Calliaster sarahae, Mah, 2018

Mah, Christopher L., 2018, New genera, species and occurrence records of Goniasteridae (Asteroidea; Echinodermata) from the Indian Ocean, Zootaxa 4539 (1), pp. 1-116 : 22-26

Calliaster sarahae n. sp.

Figure 7 A–E

Etymology. This species is named for Dr. Sarah Samadi, professor of marine biology at the Muséum national d'Histoire naturelle, who has been instrumental in the collection of the species included herein.

Diagnosis. Body strongly stellate (R/r=3.4–4.5), arms elongate, tapering, triangular in shape. Abactinal surface plates smooth, bare with large conical spines on basal carinal plates, but absent elsewhere. Overall spines relatively few. Superomarginal plates each with one or two sharp, conical spines ( Figs 7B, C ), abutted over midline distally with abactinal plates extending along arms over 75% of distance ( Fig. 7A ). Actinal surface lacking spines, plate surface covered by granules, large pedicellariae the size of the width of each plate ( Fig. 7E ). Furrow spines mostly eight, proximally but up to 12 distally.

Comments. This species invites comparison with Calliaster thompsonae Clark and McKnight 2001 , which occurs in the Indian Ocean and in the New Zealand region with which it shares a similar overall body shape with elongate, tapering arms and a distinctly visible peripheral series of strongly convex, superomarginal plates which abut over the radius along the arm. However Calliaster sarahae n. sp. differs in that it possesses eight or more furrow spines, versus the six or seven in Calliaster thompsonae , there are far fewer conical spines on the abactinal surface limited to basal carinal arm plates and the actinal plates in Calliaster sarahae n. sp. possess are spineless, and are either bare or possess pedicellariae, whereas Calliaster thompsonae displays spines on all actinal plates.

This species is also similar to Calliaster chaos n. sp. from the Mascarene Islands, but differs in that it consistently shows fewer spines present on the abactinal surface relative to C. chaos n. sp., which displays an abundance of prominent spines on the disk. Calliaster sarahae n. sp. is also much more strongly stellate (R/r=3.4– 4.5) versus C. chaos n. sp. which shows broader arms with R/r=2.79–3.02 at a comparable size (R=~9.0 cm). Abactinal plate size and shape on C. chaos n. sp. are also heterogeneous on the arms and disk relative to the homogeneous abactinal plates on Calliaster sarahae n. sp.

Occurrence. Madagascar, Walters Shoal 285–635 m.

Description. Body strongly stellate (R/r=3.4–4.5). Arms strongly tapering, elongate ( Fig. 7A ). Interradial arcs curved. Arms upturned.

Abactinal plate round to oval shaped with flat, smooth surface ( Figs 7A, B ). Oval shaped plates most abundant along carinal and adradial series along arms with more oval shaped plates on primary circlet and proximally on disk. Smaller, more irregular shaped plates present interradially adjacent to contact with superomarginal plates. Most plate surfaces smooth, bare. Abactinal plates continue along arms between abutted superomarginals, narrowing to a single, irregular series between superomarginals. Single, large, conical sharp spines, about 1.0 cm above the abactinal surface, with swollen base present only on proximal-most carinal series on disk extending for consistently four plates in the Madagascar specimens plates along mid-radius with a prominent conical pointed spine present on the central plate of the primary circlet. These large prominent spines absent from all other abactinal plates, but other smaller, conical spines, about the width of each abactinal plate (approximately 1.0–2.0 mm) present between central and carinal plates on IE-2013-6996. A smaller individual from Walters Shoal (IE- 2013-6997), only a single spine was observed on the proximal-most basal carinal plate. Large (about 1.0 mm), paddle-shaped pedicellariae at the base of each spine and on adradials each sitting in a concave pit corresponding to the shape of each valve. Each plate with 13–30 peripheral granules, evenly distributed, quadrate in shape. Madreporite pentagonal, weakly concave with shallow sulci abutted by six round to polygonal plates.

Superomarginal and inferomarginal plates 32–42 per interradius (arm-tip to arm-tip) with 1:1 correspondence proximally with more zigzag correspondence distally along arm. Superomarginals wide, swollen, forming lateral border around disk periphery. Distalmost superomarginals, variably five to 10 pairs from terminus, abutted over mid radius. Two prominent conical spines present on three to five interradial superomarginal plates directed abactinally and dorsolaterally ( Figs. 7B, C ). Spine number decreases to one per plate along arms running in ordered serial formation with interradial spines. Superomarginal plates otherwise smooth, with no surficial accessories (e.g., granules, etc.). Peripheral granules 70–120 (mostly 80–100) surrounding each plate. One arm on holotype with substantive etching on superomarginal and inferomarginal surface. Inferomarginal plates wide interradially but becoming more elongate (L>W) distally along arm. Inferomarginal plates with one or two prominent, conical spines decreasing to a granular tubercle on some marginal plates with surface of inferomarginal plates irregularly covered by round to pointed granules, seven to nine ( Fig. 7C ). Irregularly one small paddle-shaped pedicellaria has also been observed. Terminal plate broadly triangular in shape.

Actinal surface composed of approximately three complete plate series in chevron formation ( Fig. 7D ). Each plate polygonal to quadrate in shape. One or two relatively large (1.0 mm length) paddle-shaped pedicellariae on each plate with a corresponding pit ( Fig. 7E ). Most pedicellariae with two valves, but exceptionally pedicellariae with three. Pedicellariae valves variable with some individuals showing smooth edges (i.e. IE-2013-6995) whereas others display jagged teeth on valves (i.e. IE-2013-6994, 6996). Pedicellariae in regular series along actinal series adjacent to adambulacral plates series. Most with a single pedicellaria per plate, but a minority of plates with two pedicellariae per plate, mostly present on proximal-most actinal plates adjacent to oral plates. Other than pedicellariae, actinal plates with round, densely packed but evenly spaced granules, 10–30 per plate surface.

Furrow spines eight proximally becoming 12 distally adjacent to arm-tip in straight to weakly curved fan on each adambulacral ( Fig. 7E ). Spines narrow, quadrate to angular in cross-section. Paddle-shaped pedicellariae present proximally on adambulacral plate surface. Adambulacral plates each with one or two large thick spines in transverse series each with heavily etched tips. Two spines present proximally gradually decreasing to single spine on arm tip. Transverse subambulacral spines approximately four times the thickness of an individual furrow spine and approximately three to four times the length forming prominent series along oral surface. Oral furrow spines 13–15, each oral plate surface half with one large spine identical to those on subambulacrals. Remaining oral plate surface mostly bare but distal end covered by 10–20 granules.

Color in life orange.

Material Examined. Holotype: IE-2007-1039 Madagascar 14°50’S 47°00E, 442 m, Coll. Bouchet & Kantor MIRIKY. 1 wet spec. R=10.9, r=3.2. Paratypes: IE-2013-6994 Madagascar 12°53’3’S 48°9’4’E, 480– 520 m. Coll. A. Crosnier 3 April 1971. P1 Chal. 2. 1 dry spec. R=8.6 r=2.2 . IE-2013-6995 Madagascar 12°43’0’S 48°13’4’E, 350– 360 m. Coll. A. Crosnier 15 April 1971. P3 Chal. 2. 1 dry spec. R=7.9 r=2.3 . IE-2013-6996 Madagascar. 12°42.4’S 48°14.3’E, 285– 295 m. Coll. A. Crosnier, 15 Sept. 1972, P3 Chalutage 42. 1 dry spec. R=7.7 r=1.9 . IE- 2013-6997 Walter’s Shoal , southern Indian Ocean. 33°11’S 44°00’E, 620– 635 m. Coll. Marion Dufresne 0 8 st. 6. CP 47. 16 March 1976. 1 dry spec. R=6.3 r=1.4

Figures

FIGURE 7. Calliaster sarahae n. sp. IE-2007-1039. R=10.9, r=3.2 cm. A. Abactinal surface. Scale bar=3.0 cm. B. Abactinal/ lateral view. Scale bar=3.0 cm. C. Superomarginal and inferomarginal plates showing spination. Scale bar=1.0 cm. D. Actinal view. Scale bar=3.0 cm. E. Closeup of adambulacral and furrow spines. Scale bar=1.0 cm.