Linckia profunda, Mah, 2021

Mah, Christopher L., 2021, The East Pacific / South Pacific Boundary: New taxa and occurrences from Rapa Nui (Easter Island), New Caledonia and adjacent regions, Zootaxa 4980 (3), pp. 401-450 : 429-430

Linckia profunda n. sp.

Figures 12A–G

Etymology. The species epithet “ profunda ” alludes to the deep bathymetric range of this species.

Diagnosis. This species is characterized by irregular plate patterns along abactinal arm surface, ranging from a flattened to convex (bumpy) surface, displaying 8 to 15 papular pores. Ambulacral furrow spines two per plate, alternating large and small along the length of the arm. Subambulacral spines set off from furrow spines by distinct junction, widely spaced by approximately the distance of the small furrow spine between the two larger ones. Arms elongate, R/r=R/r=6–12.5, mostly 10–12.5. Color in life is bright orange to dark reed with dark highlights on the abactinal side, yellow to light orange on oral surface. Furrow spines are white to straw colored.

Comments. This species displays closest resemblance to Linckia gracilis Liao, 1985 , sharing an identical irregular, abactinal plate surface and plate type, a comparable number and marginal plate shape as well as a similar number of papulae, a single madreporite and furrow and subambulacral spines that are similar in shape.

Linckia profunda n. sp. however differs in several respects, the furrow spines are heterogeneously (small and large) sized along most of the arm versus L. gracili s which possesses homogeneously sized furrow spines along its arm length. Linckia profunda n. sp. lacks the scale-like granules which form the periphery around each adambulacral plate observed in L. gracilis .

Linckia profunda n. sp. also invites comparison with Linckia guildingi , which shows similar subambulacral spine morphology and location (subambulacrals directly adjacent to the furrow spines). Similar to L. guildingi , L. profunda n. sp. also has furrow spines, which are alternatively large and small, but only a single row of subambulacral spines which are circular in outline, whereas L. guildingi has two subambulacral spine series, which are more oval to bean-shaped in outline.

The Atlantic Linckia bouvieri shows adambulacral spination similar to that observed in Linckia profunda n. sp. with alternating large and small furrow spines and a single series of large-sized subambulacral spines. However, the subambulacrals in L bouvier are much more elongate and have more distinct, flattened abactinal plates than those on L. profunda n. sp.

Habitat comparisons. Linckia profunda n. sp. is one of the deepest known species of a genus known primarily from shallow water settings. It is perhaps surprising, that in spite of the popular association of species such as Linckia laevigata with shallow-tropical Pacific reef habitats, in fact, most species of Linckia actually occur at relatively deep depths. Linckia gracilis from the East China Sea is known from 100– 200 m. The Atlantic species, Linckia nodosa and L. bouvieri occur between 9 and 475 m. The most widely occurring species, Linckia guildingi from both Atlantic and Indo-Pacific oceans has been recorded from between intertidal to 298 m depths ( Clark & Downey 1992). Shallow water Linckia ., including L. columbiae , L. laevigata and L. multifora generally occur at depths shallower than 50 m.

Description. Body strongly stellate (R/r=6–12.5, mostly 10–12.5) but arms unequal in length among specimens examined. Disk small, thick, arms tapering, round in cross-section. Interradial arcs acute.

Abactinal plates abutted, individual plates flattened to convex (bumpy). Carinal series indistinct, abactinal plates irregularly arranged throughout most of arm distance with plates along distalmost arm tip forming ordered or weakly ordered rows. Distalmost plates also with most strongly convex plates. Papular pores 3 to 20, mostly 8 to 15 present irregularly throughout abactinal arm surface between convex plates. Abactinal, marginal, actinal surface covered by close-set polygonal granules, approximately 5–7 counted along a 1.0 mm line, occurring as a dense, continuous layer obscuring plate boundaries. Madreporite single, variably quadrate to peanut shaped in outline, flanked by 4 to 8 abactinal plates. Pedicellariae not observed. Anus located on raised region, centrally on disk flanked by approximately four to five granules, then approximately eight plates.

Marginal plates comprised of superomarginal, intermarginal and inferomarginal plate series. Although marginal plate series are mostly complete, approximately two arms (four lateral arm surfaces) display prominent disjunctions with all marginal plate interruptions formed by irregular jumbles of abactinal and marginal plate series. Superomarginals round in shape, convex, approximately 120–160 per interradius (60–80 per arm), abutted along arm series, in direct contact proximally becoming separated and interrupted by granular plates more distally

Intermarginal papular regions offset from superomarginal and inferomarginal plates, 120–160 per interradius (60–80 per arm) each contain 0 to 12 papulae, each pore, circular in shape. Intermarginal surface relatively flat compared to convexity observed on superomarginal and inferomarginal plates. Papulae abundance highest proximally decreasing to one and then no papulae adjacent to terminal plate. Inferomarginal plates identical in shape and number with superomarginals, running in direct parallel with superomarginal plates. Terminal plate broadly diamond shaped with rounded edges, weakly convex, with smooth surface.

Actinal surface composed of 4 to 6 linear series, crossed by transverse depressions forming a wrinkled appearance around the oral and proximal arm regions. Every two transverse depressions aligned with an inferomarginal plate extending to adambulacral region. Actinal granulation part of continuous granular cover present on abactinal and marginal surface, relatively coarse formed by approximately 3 granules along a 1.0 mm line. Individual actinal plates weakly convex, quadrate in shape, but plate boundaries are obscured by granulation. Granulation along adambulacral plates/adjacent to adambulacral spination forms linear grain parallel to tube foot groove relative to granulation along actinal surface which occurs in perpendicular/transverse quadrate series. Adambulacral granulation mostly homogeneous, but at approximately the 40th–50th adambulacral plate a large smooth granule-like tubercle, approximately two to three times the ambient granules is present.

Furrow spines two per adambulacral plate, inset along tube foot furrow so that spines sit within the furrow with only tips extending to body surface, each spine blunt, quadrate in shape, broadly rectangular in cross-section. Proximal spines identical in size, each spine broadly identical with subambulacrals in size, but beginning at approximately the fifth or sixth adambulacral spine, furrow spines are sharply heterogeneous in shape with the proximalmost spine becoming approximately 50% the thickness of the other furrow spine on the plate. Furrow spines alternate small and large along arm series to the terminus. Subambulacral spines, broadly quadrate in cross-section with round edges, blunt tipped, low. Each subambulacral spine similar in size to larger of the two furrow spines per plate. Subambulacral spines adjacent to furrow spines variably closely adjacent (in CASIZ 222377) or slightly distant or offset (in CASIZ 222374). It is unclear how mobile these spines are or if their relative distance is related to size. Approximately two or three blunt spines on oral plate with a single spine projecting into mouth. Three large, thick but smooth spines present on oral plate surface. Some subambulacral spines present on actinal intermediate region on granular regions adjacent to oral plate surface.

Color in life is bright orange to dark reed with dark highlights on the abactinal side, yellow to light orange on oral surface. Furrow spines are white to straw colored.

Material described. Holotype: CASIZ 222374 . Rapa Nui ( Isla de Pascua), off Hanga Piko, 110 m. Coll Bart Shepherd, Tyler Phelps & Luis Rocha, 3–7 March 2017. 1 wet spec R =6.4, r=0.6.

Paratypes: Rapa Nui : CASIZ 222376 . Moto Nui , Rapa Nui (Isla de Pascua), 82.2 m. Coll. Bart Shepherd, Tyler Phelps & Luis Rocha, 6 May 2017, 2 wet specs. R =6.6, r=0.8; R =7.8, r=1.3. CASIZ 222377 . Moto Nui , Rapa Nui (Isla de Pascua), 76.2 m. Coll. Bart Shepherd, Tyler Phelps & Luis Rocha, 5 May 2017. 1 wet spec. R =12.5, r=1.0. New Caledonia: MNHN IE-2016-1535 (EcAs 12470). Norfolk Ridge , New Caledonia, 23º44′S, 168º01′E, 229– 428 m. Coll. B. Richer, ORSTOM 23 Nov. 1996, 1 wet spec. R =9.9, r=0.8. MNHN IE-2016-1536 (EcAs 12455). Kaimon Maru Bank , South New Caledonia, 24º46.7′S, 168º08.3′E, 254– 283 m. Coll. LITHIST DW 11, Coll. Richer, IRD, 11 Aug. 1999, 1 dry spec. R =4.5, r=0.4 (arms of varying lengths). MNHN IE-2016-1537 (EcAs 12451). Antigonia Bank , Norfolk Ridge, New Caledonia, 23º18′S, 168º01′E, 540 m. Coll. NORFOLK 1 DW 1722, Coll. , Lozouet, Boisselier & Richer, IRD, 26 June , 2001, 1 dry spec. R =4.5, r=0.5. MNHN IE-2016-15378 (EcAs 12452). Antigonia Bank , Norfolk Ridge, New Caledonia, 23º23′S, 168º02′E, 180– 250 m. Coll. NORFOLK 1 DW 1712, Coll. , Lozouet, Boisselier, Richer, IRD, 26 June , 2001, 1 dry spec. R =10.0, r=1.0 (2 arms damaged). MNHN IE-2016-1531 . New Caledonia , 22°18′S, 168°42′E, 340 m. Coll. EXBODI CP 3898, 20 Sept. 2011, 1 wet spec. R =10.6, r=1.1. MNHN IE-2016-1542 (ex EcAh 4832). Jumeau-West Bank , Norfolk Ridge, New Caledonia, 23º40′S, 168º01′E, 234– 261 m. Coll. by Lozouet, Boisseller, Richer, IRD, st. CP 1668, 21 June 2001, 3 wet spec. R =3.7, r=0.5; R =2.9, r=0.4; R =8.3, r=0.8. MNHN IE-2016-1541 (ex EcAh 4799). Antigonia Bank , Norfolk Ridge, New Caledonia, 23º22′S, 168º03′E, 257– 269 m. Coll. Lozouet, Boisselier, Richer, IRD, NORFOLK 1 DW 171426 June , 2001. 7 wet specs. R =6.1, r=0.6; R =4.6, r=0.4; R =5.5, r=0.5; R =6.3, r=0.7; R =3.5, r=0.4; R =2.3, r=0.3; R =2.1, r=0.3. MNHN IE-2016-1540 (ex EcAh 4822). Antigonia Bank , Norfolk Ridge, New Caledonia, 23º22′S, 168º02′E, 204– 216 m. Coll. NORFOLK 1 DW 1713, Coll. , Lozouet, Boisselier, Richer, IRD, 26 June , 2001, 1 wet spec. R =7.6, r=0.8. MNHN IE-2016-1539 (ex EcAh 5019). Kaimon Maru Bank , South New Caledonia, 24º45′S, 168º09′E, 231– 233 m. Coll. Lozouet, Richer, IRD, NORFOLK 1 , DW 167522 June 2001, 2 wet specs. R =7.3, r=0.9; R =5.1, r=0.8. MNHN IE-2016-1543 (ex EcAs 12129). South New Caledonia , 23º41′S, 168º01′E, 240– 300 m. Coll. BERYX 11 , DW40, B. Richer ORSTOM aboard N/O Alis. 20 Oct. 1992. 1 dry spec. R =5.2, r=0.6. MNHN IE-2016-1544 (ex EcAs 12129). South New Caledonia , 23º40′S, 168º01′E, 270– 290 m. Coll. B. Richer ORSTOM, BERYX 11 , CP45 aboard N/O Alis. 20 Oct. 1992. 1 dry spec. R =9.8, r=1.0. MNHN IE-2013-9434 . New Caledonia , 22°53′S, 167°37′E to 22°55′S, 167°37′E, 290– 310 m. Coll. KANACONO, DW4744, Coll. 23 Aug. 2016, 1 wet spec. R =6.1, r=0.6.

Figures

FIGURE 12. Linckia profunda n. sp. Holotype CASIZ 222374 (Rapa Nui): A. Abactinal. Scale bar equals 1.0 cm. B. In situ observation of holotype. Photo by Dr. Luiz Rocha. C. Lateral view. Scale bar equals 0.5 cm. D. Close-up of abactinal surface. Scale bar equals 0.5 cm. E. Actinal view. Scale bar equals 1.0 cm. F. Furrow spines. Scale bar equals 0.2 cm. G. Oral view. Scale bar equals 0.5 cm.