Eosaster nadiae

Mah, Christopher L., 2017, Overview of the Ferdina - like Goniasteridae (Echinodermata: Asteroidea) including a new subfamily, three new genera and fourteen new species, Zootaxa 4271 (1), pp. 1-72 : 14-16

Eosaster nadiae nov. gen, nov. sp.

Figure 3 A–F

Etymology. The species is named in honor of Dr. Nadia Améziane, previous curator of Echinodermata at the Muséum national d’Histoire naturelle and now Head of the Marine Invertebrates section.

Diagnosis. Body is stellate to weakly stellate. Body flat. Abactinal surface covered by weak to strongly convex abactinal plates. Body, abactinal, marginal, actinal surfaces, completely covered by a continuous layer of fine granular tegument with no bare regions. Eight to 20 marginal plates per interradius (arm tip to arm tip) in medium to larger sized individuals (R> 1.5 cm). Marginals quadrate in outline but strongly convex in profile. Actinal region composed of approximately three series in chevron formation. Furrow spines in single row, two or three spines per adambulacral plate. Subambulacral accessories absent. Granules cover surface of adambulacral plate. No pedicellariae observed.

Taxonomic comments. The distinctive large, hemispherical abactinal plates on this species in combination with the marginal plate morphology and the granular tegument distinguish this species from any other known goniasterid species.

Eosaster nadia e n. gen., n. sp. shares the large, hemispherical abactinal plates and the granulated surface tegument with the genus Ferdina . However, unlike known adult Ferdina , e.g. F. flavescens , E. nadiae possesses a more planar body form with a homogenous marginal plate series which frames the abactinal plate surface, similar to what is observed in most Goniasteridae . Eosaster n. gen. however appears dissimilar to juvenile Ferdina mena (as described below) but shows a broader body form with short arms more similar to Bathyferdina .

Occurrence. New Caledonia, 215–600 m.

Description. Body thick, variably stellate in shape (R/r=1.8–2.4), arms triangular, interbrachial arcs rounded ( Fig. 3 A). Abactinal surface weakly arched.

Abactinal plates strongly convex forming very rugose surface on disk ( Figs 3 A, B). Individual plates vary in shape from circular and oval to quadrate and polygonal. Plates larger proximally, becoming smaller closer to contact with superomarginal series. Abundance of plates decreasing distally where superomarginals abut over midline (i.e. in contact distally). More angular plates interradially, more rounded plates along radii. Paired plates in each interradius. Smaller plates distally, adjacent to superomarginal border. Abactinal surface completely covered by continuous layer of densely packed granulation. Granules larger, more coarse centrally on top surface of each abactinal plate. Granular tegument dense, covering boundaries between plates ( Fig. 3 B, C). Abactinal plates cream to light brown becoming very dark brown between plates ( Fig. 3 B). Madreporite quadrate to polygonal, flanked by 4 disk plates. Papulae single, four to eight around each abactinal plate ( Fig. 3 C). Papulae absent interradially, present primarily along radial regions on arms. Pedicellariae not observed.

Marginal plates 8–20 per interradius from arm tip to arm tip ( Fig. 3 A), strongly convex in transverse crosssection. Quadrate to circular in outline. Marginal plate series matched 1:1, equivalent numbers of plates in superomarginal and inferomarginal series. Penultimate superomarginals compact, more quadrate in shape. All marginal plates covered by granular tegument containing densely packed, fine granulation identical to that covering abactinal, actinal surface ( Figs 3 A, C, D, E, F). Smaller individuals (R=~5.0 mm to 1.0 mm) display variably sized quadrate bald patches on superomarginal and inferomarginal surfaces. Distalmost 2–3 pairs of superomarginals abutted over midline ( Fig. 3 C). Distalmost inferomarginals 2–3 pairs from the terminal with blunt, conical nubbin like prominence at center of each plate. Inferomarginal series forms ledge, jutting out from below superomarginal series. Terminal plate triangular, bare, spine conical, blunt present. Peripheral accessory structures absent.

Actinal surface composed of 2–3 series of chevrons ( Figs 3 E, F). Actinal plates quadrate to polygonal with rounded edges with tumid surface. Most ordered, quadrate adjacent to adambulacrals becoming more irregularly shaped and ordered adjacent to inferomarginal series. Actinal intermediate plates 2x–4x the size of adambulacral plates. Actinal plates continue along arm to approximately half way on length. Surface completely covered by continuous layer of granulation, identical to that covering abactinal, marginal plate surface. Continuous granular layer extends over adambulacral plates to base of furrow spines ( Fig. 3 E). Granules larger adjacent to furrow spines. Pedicellariae absent from actinal surface. Actinal region very light colored relative to darkened regions on abactinal surface.

Furrow spines 2–3 per plate. Each spine thick, polygonal to trigonal in cross-section, wide, and appearing in continuous series. Discrete breaks between adambulacral plates obscured by granulation. Subambulacral spines and all other adambulacral ornamentation absent. Pedicellariae absent from adambulacral plates. Oral plates covered by granular tegument with no accessory structures (i.e., no spinelets, etc.), which becomes slightly more dense adjacent to furrow spines. Furrow spines on oral plates consistent in number, shape with those on furrow spines.

Coloration on dried specimens shows mottled, contrast coloration. Color in life is orange. One four-armed specimen (MNHN-IE-2013-6823) observed.

Material examined. Holotype: MNHN - IE- 2013-6810 ; South New Caledonia, 23°21’S 168°5’E, 215–260 m; Coll . SMIB 4 no station, N/ O Alis. 9 March 1989; 1 dry spec. R= 3.1 cm, r=1.3. Paratypes: MNHN-IE-2013-6818; Off Noumea , New Caledonia 23˚ 40.9 S,168˚ 0.8 E , 250–270 m; Coll. N / O. Alis, SMIB 5 ; 1 dry spec., R=1.0, r=0.5. MNHN-IE-2013-6819; Off Noumea, New Caledonia 23˚21.8’S, 168˚4.7’E , 225–270 m; Coll. N/O Alis, SMIB 5; 2 dry specs. R=1.5, r=0.9; R=1.3, r=0.7. MNHN-IE-2013-6820; Off Noumea, New Caledonia, 23˚39.7’S, 167˚59.7’E. 280 m; Coll. N.O Vauban, SMIB 3 , St. DW 20; 2 dry specs. R=1.5, r=0.7; R=1.3, r=0.8 . MNHN IE- 2013-6824 ; Noumea , New Caledonia, 23˚ 40.6 S,168˚ 1.1 E, 260–270 m ; Coll. N/O Alis, SMIB 5; 2 dry specs. R=1.7, r=1.0, R=0.9, r=0.5. MNHN-IE-2013-6816; South New Caledonia 23˚21’S, 168˚05’E. 215–260.0 m.; Coll. N / O Alis, SMIB 4 , st. DW 55; 1 wet spec. R=1.6, r=0.9. MNHN-IE-2013-6817; Off Noumea , New Caledonia, 23°40.8 S 168°1.1’E, 230–270 m; Coll. N.O Alis, SMIB 5 , st. DW 77; 1 dry spec. R=1.8, r=1.0. MNHN-IE-2013- 6814 ; Southern New Caledonia, 23˚41’S 168˚01’E, 245–260.0 m; Coll. N.O Alis, SMIB 4 , St. DW 51; 3 dry specs. R=1.6, r=0.8; R=1.9, r=1.0; R=1.9, r=1.3. MNHN-IE-2013-6812 ; New Caledonia, 23˚53’S, 167˚11’E, 375–402 m; Coll. N.O Vauban, dr. 15; 1 dry spec. R=1.1, r=0.7. MNHN-IE-2013-6821; Off Noumea, New Caledonia, 23˚ 41.5 S,167˚ 59.4 E , 338 m; Coll. N / O Vauban, SMIB 3 ; 1 dry spec. R=0.85, r=0.4. MNHN-IE-2013-6813; New Caledonia, 24.°39.84' S 168.°38.50' E , 582–600 m; Coll. NORFOLK 2; 1 dry spec., R=2.2, r=1.2. MNHN-IE- 2013-6823 ; Southern New Caledonia, 23˚41’S, 168˚01’E, 245–260 m; Coll. N / O Alis, SMIB 4 DW 51;1 dry spec. (4 arms), R=1.1, r=0.5. MNHN-IE-2013-6825 ; Southern New Caledonia, 23˚41’S 168˚01’E, 270 m; Coll. B. Richer de Forges, SMIB 5 , St.DW 70; 1 dry spec. R=1.5, r=0.8. MNHN-IE-2013-6826; Off Noumea , New Caledonia 23˚40.2’S, 168˚0.9’E. 235–245.0 m; Coll. N.O Alis, SMIB 5 , St.DW 74; 1 dry spec., R=1.9, r=1.1. MNHN-IE-2013-6811; Off Noumea , New Caledonia, 23˚ 41.3 S,168˚ 01.1 E, 260–285 m; Coll. N / O Alis, SMIB 5 , DW 79. 2 dry specs. R=1.6, r=0.8; R=0.9, r=0.4. MNHN-IE-2013-6815 ; New Caledonia, 1 dry spec. R=0.8, r=0.4. MNHN-IE-2013-6832; Banc Antigonia, Norfolk Ridge, New Caledonia, 23˚22 S, 168˚03 E, 257–269 m ; Coll. Lozouet, Boisselier, Richer de Forges, N / O Alis NORFOLK 1; 2 wet specs. R=3.1, r=1.3, R=1.2, r=1.0. MNHN- IE- 2013-6833 ; Norfolk Ridge, New Caledonia, 23°22’S, 168°02’E , 204–216 m; Coll. Lozouet, Boisselier, Richer de Forges, 26 June 2001; 3 wet specs R=2.0, r=0.7; R=1.8, r=0.8; R=1.8, r=0.7. MNHN-IE-2013-6696; Banc Jumeau-ouest, Norfolk Ridge, New Caledonia. 237–250 m, 23°40’S, 168°01’E; Coll. Lozouet, Boisselier, Richer de Forges , NORFOLK 1, DW 1667, 21 June 2001; 4 wet specs. R=2.3, r=1.4; R=1.8, r=1.1:R=1.6, r=0.7, R=1.6, r=0.9. MNHN-IE-2013-6697; Banc Antigonia , Norfolk Ridge, New Caledonia, 204–216 m, 23°22’S, 168°02’E , 204–216 m; Coll. Lozouet et al., IRD, NORFOLK 1 CP 1713; 3 wet specs. R=1.9, r=0.8; R=1.7, r=0.8; R=1.9, r=0.9; MNHN-IE-2013-6827 ; South New Caledonia. 240–300 m. Coll. B. Richer de Forges, ORSTOM BERYX 11 . 1 dry spec. R=1.8, r=1.0; MNHN-IE-2013-6828 ; New Caledonia, 24°46’S 168°9’E , 232 m; Coll. Richer de Forges, CHALCAL II, DW 70; 1 dry spec. R=1.5, r=0.8. MNHN-IE-2013-6694; Jumeau O seamount, Norfolk Ridge, New Caledonia, 23°39’S –23°43’S to 168°00’E–168°01’, 235–400 m; Coll. AZTEQUE, Ch. 04; 1 wet spec. R=1.8, r=1.0; MNHN-IE-2013-6695; New Caledonia, Coll. NORFOLK 1, CP 1216; 1 wet spec. R=2.3, r=1.0; MNHN-IE-2013-17081 ; New Caledonia 23°39.74’S to 167°59–46’E, 315–325 m; Coll. N / O Alis ORSTOM, BATHUS 3 , CP 803; 1 dry spec. R=2.3 r=1.3.

Figures

FIGURE 3. Eosaster nadiae n. gen., n. sp., Holotype, MNHN-IE- 2013 - 6810. Scale bar = 2.0 mm. A. Abactinal surface. Scale bar = 3.0 mm. B. Abactinal surface showing plate detail. C. Abactinal-lateral view showing superomarginal and inferomarginal plate details. D. Abactinal and superomarginal detail. E. Inferomarginal-actinal plate surface detail. F. Oral surface.