Asterostegus tuberculatus Mortensen, 1933

Okanishi, Masanori & Fujita, Toshihiko, 2014, A taxonomic review of the genus Asterostegus (Echinodermata: Ophiuroidea), with the description of a new species, European Journal of Taxonomy 76, pp. 1-18 : 12-17

publication ID	https://doi.org/ 10.5852/ejt.2014.76
publication LSID	lsid:zoobank.org:pub:01BEFFB2-2E53-4B1E-A7BC-36702313BBF8
DOI	https://doi.org/10.5281/zenodo.3851747
persistent identifier	https://treatment.plazi.org/id/03917D3B-D90F-F762-B718-7E1AFD550D2A
treatment provided by	Tatiana
scientific name	Asterostegus tuberculatus Mortensen, 1933
status

Treatment

Asterostegus tuberculatus Mortensen, 1933 View in CoL

Figs 7-10 View Fig View Fig View Fig View Fig

Asterostegus tuberculatus Mortensen, 1933: 298-300 View in CoL , figs 24-25, pl. 19; figs 4-5.

Asterostegus tuberculatus View in CoL – Okanishi & Fujita 2013: 568, 572, 575, fig. 1, tables 2-3.

Diagnosis

Tubercles present on periphery of radial shields as well as interradial periphery of disc, ca. 350 µm long. On proximal portion of arm, two or three tubercles on top of each lateral bar. Five to eight oral interradial plates forming two rows.

Material examined

SMNH-123461, one ethanol preserved specimen, west coast of Reunion Island, 500 m, 2009.

Description

MEASUREMENTS. SMNH-123461: disc diameter 14.5 mm, arm length 259 mm.

DISC. Disc circular in shape, with notched interradial edges ( Fig. 7A View Fig ). On aboral surface, radial shields and their surrounds tumid ( Fig. 7A View Fig ). Disc surface covered by skin and evenly scattered tubercles ( Fig. 7A-C View Fig ). Tubercles on disc center granule-shaped, ca. 300 µm diameter and 400 µm height ( Fig. 7C View Fig ) and on periphery club-shaped tubercles, ca. 350 µm diameter and 550 µm height ( Fig. 7B View Fig ). Radial shields, ca. 7.5 mm long and 0.7-2.0 mm wide ( Fig. 7A View Fig ), completely covered by skin and tubercles. Oral surface of the disc covered by skin and granule-shaped external ossicles, ca. 120-240 µm diameter, which are evenly scattered ( Fig. 7D, F View Fig ). Four spearhead-shaped teeth form a vertical row on dental plate ( Fig. 7E View Fig ). Six to seven domed oral papillae lie on each side of jaw ( Fig. 7E View Fig ). Adoral shields somewhat hexagonal-shaped ( Fig. 7F View Fig ). Oral interradial plates pentagonal or hexagonal-shaped, in two rows ( Fig. 7G View Fig ). Proximal row consists of two oral interradial plates, distal row consists of three interradial plates ( Fig. 7G View Fig ). Lateral interradial surface of disc nearly vertical, covered entirely by skin ( Fig. 7H View Fig ). Two genital slits in each interradius, 4.1 mm long and 0.7 mm wide ( Fig. 7H View Fig ). One madreporite present between oral side of genital slits ( Fig. 7H View Fig ).

ARMS. Arms simple, five in number, with no abrupt gap in width due to presence of gonads in proximal portion of arms. Arms tapering gradually distally. Proximal portion of arms 6.85 mm wide and 5.5 mm high, oblong in cross-section. Aboral surface arched and oral surface flattened from middle to distal portion of arms. Proximal portion of arms covered by skin and two or three club-shaped tubercles, ca. 400 µm long and 750 µm height ( Figs 7I View Fig ; 8J-K View Fig ), on each lateral bar. On middle portion of arms, tubercles granule-shaped, ca. 450 µm long ( Fig. 9A View Fig ), one or two on each lateral bar. On oral surface, four to five granule-shaped external ossicles, scattered on each arm segment, ca. 150-300 µm long on proximal portion of arms ( Fig. 9C View Fig ) and ca. 100-150 µm long on middle portion of the arms ( Fig. 9D View Fig ). Tubercles and external ossicles on oral surface gradually decrease in size distally, becoming absent near arm tips ( Fig. 9B, E-F View Fig ). First to third tentacle pores lacking arm spines; two arm spines from fourth pore ( Fig. 7D View Fig ). In proximal third of arms, arm spines ovoid and minute ( Figs 8G View Fig ; 9C View Fig ). Outer arm spines ca. two-thirds as long as corresponding arm segment, inner arm spines slightly shorter, ca. two-thirds as long as outer spine ( Fig. 9C View Fig ). In middle of arm, arm spines club-shaped ( Figs 8H View Fig ; 9D View Fig ). Inner and outer arm spines of equal length, ca. half as long as corresponding arm segment ( Fig. 9D View Fig ). In distal third of arms, arm spines hook-shaped with smooth lamina on distal side ( Fig. 9E View Fig ). Inner and outer spines of equal length, ca. one-third as long as corresponding arm segment ( Figs 8I View Fig ; 9E-F View Fig ). Lateral arm plates concealed by skin and external ossicles, with two pairs of muscle and nerve openings, and each of them associated with an arm spine articulation ( Fig. 8A-F View Fig ). Ventral lobes and dorsal lobes beside muscle openings meet ( Fig. 8 View Fig C-D). A condyle present between each muscle and each nerve opening ( Fig. 8C, D View Fig ). Vertebrae with streptospondylous articulations ( Fig. 10A, E View Fig ), oral bridges on oral side ( Fig. 10A, C, E, G View Fig ), knobs on lateral side ( Fig. 10B, D, F, H View Fig ). These features indicate A. tuberculatus ’ affiliation to the family Euryalidae . Knobs on lateral side of vertebrae elongate throughout the arms ( Fig. 10B, D, F, H View Fig ).

COLOUR. Uniformly white, slightly grayish on aboral disc surface except radial shields ( Fig. 7A View Fig ). Black spots appear on aboral and lateral arms randomly, every 2-20 arm segments ( Fig. 7I View Fig ). Colour in life is unknown.

Distribution

Off Durban, 376 m depth, Republic of South Africa (type locality, Mortensen 1933b). Off Reunion Island, 500 m depth (present study).

Remarks

Asterostegus tuberculatus can be distinguished from the other two species in the arrangement of tubercles on the disc, numbers of tubercles on lateral bars, and the arrangement of oral interradial plates ( Table 1 View Table 1 , see also the Remarks for the other two species).