Asteroschema cf. bidwillae McKnight, 2000

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/D2E2CB29-5574-57E2-8F3A-F1CB6054926A
treatment provided by	ZooKeys by Pensoft
scientific name	Asteroschema cf. bidwillae McKnight, 2000
status

Treatment

Asteroschema cf. bidwillae McKnight, 2000 View in CoL

Figures 8 View Figure 8 , 9 View Figure 9

Asteroschema bidwillae McKnight, 2000: 24-27, fig. 8.

Material examined.

China • 1 specimen; 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; IDSSE-EEB-SW0105 GoogleMaps .

Description.

Disc diameter 13 mm, length of arms 195 mm, arm base width 4.5-5 mm (Fig. 8 View Figure 8 ).

Disc. Disc circular, hexamerous, raised above arms, deeply swollen in center (Fig. 8A, B View Figure 8 ). Disc covered with dense, small, finely rugose granular epidermal ossicles (Fig. 8A-C View Figure 8 ). Granular ossicles dense and small in size in disc center, but slightly larger at distal edge (six or seven grains in 1 mm; Fig. 8C, D View Figure 8 ). Radial shields extending to center but proximal ends concealed by skin with granular ossicles, and distal ends raised above the disc (Fig. 8C View Figure 8 ). Granular ossicles around distal edge and periphery of disc larger and more irregular (Fig. 8C View Figure 8 ). Genital slits narrow, without ossicles and vertical on ventral interradii (Fig. 8E View Figure 8 ). Jaws elongated, mostly naked without granular ossicles (Fig. 8F View Figure 8 ). At apex of jaw flattened, pointed, and finely rugose teeth, and two to four granular tubercles that resemble lateral oral papillae (Fig. 8F View Figure 8 ). Ventral disc covered with widely separated small granular ossicles (four or six grains in 1 mm; Fig. 8B, F View Figure 8 ). Adoral shields connected to first ventral arm segment and concealed by widely separated small granular ossicles, but outline of shields clearly visible (Fig. 8F View Figure 8 ). Oral shields not discernible and adoral shield spine covered by ossicles (Fig. 8F View Figure 8 ).

Arms. Arms six, at base wide, not arched, dorsally flattened, and swollen in first few free arm segment (Fig. 8G View Figure 8 ). Arms distalwards from middle part narrowing and increasingly cylindrical (Fig. 8H View Figure 8 ). Swollen dorsal arm base covered with dense, large, irregular granular ossicles (four or seven grains in 1 mm), distalwards decreasing in size and becoming rounded (six or seven grains in 1 mm), and distally widely separated (Fig. 8G, H View Figure 8 ). Lateral arm plates covered with slightly separated granular ossicles. Ventral arm near base covered with granular ossicles similar to ventral disc (five or six grains in 1 mm), but becoming widely separated to completely naked along the arm (Fig. 8I, J View Figure 8 ). First two or three arm segments without arm spine (Fig. 8I View Figure 8 ). First arm spine appeared at third or fourth arm segment, and second arm spine at eighteenth or twenty-first segment (Fig. 8I-K View Figure 8 ). Inner arm spine cylindrical, with blunt thorny tip, one and a half arm segment in length (Fig. 8J, K View Figure 8 ). Outer spine half as long as inner spine in middle region, with thorny, pointed tip (Fig. 8K View Figure 8 ). Both arm spines equal in length at distal end of arm, and compound hook with 3-6 secondary teeth (Fig. 8L View Figure 8 ).

Color. In live specimen, reddish brown (Fig. 8 View Figure 8 ).

Ossicle morphology.

Lateral arm plate with two arm spine articular structures, with slightly separated large muscle and relatively small nerve opening (Fig. 9A View Figure 9 ). A depression on inner side of lateral arm plate (Fig. 9B View Figure 9 ). Inner arm spine from proximal and middle half of arm with cylindrical, terminal projection, and upper part of spine covered with thorns (Fig. 9C View Figure 9 ). Distally, arm spine turns into compound hook with secondary teeth (Fig. 9D View Figure 9 ). Arm and disc concealed by rounded to slightly irregular granular ossicles (Fig. 9E View Figure 9 ). Vertebrae with streptospondylous articulation, dorsally a median large longitudinal furrow, ventrally with median deep groove with lateral ambulacral canals, podial basins small (Fig. 9F-J View Figure 9 ).

Distribution.

400-2000 m depth. New Zealand, Tasman Sea, Solomon Islands, South China Sea ( OBIS 2021).

Remarks.

Asteroschema bidwillae was first described by McKnight (2000), with type locality New Zealand waters in the South Pacific Ocean. This is the first redescription since the original description. The specimens from our collection concur with McKnight’s description, but we noticed some differences such as: granular arrangement on radial shields, irregular ossicles on arm base, ossicles on ventral arm recorded nearly to middle region, and start of second arm spine. However, some of these variations may be related to size and maturity of the specimen (the holotype had a disc diameter of 5 mm). We hesitate to fully associate our specimen with Asteroschema bidwillae due to uncertainty with the morphological variation in A. bidwillae . The genus Asteroschema contains only two hexamerous species as far as known. Therefore, the closest one is Asteroschema wrighti McKnight, 2000, but it differs in characters of the radial shields, granulation on disc and arm, innermost arm spine, and start of second arm spine (Table 2 View Table 2 ). This is the first record of A. bidwillae from the North Pacific Ocean, if it is indeed this species.

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