Asteromorpha capensis ( Mortensen, 1925 )

Okanishi, Masanori, Olbers, Jennifer M. & Fujita, Toshihiko, 2013, A Taxonomic Review Of The Genus Asteromorpha Lütken (Echinodermata: Ophiuroidea: Euryalidae), Raffles Bulletin of Zoology 61 (2), pp. 461-480 : 462-467

publication ID	https://doi.org/ 10.5281/zenodo.4508609
persistent identifier	https://treatment.plazi.org/id/44116F51-FFA8-FF85-C564-4AD1FDACC23E
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scientific name	Asteromorpha capensis ( Mortensen, 1925 )
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Asteromorpha capensis ( Mortensen, 1925) View in CoL

( Figs. 2–5 View Fig View Fig View Fig View Fig )

Astroschema capensis Mortensen, 1925: 152–155 View in CoL , pl. VIII figs. 4–5, text-fig. 5; 1933: 221, 227 (new combination)

Asteroschema capensis View in CoL . A. M. Clark & Courtman-Stock, 1976: 130; Sink et al., 2006: 469–470

Asteroschema capense . Okanishi & Fujita, 2009: 116, 119, 123, 125; 2011: 149

Type material examined. — Dry holotype of Astroschema capensis, DNSM ECH 1, ca. 29–32 km (18–20 miles) off Umvoti River Mouth , eastern South Africa, ca. 64–73 m (35–40 fathoms), Nov.1920 ( Fig. 1) .

Other material examined. — Two dry specimens, USNM 1201805 View Materials , Anton Bruun Ridge , northeast coast of Somalia, Madagascar , 11°37'S, 51°27'E, Anton Bruun Stn 465, 67– 72 m, 18 Dec.1964; one ethanol preserved specimen, deposited in Echinoderm Collection at MNHN, south Madagascar GoogleMaps .

Diagnosis. — External ossicles on aboral surface of the body plate-shaped, polygonal, tessellated. No regular transverse rows of external ossicles on aboral and lateral surface of the arms. Body reddish purple with creamy white spots on aboral disc and white bands on aboral and lateral surface of the arms, or body light brown aborally and white orally. No tubercles on radial shields. Five arms, non-fissiparous.

Description of USNM 1201805. — Disc diameter 6.3 mm, arm length ca. 34.5 mm ( Fig. 2 View Fig ).

Disc five-lobed with notched interradial edges, no obvious fission plane. On aboral surface, radial shields and their surroundings tumid ( Fig. 2A View Fig ). Aboral surface of disc covered by slightly domed and polygonal plate-shaped external ossicles ( Fig. 2 View Fig A–C), ca. 100 μm long and 80 μm thick on periphery ( Fig. 2B View Fig ), and ca. 70 μm long and 80 μm thick on central area ( Fig. 2C View Fig ). Radial shields tumid, ca. 1.25 mm long and 0.60–1.25 mm wide ( Fig. 2A View Fig ) and completely covered by external ossicles.

Oral surface of disc entirely covered by flat and round plateshaped external ossicles, ca. 70 μm long and 60 μm thick on periphery ( Fig. 2D, E View Fig ) and ca. 100 μm long and 100 μm thick on oral plates ( Fig. 2D, F View Fig ). Four square teeth forming a vertical row on dental plate ( Fig. 2F View Fig ). Six to seven domed oral papillae lying on each side of the jaw ( Fig. 2D, E View Fig ).

Lateral interradial surface of disc nearly vertical, covered by flat and round plate-shaped external ossicles similar to those on oral surface, ca. 50–80 μm long ( Fig. 2G View Fig ). Two genital slits in each interradius, 0.90 mm long and 0.30 mm wide. One oral interradial bulge present suggesting the presence of at least one madreporite plate.

Arms simple, five in number, no abrupt reduction in width of arms. Distal arms tapering gradually. Basal portion of arms 2.0 mm wide and 2.1 mm high, square in cross-section. Aboral surface arched and oral surface flattened from middle to distal portion of arms.

Basal portion of arms completely covered by slightly domed and polygonal plate-shaped external ossicles, ca. 100 μm long and 70 μm thick on aboral and lateral surface ( Figs. 2H View Fig , 4A, B View Fig ) and ca. 70–80 μm long and 50 μm thick on oral surface ( Fig. 3A View Fig ). These ossicles densely tessellated ( Figs. 2H View Fig , 3A View Fig ). In the middle portion of arms, aboral and lateral surface covered by plate-shaped external ossicles, similar to those on basal portion of arms ( Fig. 3B View Fig ), ca. 70–80 μm long and 70 μm thick. Oral surface covered by flat and round granule-shaped external ossicles, ca. 40–50 μm long and 50 μm thick ( Fig. 3C View Fig ). In distal portion of arms, aboral and lateral surface covered by flat and round granule-shaped external ossicles, ca. 50 μm long and 20 μm thick ( Figs. 3D View Fig , 4C, D View Fig ). External ossicles on oral surface gradually decreasing in size distally becoming absent near arm tips ( Fig. 3E View Fig ).

First to third tentacle pores lacking arm spines; fourth pores with one arm spine and from fifth pores, two arm spines ( Fig. 3A View Fig ). In first third of arms, arm spines ovoid and minute ( Fig. 4H View Fig ). Inner arm spines ca. one-third to half length of corresponding arm segment, while outer arm spines slightly shorter. In second third of arm, arm spines bear fine spinelets at tips ( Fig. 4I View Fig ). Inner arm spines ca. two-thirds length of corresponding arm segment, while outer arm spines almost same length as inner ones ( Fig. 3C View Fig ). In distal third of arms, arm spines hook-shaped with smooth lamina on distal side ( Fig. 4J View Fig ). Inner arm spines three quarters length of corresponding arm segment, while outer arm spines almost same length as inner ones.

Lateral arm plates concealed by external ossicles, with pairs of a muscle and nerve openings, associated with each arm spine articulation ( Fig. 4E View Fig ). Vertebrae with oral bridge from distal third on arms ( Fig. 4F, G View Fig ).

Colour: Uniformly light brown aborally and uniformly white orally ( Fig. 3A, D View Fig ).

Ossicle morphology of DNSM ECH1. — Disc diameter 8 mm, arm length ca. 50 mm.

Vertebrae in distal portion of arms with oral bridge ( Fig. 4K View Fig ).

Variation. — Some colour variations were observed across the four specimens. Holotype and one alcohol preserved MNHN specimen have white spots on aboral disc and bands on aboral and lateral surface of the arm ( Fig. 5 View Fig ) but the two dry specimens ( USNM 1201805 View Materials ) do not have such spots.

Distribution. — MADAGASCAR: south and northeast of Madagascar (present study); SOUTH AFRICA: off Umvoti River, 64–73 m ( Mortensen, 1925).

Remarks. — Mortensen (1925) described the present species as Asteroschema of present Asteroschematinae based on external observations. The holotype of Astroschema capensis deposited in the Durban Natural Science Museum has oral bridge on oral side of vertebrae of distal portion of arms ( Fig. 4K View Fig ) and two arm spines from fifth arm segment ( Fig. 5C View Fig ). These morphological features confirm an affiliation with the Euryalinae ( Mortensen, 1933; Okanishi et al., 2011). Body being covered mostly by external ossicles and the distal arm spines having a smooth basal lamina support this species’ placement in the the genus Asteromorpha . Thus, here we conclude that Asteroschema capense should be transferred to the genus Asteromorpha of Euryalinae .

Asteromorpha capensis ( Mortensen, 1925) can be distinguished from the other species of Asteromorpha by its morphological characters: flat and polygonal plate-shaped external ossicles that are densely tessellated on aboral body; a body that is either reddish purple with creamy white spots on aboral disc and banded aboral and lateral surfaces of the arms, or light brown aborally and white orally; radial shields that lack tubercles; and five arms, showing no signs of fissiparity. See also remarks under A. rousseaui for a detailed account of these taxonomic characters ( Table 1).