Astrodia abyssicola (Lyman, 1879)

Xie, Xiaojun, Lu, Bo, Pang, Jie & Zhang, Dongsheng, 2022, Description of two species of the genus Astrodia Verrill, 1899 (Ophiuroidea, Euryalida, Asteronychidae), including a new species from seamounts in the West Pacific, ZooKeys 1123, pp. 99-122 : 99

publication ID	https://dx.doi.org/10.3897/zookeys.1123.87397
publication LSID	lsid:zoobank.org:pub:DF436107-268C-4011-9D57-02B8C83C35ED
persistent identifier	https://treatment.plazi.org/id/6318B1AF-001E-5BE3-A22D-1E19EC49DFBE
treatment provided by	ZooKeys by Pensoft
scientific name	Astrodia abyssicola (Lyman, 1879)
status

Treatment

Figs 8 View Figure 8 , 9 View Figure 9 , 10 View Figure 10 , 11 View Figure 11 , 12 View Figure 12

Ophiocreas abyssicola Lyman, 1879: 64-65, plate 17, figs 470-473.

Astrodia abyssicola : Okanishi and Fujita 2014: 188-192, figs 2-4.

Material examined.

China • 1 specimen; Philippine Sea , Kyushu-Palau Ridge, Mugiboshi Seamount; 16.57.14'N, 134.52.7'E; depth 3225 m; 11 August 2021; collected by an HOV JIAOLONG; preserved in alcohol; RSIO68002 .

Description.

Disc pentagonal and almost flat, 10 mm in diameter, 3.2 mm in height, skin wrinkled under dry conditions (Fig. 9A, B View Figure 9 ). Aboral surface of disc lacks external ossicles (Fig. 9A, B View Figure 9 ). Radial shields narrow, slightly tumid, bar-like, without granules or spines, and almost reaching center of disc. (Fig. 9A View Figure 9 ). Approximately 3.8 mm long and 0.6 mm wide in center and 0.8 mm wide on periphery (Fig. 9A View Figure 9 ).

Oral surface flat, covered by thin skin, and lacking external ossicles (Fig. 9C View Figure 9 ). Oral shield triangular, one madreporite (Fig. 9D View Figure 9 ). Adoral shield big and thick, quadrangular, and longer than wide (Fig. 9D View Figure 9 ). Teeth spearhead-shaped, vertically on dental plate; each jaw bears a pair of short, conical oral tentacles (Fig. 9C View Figure 9 ). Oral papillae indistinct or underdeveloped (Fig. 9C View Figure 9 ). Two genital slits very short, 560 μm long and 110 μm wide, present on oral side of each interradius. Gonads visible in each interradius (Fig. 9D View Figure 9 ).

Five arms, long and slender, about nine to ten times as long as disc diameter, no abrupt change in width basally (Fig. 9E View Figure 9 ). Proximal portion of arm 1.8 mm wide and 420 μm high, with arched aboral surface and flattened oral surface. Arms tapering gradually toward tip. Arm spines only present in ventral part of arm. First to third tentacle pores without arm spines, fourth tentacle pores with one arm spine and following tentacle pores with two arm spines. Inner arm spines longer than outer arm spines. On middle and distal part of arm, outer arm spines three-fourths as long as inner spines (Fig. 9F View Figure 9 ). Three arm spines occurred once in two of the five arms. Lateral arm plates not projecting on arms.

Color. Bright pink in situ, entirely white in alcohol (Fig. 8B, C View Figure 8 ).

Ossicle morphology . Vertebrae articulation streptospondylous, wider than long in proximal segments (Fig. 10A, B View Figure 10 ), longer than wide in distal segments (Fig. 11A, B View Figure 11 ). Oral side of each vertebra with longitudinal groove along midline, deeply depressed, and no oral bridge (Figs 10C View Figure 10 , 11C View Figure 11 ). Pair of podial basins on oral side moderate in size (Figs 10C View Figure 10 , 11C View Figure 11 ). Aboral side of each arm vertebra with longitudinal aboral groove,moderately depressed (Figs 10D View Figure 10 , 11D View Figure 11 ). Lateral furrow of vertebrae declining obliquely from aboral to oral side (Figs 10E, F View Figure 10 , 11E, F View Figure 11 ). Lateral arm plates crescent-shaped, each associated with one or two arm spines. Spine articulations with separated nerve and muscle openings, bulging outwards (Fig. 12A, C View Figure 12 ). A ridge on inner side of lateral arm plate (Fig. 12D View Figure 12 ). Arm spines cylindrical, never hooked, bearing fine thorns at apex throughout arms (Fig. 12E, F View Figure 12 ).

Remarks.

Ophiocreas abyssicola was first described by Lyman (1879). Okanishi and Fujita (2014) transferred O. Ophiocreas abyssicola to the genus Astrodia and redescribed it. This specimen (RSIO68002) was identical to Astrodia abyssicola by having 0~2 arm spines, rather short genital slits and crescent-shaped lateral arm plates. However, this specimen lacks external ossicles on the disc and arms, which is different from previous descriptions of Astrodia abyssicola by Okanishi and Fujita (2014) as having plate-shaped external ossicles on the periphery. Nevertheless, the genetic distance of COI and 16S (2.9% and 1.9%) between the new collected specimen and A. abyssicola are too small to justify two different species. Therefore, this specimen was identified as A. abyssicola , thus the external ossicles on the aboral surface of the disc could be plate-shaped or absent in this species.