Astrodendrum capense
Creators: name: Okanishi, Masanori
name: Fujita, Toshihiko
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Echinodermata
Ophiuroidea
Euryalida
Gorgonocephalidae
Astrodendrum
Astrodendrum capense

description: Astrodendrum capense (Mortensen, 1933)
(Figs 8, 9)
Astroconus capensis Mortensen, 1933. 285–288, fig. 19a–e;— A. M. Clark & Courtman-Stock, 1976. 132. Astrodendrum capensis— Baker, 1980. 58; Alva & Vadon, 1989. 831, fig. 1c–d.
Type materials. ZMUC OPH-80, holotype, collected by Fisheries Survey, northeastern Durban, South Africa, 29˚51.00’S, 31˚28.00’E, 415 m deep, August 1929 (Fig. 1).
Diagnosis. External ossicles granular, fully in contact and large conical, separated on aboral disc; external ossicles plate shaped, fully in contact and conical, separated on interradial lateral disc; external ossicles plateshaped, fully in contact on oral surface of disc; bulges of lateral edges of proximal portion of arms absent; 2 or 3 terminal projections on each arm spine in proximal portion of arm; 1 or 2 secondary teeth on each hook-shaped arm spine in distal portion of arm.
Description of holotype. Disc. Disc five-lobed with notched interradial edges, 60 mm in disc diameter (Fig. 8A). Radial shields tumid (Figs 10A, C, D). Aboral disc entirely covered by small granular external ossicles, fully in contact, and large conical external ossicles, separated and scattered on radial shields and lateral marginal edge of disc (Fig. 8A, B, F). Granular external ossicles approximately 100–150 µm in length (Fig. 8E, F). The large conical external ossicles approximately 400–1300 µm in length on radial shields and 350–750 µm in length at lateral marginal edge of disc (Fig. 8F). Radial shields completely concealed by external ossicles, bar-like, approximately 12 mm in length, 3 mm in width, and almost reaching disc center (Fig. 8C). Oral surface of disc covered by flat, polygonal plate-shaped external ossicles, fully in contact, approximately 300–450 um in length (Figs 8G, H, 11A). Oral shields, adoral shields, oral plates and ventral arm plates completely concealed by external ossicles (Fig. 8G). Uniformly flat and spiniform teeth on dental plates, approximately 2.5–6 mm length and approximately 10 on each dental plate (Fig. 8H). Smaller acute and spine formed teeth on edge of each oral plate, approximately 1.2–2.0 mm in length and 12–14 in number (Fig. 8H). Interradial surface of lateral disc covered by flat plate-shaped external ossicles, fully in contact, and conical external ossicles, separated and scattered (Fig. 9B). Plate-shaped external ossicles approximately 100 um in length and granular external ossicles approximately 100–150 um in length (Fig. 9B). Two genital slits (4.6 mm long and 0.6 mm wide) in each interradius (Fig. 8B). Minute spinule ossicles along genital slits, 70–80 µm in length (Fig. 8B, E). One inconspicuous large, elliptical madreporite situated on an oral interradius, approximately 5 mm in length and 1.5 mm in height (Fig. 8G).
Arms. Arms five, branching at least 8 times but further branches interminate because of entanglement of arms (Fig. 8A, B). First branch occurring outside of disc (Fig. 8B). On the proximal portion of the arm, the width and height almost equal, 6.5 mm with an arched aboral surface and flattened oral surface (Fig. 8B). Arms tapering gradually towards arm tip (Figs 10B; 11C, D, F. F–H).
On aboral and lateral surface of the proximal portion of arm, each arm segment covered by plate-shaped external ossicles, fully in contact, approximately 150–200 µm in length (Fig. 9C). Hooklet-bearing plates inconspicuous, approximately 300 µm in length and separated, but not carrying hooklets before third branch (Fig. 9C), in contact and forming transverse rows after fourth branch (Fig. 9D). Throughout the arm, secondary hooklet present on hooklets. In middle portion of arm, aboral and lateral surfaces covered by plate-shaped external ossicles, fully in contact, approximately 120 µm in length (Fig. 9D, G). Oral surface of proximal portion of arms covered by flat, polygonal plate-shaped external ossicles, fully in contact, approximately 280–650 µm in length (Fig. 9E). In middle portion of arm, oral surfaces covered by flat, slightly tumid plate-shaped external ossicles, slightly in contact, approximately 100–180 µm in length (Fig. 9F). Those external ossicles disappearing on distal portion of the arms (Fig. 9H). Throughout arm, lateral and ventral arm plates completely concealed by skin or external ossicles (Fig. 8C–H). Tentacle pores small and almost invisible in external view (Fig. 8G). The first to third tentacle pores with no arm spine; fourth pores occasionally with 2 arm spines, fifth and subsequent pores with 3 (rarely 4) spines (Fig. 9F, G). In distal portion of the arm, the number of arm spines decreasing gradually to 1 toward arm tip (Fig. 9H). Arm spines on proximal portion of the arms ovoid, carrying 2 or 3 terminal projections. Innermost arm spines one-fourth the length of the corresponding arm segment, and outer spines two-thirds the length of inner spines (Fig. 9E). Arm spines on middle portion of arm cylindrical, carrying 2 terminal projections (Fig. 9F). Innermost arm spines half of length of corresponding arm segments, gradually decreasing in length to one-sixth length of corresponding arm segments toward outer spine (Fig. 9F, G). In the distal portion of arms, arm spines transforming into hooks with 2 secondary teeth, approximately two-thirds length of the corresponding arm segments (Fig. 9H).
Color. Uniformly white, interradial disc areas slightly darker (Fig. 8A, B).
Distribution. REPUBLIC OF SOUTH AFRICA. Off Durban, southeastern Africa (type locality, Mortensen, 1933). NAMIBIA. West off Namib-Naukluft National Park, southwestern Africa (Alva &Vadon, 1989; Olbers, 2016). Depth range 161–478 m (Fig. 1).
Remarks. Astrodendrum capense is related to A. elingamita in possessing small granular external ossicles, fully in contact on aboral disc. A. capense and A. elingamita can be distinguished by absence/presence of large conical spines on radial shields and the maximum number of secondary teeth on hook-shaped arm spines (Table 1, see also remarks for A. spinulosum sp. nov.).
description: Published as part of Okanishi, Masanori & Fujita, Toshihiko, 2018, A taxonomic review of the genus Astrodendrum (Echinodermata, Ophiuroidea, Euryalida, Gorgonocephalidae) with description of a new species from Japan, pp. 289-310 in Zootaxa 4392 (2) on pages 301-302, DOI: 10.11646/zootaxa.4392.2.4, http://zenodo.org/record/1195409