Freyastera jiaolongi, Zhang & Zhou & Mao & Wang & Zhang, 2025

Zhang, Ruiyan, Zhou, Yadong, Mao, Jingwen, Wang, Chunsheng & Zhang, Dongsheng, 2025, Hidden diversity of Freyastera (Asteroidea, Brisingida, Freyellidae) at great depth: Description of new species and remarks on species boundaries, Zoosystematics and Evolution 101 (2), pp. 735-760 : 735-760

Freyastera jiaolongi sp. nov.

Figs 2 , 3 , 4 , 14 A – C

Freyastera sp. 4 : Zhang et al. 2024.

Material examined.

Holotype. RSIOAST 0117 (Figs 2 , 3 ), Kyushu-Palau Ridge ; 12.330671°N, 134.472114°E, 3523 m; 16 Nov. 2021; cruise DY 68, dive JL 199 . Paratype 1. RSIOAST 0112 (Fig. 3 A, D ), Kyushu-Palau Ridge ; 13.309640°N, 134.591983°E, 3641 m; 13 Nov. 2021; cruise DY 68, dive JL 197 . Paratype 2. RSIOAST 0113 (Fig. 3 B, C, E, F ), Kyushu-Palau Ridge ; 13.310851°N, 134.589032°E, 3541 m; 13 Nov. 2021; cruise DY 68, dive JL 197 . All type specimens were deposited at the Repository of Second Institute of Oceanography, Ministry of Natural Resources, China ( SIOMNR) (Suppl. material 1).

Diagnosis.

Arms six. Abactinal disk with short hirsute spinelets, about 0.2 mm in length, surrounded by small pedicellariae. Abactinal arm plates each bears one spine, covered with a membranous sheath loaded with small pedicellariae. Pedicellariae on abactinal disk and arm less than 0.1 mm in length. Pedicellariae cluster in pads or transverse bands on abactinal arm beyond genital area. Each adambulacral plate with 1–3 aboral furrow spines and one subambulacral spine. Lateral spines long, corresponding to each adambulacral plate beyond genital area. Oral plate with 1–2 actinostomal spines, one suboral spine, and one aboral spine along the furrow margin.

Description.

Holotype: a complete specimen, with one arm regenerating. r = 5.5 mm, R about 220 mm. Height of disk 3.5 mm. Arm measures 4 mm at base, 6 mm at the widest part. Genital inflation extends about 13.5 mm. Female. Paratypes: RSIOAST 0112 & RSIOAST 0113 , disks absent, seven detached arms mixed in one jar. Longest arm measures about 230 mm. Arm 4.1 mm wide at base, 4.7 mm at the widest part. Genital inflation extends about 16 mm. Female.

Abactinal surface of disk with small rounded plates, each with one short spinelet measuring about 0.2 mm in length (Fig. 2 B ). At the base of the spinelets is a circle of 2–6 small pedicellariae, less than 0.1 mm in length. Spinelets are more crowded and longer at center of the disk, where the anus located but obscured by a cluster of spinelets. Madreporite with a subcentral cleavage, 1.3 mm in diameter, rather large and protruding, situated near the interradial margin of the disk above the odontophore. The surface of madreporite also covered with spinelets and small pedicellariae.

Basal part of arm with slight genital inflation. A pair of gonads to each arm. Female gonads encapsulated in a long sac, about 13 mm in length (Fig. 4 D ). Abactinal armature of arm in the genital area with irregular polygonal-shaped plates, much larger than those on disk (Fig. 2 D ). Each plate carries one short spine, about 0.5–0.8 mm in length, covered with a tegument loaded with minute pedicellariae (Figs 2 D , 3 A , 4 A, B ). A minority of larger plates carry two or even three spines. The surface of arm plates also scattered with small pedicellariae. The abactinal plates do not seem to go far beyond genital area. The spines become shorter at the end of genital area, sheathed with pedicellariae-covered tegument (Fig. 3 B, C ). Beyond genital area, the pedicellariae cluster in round tegumentary pads (Fig. 3 D ). At the distal part of the arm, pedicellariae pads or transverse bands occur alternately (Figs 3 E, F , 4 F ).

Adambulacral plate narrow and elongated (Figs 2 C, E , 4 C ). Each bearing one central subambulacral spine and 1–3 small aboral furrow spines. Furrow spines at the base of arm measure less than 1 mm in length, covered with a few scattered small pedicellariae and usually a tuft of pedicellariae at the tip. Furrow spines become fewer and smaller at middle to distal part of arm (Fig. 4 E ), then disappear. Subambulacral spines sheathed, covered with dense small pedicellariae. Subambulacral spines about 2–2.5 mm in length at base of arm, 4–5 mm at middle part of arm. The first inferomarginal plate occurs at about the 7 th adambulacral plate, corresponding to alternate or every third adambulacral plate within the genital area and then to every adambulacral plate beyond about 20 th adambulacrals. Inferomarginal plates each bear one long sheathed lateral spine, similar in form to subambulacral spines but much longer, about 20 mm in length at middle part of arm.

Oral plate with 3–4 spines in total (Fig. 2 A ). One or two actinostomal spines along the proximal margin of the plate, about 1 mm in length. One suboral spine, the most robust of all oral spines, 1.5–2 mm in length, situated not at the center of the plate but near the proximal-furrow margin. One aboral spine similar in size to the actinostomal spine, siting at the distal furrow margin of the plate. All mouth spines with pointed or obtuse tips, covered with minute pedicellariae.

A small crustacean skeleton found in the mouth of the holotype (Fig. 2 A ).

Etymology.

Named after the Chinese manned submersible Jiaolong that collected all three specimens of the new species.

Distribution.

Northwest Pacific: Kyushu-Palau Ridge. 3523–3641 m.

Remarks.

The new species is morphologically most similar to the type species of the genus, Freyastera sexradiata , in the armature of abactinal arm plate, adambulacral plate, and oral plate. It differs from F. sexradiata mainly in the armature of abactinal disk. In F. sexradiata (r = 6 mm), the abactinal surface of disk bears “ fairly elongated spines, ” and pedicellariae are absent from the disk ( Perrier, 1894). In the new species (r = 5.5 mm), the abactinal surface of disk is equipped with small hirsute spinelets, about 0.2 mm in length, which are circled by numerous small pedicellariae. The two species are also geographically distant (Fig. 1 ). F. sexradiata is known from the North Atlantic, whereas the new species is distributed in the Kyushu-Palau Ridge in the Philippine Sea. Genetically, the new species is close to another undescribed species, Freyastera sp. 5 (COI distance 2.64 % – 3.52 %). The latter was not described here as only fragmented arms were collected, but in these arm fragments, none of the adambulacral plates bear any furrow spines, which is distinguishable from the new species.

Figures

Figure 1. Distribution of Freyastera and six-armed Freyella specimens examined in the present study and type localities of each species.

Figure 2. Freyastera jiaolongi sp. nov. holotype RSIOAST 0117. A. Actinal view of disk; B. Abactinal view of disk; C. Actinal view of arm in genital area; D. Abactinal view of arm in genital area; E. Actinal view of middle part of arm; F. Actinal view of distal part of arm.

Figure 3. Freyastera jiaolongi sp. nov. holotype RSIOAST 0117. A – D. Abactinal view of arm, from basal part to beyond genital area; E. Abactinal view of middle part of arm; F. Abactinal view of distal part of arm.

Figure 4. Freyastera jiaolongi sp. nov. paratypes. A, D. RSIOAST 0112; B, C, E, F. RSIOAST 0 AS 113. A, B. Abactinal view of arm in genital area; C. Actinal view of arm in genital area; D. Female gonads; E. Actinal view of middle part of arm; F. Abactinal view of middle part of arm.

Figure 14. In situ photos of Freyastera species. A. Freyastera jiaolongi sp. nov. holotype RSIOAST 0117; B. Freyastera jiaolongi sp. nov. paratype RSIOAST 0112; C. Freyastera jiaolongi sp. nov. paratype RSIOAST 0113; D. Freyastera delicata RSIOAST 0135; E. Freyastera basketa RSIOAST 0200; F. Freyastera sp. 5 RSIOAST 0116; G. Freyastera sp. 5 RSIOAST 0107; H. Freyastera sp. 6 RSIOAST 0124; I. Freyastera sp. 6 RSIOAST 0125.