Litonotaster gfoei, Mah, 2022

Mah, Christopher L., 2022, New Genera, Species and Occurrences of Deep-Sea Asteroidea (Valvatacea, Forcipulatacea, Echinodermata) collected from the North Pacific Ocean by the CAPSTONE Expedition, Zootaxa 5164 (1), pp. 1-75 : 53-56

Litonotaster gfoei n. sp.

FIGURE 18A–F

Etymology: The species epithet is named for the Global Foundation for Ocean Exploration whose efforts resulted in the collection of this very small and evasive species

Diagnosis. Body pentagonal (R/r=1.3). Abactinal plates irregular to polygonal in outline, with a bare central surface with irregularly shaped concavities surrounded by granules. Smaller plates and plates in the interradial regions are covered by granules. Papular pores, if present were not evident. Superomarginal and inferomarginal plates are identical in morphology and wider interradially. Superomarginals wide (W>L) with approximately 50% of surface (abactinal facing) bare in weakly circular pattern, lower half covered by coarse granules, 20–40 (mostly about 30). Inferomarginal plates with distinct cone-shaped spines present along actinolateral edge. Inferomarginal surface covered by coarse, round granules, 100–150, about 130–140 evenly distributed. Actinal plates covered by 3–20 short, pointed conical spinelets. Each plate irregular to polygonal in shape. Furrow spines four to six, tips blunt. Adambulacral plate surface with 7–20 short blunt spinelets similar to those on other actinal plate surfaces.

Comments. This species is placed within Litonotaster primarily based on the shape and arrangement of the abactinal and marginal plates. Many of the actinal accessories, primarily the granules are pointed as they are in the Atlantic Litonotaster intermedius .

This is the first species of Litonotaster which has been observed in situ and the second species to be recorded from the Pacific. Litonotaster gfoei n. sp. shows different characters that distinguish it from other Litonotaster spp. , including its pentagonal body shape (R/r=1.3) (others are more stellate), the presence of triangular or dagger-shaped spinelets on the actinolateral edge of the inferomarginal spines (others have conical spines or granules), and the apparent absence of pedicellariae (present on all other known species). Litonotaster gfoei n. sp. is most different from the Atlantic species, in that in addition to the differences, it and the East Pacific Litonotaster tumidus have significantly fewer furrow spines (four to six) versus five to eight in L. africans and L. intermedius .

Observations of in situ Litonotaster gfoei suggest that some characters on the abactinal surface appear differently on living specimens than on the post-collection specimen. Most notably the distribution of granules on the abactinal surface appear more evenly distributed on the in situ specimens versus the preserved specimen which shows numerous central bald areas on each plate ( Fig. 18A vs. 18B). The presence of these irregular bald spots on granulated abactinal plates is a variable character observed in Atlantic species of Litonotaster ( Halpern, 1969) .

When observed in situ , the numerous small spinelets in series around the actinolateral edge on the inferomarginal plates are prominent and directed outward ( Fig. 18B ) versus on the preserved specimen where they appear more loosely articulated.

Litonotaster gfoei n. sp. was never observed in abundance but it does appear to show a widespread distribution, ranging from Johnson Atoll and Musicians Seamount to the American Samoa region.

Ecological Comments. All the observations of this species (e.g. Fig. 18B ) were made of individuals on manganese encrusted hard rock substrata, which were almost always topped with light colored covering, thought to be either sediment or fallen organic flocculence (i.e. marine ‘snow’). Although the oral surface was not observed, it seems possible that this light-colored flocculence/sediment is food for this species.

Occurrence: American Samoa, Rose Atoll, Moki seamount, Utu seamount, Malulu seamount, Se Guyot , Johnson Atoll region, Mozart seamount, Musicians Seamount region , 2010–3708 m

Description. Body pentagonal (R/r=1.3), interradial arcs straight to weakly curved ( Fig. 18A ). Body thick. Arm tips distinct, upturned.

Abactinal plates flattened, trigonal, polygonal to round in outline, arranged irregularly. Proximal plates wider becoming smaller and more irregular in shape distally adjacent to superomarginals. Central surface of most plates bare with peripheral edges of each plate covered by round granules ( Fig. 18A and inset). Granules, 10–30, mostly 20, covering plates interradially especially at contact with superomarginal plates. Observations of living animals show the granules forming a more evenly distributed, bumpy texture with no bare regions ( Fig. 18B, G ). Carinal plates largest, especially distally adjacent to the arm tip with only a single peripheral series of granules, 20–40. Arm plates extend along arm tip to terminus. Most of distalmost arm plate surface bare. Plates weakly textured, not smooth. Weakly developed fasciolar groove present among distalmost plates. Living observations showed 3–30 papular openings per radial region ( Fig. 18G ). Images of the holotype in situ showed only one or two opening per radial region with larger plates flanking the papular pores ( Fig. 18B ). The holotype did not clearly display papular pores suggesting that they are cryptic or concealed, as only one or two pores were observed. Madreporite round flanked by approximately 10–12 abactinal plates. No pedicellariae observed.

Superomarginals 12, inferomarginals 16 per interradius (arm tip to arm tip) ( Fig. 18A ). Superomarginals and inferomarginals offset, contact in zig zag arrangement. Lateral side distinct ( Fig. 18A, B ). Superomarginals wide (W>L) with approximately 50% of surface (abactinal facing) bare in weakly circular pattern, bare surface becoming more narrower distalmost, widest interradially. Bare surface on superomarginals completely dominates surface on distal plates adjacent to terminal plates. Lower half of superomarginal plates covered by coarse granules, 20–40 (mostly 30) evenly spaced. Superomarginal edge with convex contact on abactinal plates. Peripheral granules, approximately 15–25 per side, approximately 30–80 around each superomarginal plate. Inferomarginals interradially squarish in outline, more elongate than corresponding superomarginal plate becoming narrower distally. Inferomarginals covered by coarse, round granules, 100–150, about 130–140 evenly distributed ( Fig. 18 C, D ). Central interradial inferomarginal plates each with one distinctly enlarged (approximately 2–3 mm wide) paddle-shaped pedicellariae. Actinolateral edge along inferomarginal plates distinct. Actinolateral edge on inferomarginal plates with flat, triangular spines, 7–15 per plate ( Fig. 18B, D ). Spines absent from distalmost inferomarginal plates. Similar triangular spines, 20–40, 50% of the width of those on the actinolateral edge, present on actinal surface of inferomarginal plates with large, round bald spot. Terminal plate diamond-shaped, surface bare.

Actinal surface in three complete series in chevron arrangement ( Fig. 18C, E ). Actinal plates covered by 3–20 short, pointed conical spinelets ( Fig. 18E ). Each plate irregular to polygonal in shape, plate series adjacent to adambulacrals rectangular in outline, quadrate, plates becoming smaller adjacent to inferomarginals, 7–10 plates in this series from oral plates to terminal plate. Furrow spines 4–6 ( Fig. 18F ), tips blunt. Adambulacral plate surface with 7–20 short blunt spinelets similar to those on other actinal plate surfaces. Oral plates each teardrop shaped with round convex edge facing onto actinal interradius. Each oral plate with ~20–28 short spinelets facing into the tube foot furrow. Oral plate with exposed surface with approximately 20–25 granules, with 10–15 short spinelets on paired contact with other oral plate in each interradius ( Fig. 18C ).

Color in life was yellowish-white ( Fig. 18B, G ).

Material Examined: Holotype. USNM 1453665 South Pacific, American Samoa. 14º26’S, 168º 38’W, 2457 m, Coll. NOAA Ship Okeanos Explorer w/ ROV Deep Discoverer EX 1702 . 27 Feb 2017. 1 wet spec. R =1.1 r=0.8.

Other Observations

Rose Atoll, American Samoa. -14.53769456, -168.0797401, 2522 m. EX1702 _IMG_20170218 T213444 Z_ ROVHD. jpg

Moki Seamount , American Samoa. -12.6491539, -167.2719078, 3709 m. EX1702 _IMG_20170221 T024422 Z_ ROVHD.jpg

Utu Seamount , American Samoa, -11.16771232, -169.8920979, 2011 m. EX1702 _IMG_20170223 T001435 Z_ ROVHD.jpg

Malulu, American Samoa- 14.46895286, -168.638811, 2456 m.

EX 1702_IMG_20170227 T 215926Z_ ROVHD.jpg

Southeast Guyot Ridge , Johnson Atoll region. 15.09190637, -167.9598986, 2448 m. EX1706 _IMG_20170728 T220107 Z_ ROVHD.jpg

Mozart Seamount, Musicians Seamount Chain. 28.9593602, -162.0713255, 2519 m EX1708 _IMG_20170920 T204701 Z_ ROVHD.jpg

Mozart Seamount, Musicians Seamount Chain. 28.96011009, -162.0714965, 2477 m EX1708 _IMG_20170920 T213447 Z_ ROVHD.jpg

Mozart Seamount, Musicians Seamount Chain. 28.96128436, -162.0715789, 2384 m EX1708 _IMG_20170920 T233345 Z_ ROVHD.jpg

Figures

FIGURE 18. Litonotaster gfoei n. sp. A. Abactinal view. Scale bar=2.0 mm. Inset showing surface detail. Largest individual plate diameter=1.0 mm. B. In situ image. Arrow showing inferomarginal spines extended, American Samoa, 2457 m. Scale bar=2.0 mm. C. Actinal view. Scale bar=2.0 mm. D. Actinal-Lateral view. Arrow showing spinelets on inferomarginal edge. Scale bar=1.0 mm. E. Actinal surface showing details. Scale bar=1.0 mm. F. Adambulacral spination, including furrow and subambulacral spines. Scale bar=0.75 mm. G. In situ image showing specimen with papular pores, Mozart Seamount, North Pacific.