Astrodendrum cf. sagaminum ( Doederlein , 1902)
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https://dx.doi.org/10.3897/zookeys.1090.76292 |
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lsid:zoobank.org:pub:3B13C71E-E11B-49D2-891C-050DBD514872 |
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https://treatment.plazi.org/id/0F632D74-B933-5921-9C03-B674FFFE18FD |
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Astrodendrum cf. sagaminum ( Doederlein , 1902) |
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Astrodendrum cf. sagaminum ( Doederlein, 1902)
Figures 20 View Figure 20 , 21 View Figure 21
Astrodendrum sagaminum Döderlein, 1902: 321-322; 1911: 38-39, figs 2, 3-5, 7, 8; 1927: 32, 92; H.L. Clark 1911: 292-293; A. H. Clark 1916a: 185; Liao 2004: 109-111, fig. 52.
Material examined.
China • 1 specimen; South China Sea , East side from Zhongsha Islands, seamount; 16°22.11'N, 116°06.60'E; depth 1619 m; 09 Aug. 2020; Collecting event: stn. SC028; ‘Shenhaiyongshi’ msv leg; preserved in -80 °C; GenBank: OK044304 View Materials ; IDSSE-EEB-SW0104 GoogleMaps .
Description.
Disc diameter 62 mm (Fig. 20A, B View Figure 20 ).
Disc. Dorsal disc slightly inflated, swollen in the center (Fig. 20A, B View Figure 20 ). Radial shields elongated, tapered at proximal end, extending to center of disc (Fig. 20C, D View Figure 20 ). Entire disc covered by skin with conical ossicles of various size (0.4-0.7 mm high) and widely separated and scattered (Fig. 20C-E View Figure 20 ). Genital slits conspicuous, interradial margin covered by two rows of higher than wide conical ossicles (Fig. 20F, G View Figure 20 ). Ventral disc almost naked, but micro-granular ossicles visible on oral region (Fig. 18H View Figure 18 ). Oral area covered by smooth skin with few scattered small granular ossicles, exposing adoral and oral shield outlines (Fig. 20H View Figure 20 ). Oral plates flat, polygonal, and slightly in contact with adoral shields (Fig. 20H View Figure 20 ). Adoral shields short, square. Oral papillae and teeth spiniform (Fig. 20H View Figure 20 ), several vertical rows of teeth on dental plate (possibly tooth papillae at ventral edge).
Arms. Arms branched at least eight to nine times, flexible dorso-ventrally, flat ventrally, arched dorsally (Fig. 20I-N View Figure 20 ). Ventral arm surface covered by smooth skin; proximal half with widely scattered small, flat, polygonal granular ossicles (Fig. 20I-K View Figure 20 ). Dorsal arm surface covered by polygonal or domed plates and between these pedicellarial bands (Fig. 20L-O View Figure 20 ) that appear after second arm fork, covering whole lateral to dorsal area of arm, creating annulated appearance (Fig. 20L View Figure 20 ). First arm segment lacks spines, next four to six with two arm spines, thereafter two or three arm spines per segment (Fig. 20I-K View Figure 20 ). Ventral arm spines similar in size, smaller, unevenly pointed, distally turning into hooks with 2-3 secondary teeth (Fig. 20K, P, Q View Figure 20 ).
Color. In live specimen, whole specimen brown, but radial shields, oral regions, and ventral arms lighter than disc (Fig. 20 View Figure 20 ).
Ossicle morphology.
On middle half of arm, lateral arm plates with perforations on ventral side, large muscle opening and small nerve opening (Fig. 21A View Figure 21 ). Pedicellarial bands formed by approximately 12 articulating tubercles at curved distal end of baseplate and these articulations have a single foramen per tubercle for pedicellariae with one secondary tooth (Fig. 21B, C View Figure 21 ). Ventral arm spines on distal end of arm transformed into hook with two or three secondary teeth (Fig. 21D View Figure 21 ). Pedicellariae differ from ventral arm spine by having smooth apophysis (Fig. 21C, D View Figure 21 ). Vertebrae with streptospondylous articulation with smooth lateral furrows and paired openings in lateral side of vertebrae for lateral ambulacral canals, no oral bridge (Fig. 21F-N View Figure 21 ).
Distribution.
90-1300 m depth. South China Sea, Japan, East China Sea, Sri Lanka.
Remarks.
The specimen is similar to the holotype description by Döderlein (1902), and the redescriptions of Döderlein (1911, 1927), Liao (2004) and Okanishi and Fujita (2018), but showed some morphological variations especially on the disc (Fig. 20 View Figure 20 ). Therefore, we hesitate to fully associate our specimen with Astrodendrum sagaminum . All descriptions mentioned granules on both dorsal and ventral disc, but in the present specimen, the dorsal disc is covered with widely separated conical stump-like granules and the ventral disc is covered with widely scattered micro-polygonal ossicle plates in naked skin. However, Baker (1980) mentioned that the granular pattern on the disc was not a suitable morphological feature to delimit species in the genus Gorgonocephalus . This is the first record of Astrodendrum sagaminum from the South China Sea, if this is indeed that species.
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.
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