Asteroschema cf. lissum H. L. Clark, 1939

Nethupul, Hasitha, Stoehr, Sabine & Zhang, Haibin, 2022, Order Euryalida (Echinodermata, Ophiuroidea), new species and new records from the South China Sea and the Northwest Pacific seamounts, ZooKeys 1090, pp. 161-216 : 161

publication ID	https://dx.doi.org/10.3897/zookeys.1090.76292
publication LSID	lsid:zoobank.org:pub:3B13C71E-E11B-49D2-891C-050DBD514872
persistent identifier	https://treatment.plazi.org/id/07D71215-F3FD-5F08-9C88-ACF1CFA74132
treatment provided by	ZooKeys by Pensoft
scientific name	Asteroschema cf. lissum H. L. Clark, 1939
status

Treatment

Figures 16 View Figure 16 , 17 View Figure 17

Asteroschema lissum H. L. Clark, 1939: 37-39, figs 1-3.

Material examined.

China • 2 specimens; South China Sea , Zhongsha Islands, seamount; 13°36.20'N, 113°33.74'E; depth 1515 m; 30 Mar. 2020; Collecting event: stn. SC025; ‘Shenhaiyongshi’ msv leg; preserved in -80 °C; GenBank: OK044300 View Materials ; IDSSE-EEB-SW0079, IDSSE-EEB-SW080. Northwest Pacific • 1 specimen; near Mariana Trench, Southeast of GoogleMaps Guam Island, seamount, 12°6.67'N, 141°37.27'E; depth 1160 m; 03 Sep. 2019; Collecting event: stn. SC033; ‘Shenhaiyongshi’ msv leg; preserved in -80 °C; GenBank: OK044299, OL712207 ; IDSSE-EEB-SW0081 GoogleMaps .

Description.

IDSSE-EEB-SW0079: disc diameter 11.5 mm, length of arms 165 mm, arm base width 3-3.5 mm (Fig. 16 View Figure 16 ).

Disc. Disc flat, slightly raised above arms, swollen in center (Fig. 16A, B View Figure 16 ). Disc covered with smooth, small granular ossicles (Fig. 16C, D View Figure 16 ). Granular ossicles dense and small in disc center (six or eight grains in 1 mm), but slightly larger and separated at distal end of radial shield (five or six grains in 1 mm) (Fig. 16C View Figure 16 ). Radial shields wide, similar in size, curved, slightly raised above disc but not meeting in center (Fig. 16A, C View Figure 16 ). Radial shields clearly recognizable under thin skin embedded with ossicles (Fig. 16A, C View Figure 16 ). Genital slits narrow, concealed by polygonal granular ossicles, and vertical on ventral interradii (Fig. 16E View Figure 16 ). Jaws elongated, mostly naked without granular ossicles (Fig. 16F View Figure 16 ). Flattened, spearhead-shaped teeth, and six to seven granular ossicles that resemble lateral oral papillae at apex of jaw (Fig. 16F View Figure 16 ). Ventral disc covered with widely separated small granular ossicles (six or seven grains in 1 mm), but mostly covered by translucent thin skin (Fig. 16F View Figure 16 ). Adoral shields large, distal edge convex, concealed by thin skin with scattered small, smooth granular ossicles (Fig. 16F View Figure 16 ). Oral shields not discernible and oral tentacle pore naked without ossicles (Fig. 16F View Figure 16 ).

Arms. Arms slightly arched, circular, from middle to distal half narrower and more cylindrical (Fig. 16G View Figure 16 ). Dorsal arm base covered with granular ossicles similar to dorsal disc (six or eight grains in 1 mm), increasingly separated and decreasing in size along the middle segments of the arm (seven or eight grains in 1 mm), distally widely separated (five or six grains in 1 mm) (Fig. 16G, H View Figure 16 ). On lateral arm plates, granular ossicles widely separated but continuing to base of arm (Fig. 16H, K View Figure 16 ). Only one or three ventral arm segments near arm base covered with few granular ossicles similar to ventral disc (six or seven grains in 1 mm), then completely naked along the arm (Fig. 16I, J View Figure 16 ). First arm spine appears at second arm segment, second arm spine at ninth or thirteenth segment (Fig. 16I-K View Figure 16 ). Inner arm spine initially short, thick with thorny pointed tip, at middle arm cylindrical, taller, one and a half arm segment in length, with flattened thorny tip (Fig. 16J, K View Figure 16 ). Outer arm spine half as long as inner spine in middle region, with smooth to thorny tip (Fig. 16K View Figure 16 ). Both arm spines equal in length at distal end of arm, and compound hook with five or six secondary teeth (Fig. 16L View Figure 16 ).

Color. In live specimen, reddish brown but radial shields slightly lighter in color due to thin skin (Fig. 16 View Figure 16 ).

Ossicle morphology.

Lateral arm plate with two arm spine articular structures, with large muscle and nerve openings (Fig. 17A, B View Figure 17 ). Inner arm spine from proximal and middle half of arm cylindrical, with thorny tip (Fig. 17C View Figure 17 ). Distally, arm spine turns into compound hook with secondary teeth (Fig. 17D View Figure 17 ). Arm and disc concealed by less dense, wider, and short granular ossicles (Fig. 17E View Figure 17 ). Vertebrae with streptospondylous articulation, dorsally a median longitudinal furrow, ventrally with deep median longitudinal groove with lateral ambulacral canals, podial basins relatively small (Fig. 17F-J View Figure 17 ).

Distribution.

797-1515 m depth. Maldives, South China Sea, Northwest Pacific.

Remarks.

Asteroschema lissum was first described by H. L. Clark (1939), with type locality Maldives waters in the Indian Ocean. This is the first redescription after the original description. The specimens from our collection were close to H. L. Clark’s description but we noticed some differences, such as: characters of radial shields, and granular ossicles at ventral disc and base of arm. We hesitate to fully associate our specimens with Asteroschema lissum or propose a new species, due to uncertainty of these morphological variations. Some of these variations may be affected by size, maturity, and environment (holotype disc diameter 7.5 mm). Asteroschema lissum strongly resembles A. hemigymnum , A. intectum , and A. sublaeve by having similar granular density, and almost naked ventral disc and arms but differs in characters of the radial shields, start of second arm spine, granulation pattern on the disc and arm (Table 2 View Table 2 ). This is the first record of A. lissum from the South China Sea and the North Pacific Ocean, if it is indeed this species.

Kingdom	Animalia
Phylum	Echinodermata
Class	Ophiuroidea
Order	Euryalida
Family	Euryalidae
Genus	Asteroschema