.
Colour: Teleoconch nacreous white or nacreous pink to light brown or orange brown, with variable pattern of brownish regular flames (sometimes in 1 or 2 narrow bands of chevrons), patches or dots; base with regular maculation; protoconch off-white.
Operculum: Corneous, multispiral with central nucleus, light brown.
Remarks. Here, we formally synonymise I. fulgens and Microgaza konos Vilvens, 2009. The type locality of I. fulgens is Japan, but more recently the name has been applied to samples from the Philippines (Poppe et al. 2006), whereas I. konos was described for specimens from Taiwan. We synonymise these species based on low levels of genetic divergence and only minor differences in shell morphology. In particular, it appears that the original description of I. konos was based on a subadult sample: compared to the new samples, the holotype of I. konos is smaller with only 4 whorls, a slightly more elevated shape and less numerous axial pleats around the umbilicus, while the other conchological features are similar to those observed in I. fulgens. Umbilical characters were previously the main characters used to distinguish between I. konos and I. fulgens, but with a larger sample size these characters show an overlapping range of sculpture and shapes.
Poppe et al. (2006) also listed Solariella zacalloides Schepman, 1908 (Fig. 11I) as a synonym of I. fulgens, but without explanation. We are unable to comment on this opinion because the type material of this species was not studied here.
Molecular data show that specimens from the Philippines identified as I. fulgens cluster together (Ilanga 17 in Williams et al. 2013), separately to those collected from Japan and Taiwan (Ilanga 4 in Williams et al. 2013). A single specimen from the South China Sea (new sequence, this study) is distinct from these two groups. Despite small morphological differences among specimens from the different collecting localities (as it can be seen on Figs 11–14), we conservatively consider both genetic differences and morphological variation to represent intraspecific variation.
description: Published as part of Vilvens, Claude & Williams, Suzanne T., 2020, New species of Ilanga (Gastropoda: Trochoidea: Solariellidae) from the Indo-West Pacific, pp. 201-257 in Zootaxa 4732 (2) on pages 222-227, DOI: 10.11646/zootaxa.4732.2.1, http://zenodo.org/record/3663329