Gigantopelta chessoia, Chen & Linse & Roterman & Copley & Rogers, 2015
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publication ID |
https://doi.org/ 10.1111/zoj.12279 |
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DOI |
https://doi.org/10.5281/zenodo.10543351 |
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persistent identifier |
https://treatment.plazi.org/id/0F16272F-FFD4-FFEB-2C15-927CFBDEF9FE |
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treatment provided by |
Felipe |
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scientific name |
Gigantopelta chessoia |
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sp. nov. |
GIGANTOPELTA CHESSOIA View in CoL SP. NOV. ( FIGS 2–7 View Figure 2 View Figure 3 View Figure 4 View Figure 5 View Figure 6 View Figure 7 )
‘Peltospiroidea n. sp. ’ – Rogers et al., 2012: 7, fig. 3d. ‘Undescribed species of peltospiroid gastropod’ – Marsh et al., 2012: 6, fig. 5c, j.
Type material
Holotype. Shell diameter 36.30 mm, 99% ethanol, Figure 3A–C. E View Figure 3 2 View Figure 2 segment, East Scotia Ridge, 56°05.31′S, 30°19.10′W (‘Cindy’s Castle’), 2606 m deep, RRS James Cook expedition JC42, ROV Isis Dive 130, 20.i.2010, leg. A. D. Rogers ( NHMUK 20150066 View Materials ) GoogleMaps . Paratypes. One dissected specimen, 99% ethanol (shell diameter 31.12 mm, Fig. 4A, B View Figure 4 ; NHMUK 20150067 View Materials ) ; growth series of five specimens, 99% ethanol ( NHMUK 20150068 View Materials ) . The above two lots have same collection data as the holotype. Growth series of five specimens, 99% ethanol ( OUMNH. ZC.2013.02.002); two specimens, 99% ethanol ( CAMZM 2015.2.1 -2); growth series of five specimens, 99% ethanol ( SMNH Type Collection 8450); five specimens, 10% buffered formalin ( NHMUK 20150069 View Materials ) GoogleMaps . Collection data for the latter three lots: E2 segment, East Scotia Ridge, 56°05.34′S, 30°19.07′W (‘ Cindy’s Castle’), depth 2644 m, RRS James Cook expedition JC42, ROV Isis Dive 134, 24.i.2010, leg. A. D. Rogers. GoogleMaps
Other material examined
Approximately 200 specimens collected on RRS James Cook expedition JC42 with ROV Isis , on dives 130, 134, and 141. Collection data for dive 130: same as holotype; dive 134: same as listed for paratype series; dive 141: E9 segment, East Scotia Ridge, 60°02.81′S, 29°58.71′W (‘Marsh Tower’), depth 2394 m, RRS James Cook expedition JC42, ROV Isis Dive 141, 30.i.2010, leg. A. D. Rogers.
Etymology
The species is named after the ChEsSo (Chemosynthetically-driven ecosystems south of the Polar Front: biogeography and ecology) Consortium (Natural Environment Research Council ( NERC) Grant NE/DO 1249X/1), which led to the discovery of ESR hydrothermal vents and this species.
Zoobank registration urn:lsid:zoobank.org:act:D46EB848-506D-45B7-8D05-35535592BD1E
Description/Diagnosis
Shell: Shell ( Fig. 4A, B View Figure 4 ) globose, three to four whorls, coiled tightly with a deep suture. Spire depressed. Aperture roughly circular, very large. Ratio of shell diameter to aperture length approximately 1:0.633 (average of 100 specimens). Shell trochiform to neritiform, holostomous. Protoconch ( Fig. 5A View Figure 5 ) consists of 0.5 whorls, diameter about 210 μm. Irregular reticulate ornament present initially, becoming obsolete distally. Suture around protoconch very deep. Teleoconch smooth, no distinct sculpture. Subtle growth lines, irregular protuberances present. Growth lines stronger on the body whorl, especially near the aperture. Periostracum thick, dark olive, enveloping the aperture. Ostracum and hypostracum milky white. Thin, fragile without periostracum. Columellar folds lacking. Callus extends to slightly cover columellar. Area around callous concave. Maximum shell diameter 45.7 mm.
Operculum: Operculum ( Fig. 3C View Figure 3 ) with central nucleus, multispiral, thin, flaky on fringe. Operculum fringe often damaged. Juveniles operculum thin, semitransparent, fringe not flaky ( Fig. 5C View Figure 5 ).
Radula: Radula ( Fig. 6A View Figure 6 ) rhipidoglossate. Ribbon approximately 0.5 mm wide and 4 mm long in adults. Formula ∼50 + 4 + 1 + 4 + ∼50. Central, lateral teeth cusp-like, pointed ( Fig. 6C View Figure 6 ). Marginal teeth long, slender, bearing ∼20 denticles at distal end ( Fig. 6E View Figure 6 ). Central tooth triangular, very broad at base, tapering dis- tally, smooth, no sculpture. Lateral teeth solid, bearing a clear protrusion at base.
Soft parts ( Fig. 7A View Figure 7 ): Foot muscular, large. Fully retractable into shell, red when alive. Small epipodial tentacles present, surrounding posterior two-thirds of operculum. Cephalic tentacles thick, triangular, broad at base and thinning towards tips. Eyes lacking. Snout tapering, thick. Oesophageal gland huge, approximately same size as aperture. Ctenidium bipectinate. Sexes separate. Shell muscle large, horse-shoe shaped. Intestine forms a simple loop.
Distribution
Only known from hydrothermal vents on segment E2 (56°05.2′S to 56°05.4S, 30°19.00′W to 30°19.35′W) and E9 (60°02.50′S to 60°03.00′S, 29°58.60′W to 29°59.00′W) of ESR. This species forms dense aggregations rather close to vent effluents.
Remarks
The dispersal mechanism is inferred to be nonplanktotrophic from the protoconch, presumably with a planktonic dispersal stage. Table 2 shows the shell parameters of G. chessoia . The relationships between the six shell parameters measured were investigated and they were all linear across all life stages. Figure 8 View Figure 8 shows a scatter plot of shell diameter against shell height. See Rogers et al. (2012) for details on location of hydrothermal vent sites.
Comparative remarks
Similar to Gigantopelta aegis sp. nov. described below. Gigantopelta chessoia can be distinguished as it has a taller spire, less extensive callus, and area around callus is concave and not flattened as in G. aegis . Differences are seen in the structure of the radula. The central tooth of G. chessoia is much wider at the base and triangular compared with that of G. aegis , which is rectangular. Lateral teeth are sculptured in both species, but the marks occur nearer to the base of the teeth in G. aegis . Gigantopelta chessoia can also be easily distinguished by the lack of sulphide deposits on the shell and operculum, at least from G. aegis found in Longqi Field, the only known habitat to date. Similarly, the operculum in G. aegis is much thicker than G. chessoia at all life stages.
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.
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