Freyastera delicata Zhang et al., 2019

Freyastera delicata Zhang et al., 2019 View in CoL

Figs 5 View Figure 5 , 14 D View Figure 14

Freyastera delicata View in CoL : Zhang et al. 2019: 2; Zhang et al. 2024: 10.

Material examined.

RSIOAST 0022 (holotype) . RSIOAST 0135 (Figs 5 View Figure 5 , 14 D View Figure 14 ). (Suppl. material 1) .

Diagnosis.

Arms six. Abactinal disk and arm plate each bears multiple spines (usually 4–8), most measuring 0.5–0.8 mm in length, not covered by membranous sheath. Pedicellariae absent on abactinal surface of disk and arm genital area. Pedicellariae cluster in transverse bands on abactinal arm beyond genital area. One long aboral spine and one subambulacral spine on each adambulacral plate. Proximal subambulacral spines with truncate end. Lateral spine corresponds to every adambulacral plate beyond genital area. Oral plate bears two actinostomal spines, one suboral spine, and one aboral furrow spine.

Distribution.

Northwest Pacific: Caiwei Seamount, O-Hakucho Guyot, 3121–4322 m. Type locality: Caiwei Seamount, 4322 m.

Remarks.

The species was described based on a single specimen (holotype RSIOAST 0022 ) ( Zhang et al. 2019). An additional specimen was examined in the present study, providing information on intraspecific variations of the species. The specimen RSIOAST 0135 (Fig. 5 View Figure 5 ) is smaller compared to the holotype, with maximum R = 135 mm, r = 4.1 mm, R / r ≈ 33. The arm measures 3.5 mm wide at the base, whereas the widest part of arm measures 4.6 mm. The genital area is about 9.5 mm in length. Gonads well-developed, female (Fig. 5 G View Figure 5 ). Abactinal arm spines slightly longer than those in the holotype, but not aligned in transverse rows as in the holotype (Fig. 5 D View Figure 5 ). The new specimen shares other characters with the holotype, including having no trace of pedicellariae on abactinal disk and genital area (Fig. 5 B, D View Figure 5 ), mouth plate with two actinostomal spines, one suboral spine, and one aboral furrow spine (Fig. 5 A View Figure 5 ), adambulacral plate with one subambulacral spine and one aboral spine pointing upwardly (Fig. 5 C, E View Figure 5 ), abactinal arm plate with several spines, and arm beyond genital area with transverse bands of pedicellariae (Fig. 5 H View Figure 5 ). The new specimen was found at 3121 m depth from O-Hakucho Guyot, close to the type locality (Fig. 1 View Figure 1 ), but is 1201 m shallower than the depth of the holotype (4322 m).