Asteroschema shenhaiyongshii, Nethupul & Stöhr & Zhang, 2022

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/A5459AA8-D154-47F1-833F-710652EF9636
taxon LSID	lsid:zoobank.org:act:A5459AA8-D154-47F1-833F-710652EF9636
treatment provided by	ZooKeys by Pensoft
scientific name	Asteroschema shenhaiyongshii
status	sp. nov.

Treatment

Asteroschema shenhaiyongshii sp. nov.

Figures 6 View Figure 6 , 7 View Figure 7

Material examined.

Holotype: China • 1 specimen; South China Sea, Northeast of Xisha Islands archipelago; 18°41.95'N, 113°33.08'E; depth 1070 m; 29 Mar. 2018; Collecting event: stn. SC004; ’Shenhaiyongshi’ msv leg; preserved in -80 °C; GenBank: OK044292, OL712208 ; IDSSE-EEB-SW0086. GoogleMaps

Paratype: China • 1 specimen; South China Sea , Southeast of Zhongsha Islands; 13°55.30'N, 115°25.44'E; depth 1111 m; 04 Aug. 2020; Collecting event: stn. SC007; ‘Shenhaiyongshi’ msv leg; preserved in -80 °C; IDSSE-EEB-SW0087 GoogleMaps .

Diagnosis.

Disc raised high above the arm, concealed by highly dense, small, rounded, finely rugose granular ossicles (Fig. 6A-C View Figure 6 ). Jaws narrow, elongated, concealed by slightly larger, less rounded granular ossicles (Fig. 6E View Figure 6 ). Arm surface concealed by granular ossicles similar to disc, but ventral surface of arm concealed by less rounded, more polygonal granular ossicles (Fig. 6F-H View Figure 6 ). Inner arm spine cylindrical, slightly club-shaped, with small sharp thorns on more than half its length (Fig. 6L-N View Figure 6 ).

Description of holotype.

Disc diameter 10 mm, length of arms 220 mm, arm base width 3.3-3.5 mm (Fig. 6 View Figure 6 ).

Disc. Disc more or less pentagonal, raised high above arm, and swollen in center (Fig. 6A View Figure 6 ). Entire disc concealed by highly dense, small, rounded, finely rugose granular ossicles (eight or nine grains in 1 mm; Fig. 6A-C View Figure 6 ). Granular ossicles similar in size and shape from center to periphery of disc (Fig. 6C View Figure 6 ). Radial shields wide, straight, close together, but not meeting in center, and completely concealed by dense granulation (Fig. 6C View Figure 6 ). Genital slits narrow, vertical at interradii and densely covered with less rounded granular ossicles (Fig. 6D View Figure 6 ). Jaws narrow, elongated, concealed by slightly larger less rounded granular ossicles (Fig. 6E View Figure 6 ). At apex of jaw a blunt, spearhead-shaped tooth, and granular ossicles all over oral plates (Fig. 6E View Figure 6 ). Ventral disc densely covered with granular ossicles similar to dorsal disc (seven or nine grains in 1 mm) but less rounded around distal end of jaw and adoral shields (Fig. 6E View Figure 6 ). Adoral shields large, with curved edge, and connected to first arm segment. Oral shields not discernible and adoral shield spine covered by granular ossicles (Fig. 6E View Figure 6 ).

Arms. Arm width comparatively large in relation to body size, not arched, sub-cylindrical, width unchanged from base to middle half of arm (Fig. 6A, F View Figure 6 ). From middle to distal end, arm tapering slightly and more cylindrical (Fig. 6F-H View Figure 6 ). Dorsal and lateral arm surface concealed by dense, finely rugose, rounded granular ossicles similar to disc (eight or nine grains in 1 mm), continuing to distal end of arm (Fig. 6F-H View Figure 6 ). Distal half of dorsal and lateral arm concealed by less rounded, dense granular ossicles (eight or nine grains in 1 mm; Fig. 6H View Figure 6 ). Lateral arm plates on proximal to middle half of arm concealed by granular ossicles, including on base of arm spine, but on distal end only lateral arm plates concealed (Fig. 6G-K View Figure 6 ). Ventral surface of arm concealed by dense granular ossicles, similar to ventral disc, less rounded and more polygonal, but only covering proximal half of arm (seven or nine grains in 1 mm; Fig. 6I View Figure 6 ). Middle to distal end of ventral arm surface concealed by widely separated, in size decreasing granular ossicles (three or four grains in 1 mm) to completely naked (Fig. 6J, K View Figure 6 ). First free tentacle pore without arm spine (Fig. 6I View Figure 6 ). First arm spine appears at second arm segment, with short blunt tentacle scale. Second arm spine appears at nineth or eleventh segment (Fig. 6I, J View Figure 6 ). Inner arm spine initially tapered to pointed thorny tip, one arm segment in length, middle half cylindrical, less club-shaped, with small sharp thorns on more than half of spine length (Fig. 6L-N View Figure 6 ). Outer spine smaller, with thorny tip (Fig. 6M, N View Figure 6 ). Both arm spines similar in size at distal end of arm, and turning into compound hook with 4-5 secondary teeth (Fig. 6O, P View Figure 6 ).

Color. In live specimen, reddish brown (Fig. 6 View Figure 6 ).

Ossicle morphology of paratype.

Lateral arm plate curved around the vertebrae, with two arm spine articular structures, with completely separate large muscle and nerve openings (Fig. 7A View Figure 7 ). A depression on inner side of lateral arm plate (Fig. 5B, C View Figure 5 ). Inner arm spine becoming cylindrical from proximal to middle half of arm, with terminal projection, and thorny surface on upper part of spine (Fig. 7D View Figure 7 ). Outer arm spine nearly half as long as inner one with less thorny tip (Fig. 7E View Figure 7 ). Distally both spines compound hook with 3-5 secondary teeth (Fig. 7F, G View Figure 7 ). Arm and disc concealed by rounded granular ossicles (Fig. 7H View Figure 7 ). Vertebrae with streptospondylous articulation, with deep slope between proximal and distal end, dorsally a median longitudinal furrow, ventrally with median deep longitudinal groove with lateral ambulacral canals, no oral bridge, podial basins moderate in size (Fig. 7I-M View Figure 7 ).

Paratype variations.

Paratype disc diameter 12 mm, similar to holotype. Second arm spine from segments 10-12 and disc slightly flatter than those of holotype; considered intraspecific variation.

Distribution and habitat.

1070-1111 m depth. Near Xisha and Zhongsha islands in the South China Sea. Attached to sponge host.

Etymology.

The specific name is dedicated to the manned submersible vessel ‘Shenhaiyongshi’ meaning deep sea warrior in Chinese, which collected the specimen.

Remarks.

Asteroschema shenhaiyongshii sp. nov. concurs with the group of Asteroschema that has only granular ossicles. This group includes nearly 20 species. Furthermore, they are divided by naked, widely separated granular ossicles on ventral disc and base of arm. Fifteen Asteroschema species have dense granular ossicles on the ventral disc. Asteroschema shenhaiyongshii sp. nov. is distinguished clearly by its unique dense, rounded, fine granular ossicles on both disc and arms, a thick sub-cylindrical proximal to middle half of the arms without annular bands, and cylindrical outer arm spine with visible thorns at middle arm segments (Fig. 7 View Figure 7 ).

Asteroschema ajax and A. laeve (Lyman, 1872) are similar to A. shenhaiyongshii sp. nov. by having granular ossicles on both dorsal and ventral disc, but are easily differentiated by well-spaced annulated granular bands on the arms, and club-shaped inner arm spine ( Clark A. H. 1949; Lyman 1875; FWRI 2010).

Asteroschema arenosum Lyman, 1878 is similar to A. shenhaiyongshii sp. nov. by having granular ossicles on both dorsal and ventral disc, but differs in having a swollen arm spine, sparser granular coverage (five grains in 1 mm), and a second arm spine from the fourth arm segment. Asteroschema vicinum Koehler, 1907 differs in its sub-equal arm spines and A. sulcatum Ljungman, 1872 in its highly dense granular ossicle coverage (9-15 grains in 1 mm). Asteroschema igloo and A. domogranulatum sp. nov. differ from A. shenhaiyongshii sp. nov. by large polygonal to domed granular ossicles (four or five grains in 1 mm; Table 2 View Table 2 ) ( Ljungman 1872; Lyman 1878; Koehler 1907; Pawson et al. 2009).

Asteroschema glaucum Matsumoto, 1915, and A. hemigymnum Matsumoto, 1915 are similar to A. shenhaiyongshii sp. nov. by having granular ossicles on both dorsal and ventral disc, but differ by sparser granular ossicle coverage (five or six grains in 1 mm), club-shaped inner arm spine at the middle arm segments and in A. hemigymnum the ventral disc is covered with pavement-like ossicles. Asteroschema inoratum Koehler, 1906 is similar to A. shenhaiyongshii sp. nov. by having a similar density of the granular coverage on both dorsal and ventral disc, but differs in having granular ossicles on the ventral surface along the arm, a slightly club-shaped inner arm spine at middle arm segments, and both spines not transforming into a compound hook (Table 2 View Table 2 ) ( Koehler 1906; Matsumoto 1915).

Asteroschema monobactrum H. L. Clark, 1917 is similar to A. shenhaiyongshii sp. nov. in having granular ossicles on both dorsal and ventral surface and in start of the second arm spine, but differs by having separate, sparser granular ossicles (seven grains in 1 mm at disc center, five or six grains in 1 mm at periphery of disc and on arm), and by the granular ossicles on both sides distalwards along the arm becoming widely separated to almost naked (H. L. Clark 1917). Asteroschema brachiatum Lyman, 1879 is similar to A. shenhaiyongshii sp. nov. in having similar density granular ossicle coverage on both dorsal and ventral disc and arms, but differs by the entire arm being covered by granular ossicles, start of the second arm spine at the fourth arm segment, and a slightly club-shaped inner spine at middle arm segments ( Lyman 1879). Asteroschema salix Lyman, 1879, A. tubiferum Matsumoto, 1911, and A. rubrum Lyman, 1879 differ from A. shenhaiyongshii sp. nov. by having separated, sparser granular ossicle coverage, a club-shaped inner spine at middle arm segments, and widely spaced ossicles on the ventral arm surface ( Lyman 1879; Matsumoto 1911).

Granular ossicle density of Asteroschema wrighti McKnight, 2000, A. bidwillae McKnight, 2000, and A. tenue (eight or ten grains in 1 mm) is similar to A. shenhaiyongshii sp. nov. However, Asteroschema tenue differs from A. shenhaiyongshii sp. nov. by having a club-shaped inner spine at middle arm segments, and slender long arms, and A. wrighti differs by having a club-shaped inner spine at middle arm segments, widely spaced granular ossicles on the ventral arm, irregular plate-like ossicles on the ventral disc, and smooth outer spines, and by being hexamerous (Table 2 View Table 2 ) ( Lyman 1875; McKnight 2000).

Most Ophiocreas species differ from Asteroschema shenhaiyongshii sp. nov. by having naked or micro-granular ossicles in the skin in both disc and arms. (Table 2 View Table 2 ). In our phylogenetic tree of the family Euryalidae , all Ophiocreas species cluster with some Asteroschema species, but the average genetic distance between Ophiocreas species and Asteroschema shenhaiyongshii sp. nov. was 13.61% (Fig. 2 View Figure 2 , Suppl. material 2: Table S2). Asteroschema shenhaiyongshii sp. nov. clusters among Asteroschema rubrum , A. salix , A. tubiferum , A. cf. lissum , and A. bidwillae . All these Asteroschema species have granular ossicles on the dorsal disc and dorsal surface of the arms. Asteroschema bidwillae showed a close relationship with A. shenhaiyongshii sp. nov., and was identified as a sibling species due to similar morphological characters of granular ossicles on the dorsal disc and dorsal surface of the arms, and the shape of the inner arm spines at middle arm segments, but differs by having well-spaced granular ossicles on the ventral disc, a naked proximal ventral arm surface, and by being hexamerous and fissiparous (Table 2 View Table 2 , Suppl. material 2: Table S2).