Sibogaster nieseni Mah 2016
Creators: name: Mah, Christopher L.
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Echinodermata
Asteroidea
Valvatida
Goniasteridae
Sibogaster
Sibogaster nieseni

description: Sibogaster nieseni Mah 2016
FIGURES 18A–F, 19B–F
Sibogaster nieseni Mah 2016: 136, Figs 11A–E, 12A–E, 13A–E.
Diagnosis (Modified from original description)
Body stellate (R/r=1.88 to 3.0), arms elongate, triangular in shape. Interradial arcs curved to linear. Abactinal plates round to polygonal, homogenous, flat and smooth with no surficial accessories (no granules, etc.). Each plate periphery surrounded by discrete ring of granules, 20–25, each oval to quadrate in outline, granules large occupying 25–30% of the total diameter of granule+plate. Glassy tubercles absent. Papulae 3–6 per plate present at plate angles. Marginal plates 24–36 per interradius. Surface of each plate flattened, smooth, flat devoid of surficial accessories. Inferomarginal plates bare on lateral surface adjacent to superomarginals, but actinal surface covered by granules. Actinal intermediate regions covered by granules, 8–30, hemispherical to pointed. Pedicellariae variably present or absent on abactinal, marginal and actinal plate surfaces. Pedicellariae small (~ 0.25 cm), tong-like with blunt, paddle-like blades, inset into a shallow pit. Furrow spines 6–10, mostly 7 to 8, quadrate in cross-section with blunt tips. Subambulacral spines 3–5, round to polygonal in cross-section with variable morphology in Atlantic versus Pacific individuals. Adambulacral pedicellariae one or two, elongate, tong-like in shape, thick with complementing valves, taller than furrow spines. Pedicellariae elongate valves, variably present on adambulacral plates sitting adjacent to subambulacral spines, occurring irregularly from the third adambulacral and distally along the furrow series. Oral plates with 8–10 furrow spines.
Galapagos variation
A specimen from the Galapagos Islands showed variation largely tied to the adambulacral spination and pedicellariae. This specimen was R =5.3 and smaller than most individuals used for the type series. Actinal pedicellariae were tong-like in shape with 1 to 5 small pedicellariae present per interradius, comparable tin size to the adjacent actinal granules. Furrow spines were fewer, 3 to 7, blunt tipped, quadrate in cross-section with subambulacral spines 4 to 6, single elongate.Adambulacral plates with tong-like pedicellariae on each plate, valves rectangular. Adambulacral plates displayed many more pedicellariae than on the type specimens.
Variation in North Pacific (Japanese) specimens
NSMT E13675 displays numerous small, narrow paddle-shaped pedicellariae on superomarginal and inferomarginal plate surfaces. Furrow spines 9 to 10 in straight series, quadrate in cross-section with notched tips.
Comments
Sibogaster nieseni was described from material collected in the tropical Atlantic and the North Pacific, below 2000 m depth. Subsequent collections add to knowledge of this species’ presence at comparable depths throughout the Pacific and especially the Indian Ocean and indicating that it is widely occurring throughout bathyal and deeper settings (1000 to 5000 m).
The widespread distribution of this species invites questions regarding the extent of variation in morphology as well as ecology. Although variation was observed, the overall appearance of Sibogaster nieseni was found to be surprisingly consistent. Abactinal, marginal and actinal surfaces as well as overall body shape (R /r=1.8 to 3.0), arm and disk shape were similar, especially at relatively large (R>2.0 cm) sizes. Only one goniasterid species, Hippasteria phrygiana (Parelius, 1768) is known to show a comparably widespread distribution with individuals recorded from the Atlantic, Pacific, and Indian Ocean (Foltz et al. 2013; Mah et al. 2014). Morphology in H. phrygiana was highly variable, so much so that multiple species were recognized across its range. However, Sibogaster nieseni and Hippasteria phrygiana occur at different bathymetric settings, 640 to 4175 m versus 10 to 1221 m respectively, dictating different environmental influences on their respective morphologies. Sibogaster nieseni’s overall life mode and observed presence on soft bottoms might suggest more similarity with other widely-occurring deep-sea asteroid species, such as Porcellanaster caeruleus which is cosmopolitan between 1158 to 6035 m (most collected between 1600 to 3000 m) (Madsen 1961).
Distribution
North Pacific. Taney Seamounts B and C, “NESCA” Clam sites (North Pacific), Patton Seamount and Patton Escarpment, Cascadia Plain, west of Cortez Bank, Hawaiian Islands and Johnston Atoll regions, Musicians Seamount, Japan (2597–3450 m), Celebes Sea, Indonesia, 2100–4175.
East Pacific. Galapagos, 3012 m.
Australian Occurrence (mostly Indian Ocean). Western Australia, Ningaloo, Gascoyne Marine Preserve, Balthazar Seamount off Christmas Island, off Fraser Island, Queensland. 2106–3747
Tropical Atlantic. off coast of Mauritania, 2114–3162 m.
Material Examined
East Pacific. MCZ AST-3722 Galapagos, Ecuador, 5 mi N of Albemarle Island, 3012 m, Coll. Arcturus Oceanographic Expedition, 14 April 1925, 1 dry spec. R=5.3 r= 2.1 cm.
North-Pacific-Japan. NMST E-13680. East off Mukojima, 2597–2610 m. Coll. June 7, 1997. KT-97-07, St. MKO 9, 1 wet spec. R=3.8, r= 1.3 cm.
NMST E-13679. Nankai Trough, Southeast off Asizuri-misaki Cape, Kochi Prefecture, Japan, 32º9.3’N 134º3.4’E to 32º8.9’ 134º 6.0’ E, 2739–3278 m. Coll. Tansei Maru, KT-00-8, st. 9 BT. 1 wet spec. R=3.2, r= 1.3 cm.
NMST E-13675. South off Iriomote-Jima Island, Okinawa Prefecture Japan, 23º41.3’ N 123º45.2’E to 23º42.3’N, 123º45.8E, 3436–3452 m, Coll. Hakuho-Maru, KH-73-2, st. 24, 5 March, 1973. Beam trawl. 1 wet spec. R=6.6, r= 3.2 cm.
MNHN-no number. Tropical Atlantic. North Atlantic, off the coast of Mauritania. 18°14’38.4”N 20°33’39.6”W, 3162 m. Coll. Miriam Sibuet, IFREMER, Campagne EUMELI 2, CP 8. 1 dry spec. R=2.5 r= 1.1 cm.
description: Published as part of Mah, Christopher L., 2024, New genera and species of deep-sea Goniasteridae (Asteroidea) from the North Pacific, pp. 451-500 in Zootaxa 5543 (4) on pages 484-492, DOI: 10.11646/zootaxa.5543.4.1, http://zenodo.org/record/14386776