Echinopsolus onekotanensis Panina, Stepanov, Smirnov & Martynov, 2020

Panina, Elena G., Stepanov, Vadim G., Smirnov, Alexei V. & Martynov, Alexandr V., 2020, Two new species of holothurians of the genus Echinopsolus Gutt, 1990 (Echinodermata: Dendrochirotida: Cucumariidae) from the North-Western Pacific, Zootaxa 4789 (1), pp. 233-246 : 238-239

Echinopsolus onekotanensis Panina, Stepanov, Smirnov & Martynov sp. nov.

( Figs 6–11 )

Psolidae gen. sp. 2— Stepanov & Panina 2015: 47.

Holotype. RAS, Cat. No. 477-485, male, specimen 49 mm long, G.B. Elyakov Pacific Institute of Bioorganic Chemistry Institute of the Far Eastern Branch of the Russian Academy of Sciences , 16 August 1982, Onekotan Island (Kuril Islands), 49°28′ N, 154°35′ E, 100 m depth, trawler-seiner “Dalarik”, trawl. No further specimens known.

Type locality. Onekotan Island (Kuril Islands).

Etymology. The species name is derived from the type locality.

Diagnosis. Color in life is light pink, in alcohol, white. The mouth and anus are displaced to the dorsal side. The ventral side flattened like a sole. The skin is thick and wrinkled on the dorsal side. Ventrolateral tube feet are well developed (4-5 tube feet in transverse rows). In mid-ventral radius tube feet are only found at the oral end. Tube feet near the mouth on the dorsal side are arranged in the following pattern: five small tube feet near the mouth and four larger ones distally. Tentacles 10, ventral pair smaller than others. Ossicles of the body wall are globules and perforated plates. Ossicles of the tube feet are globules, perforated and multi-layered network plates.

Description of the holotype. Length— 49 mm, width— 33 mm, height 10 mm to the top of mouth cone, 5 mm up to the anus cone ( Fig. 6 ). Color in life light is pink (personal communication of V.I. Kalinin, PIBOC FED RAS) in alcohol, white. The mouth and anus are displaced to the dorsal side. The ventral side is flat like a sole. The skin is thick and wrinkled on the dorsal side. Ventrolateral tube feet are well developed (4-5 tube feet in transverse rows). In mid-ventral radius tube feet are only found at the anteriorly end: three tube feet in four rows. A few tube feet are located near the mouth on the dorsal side: five small tube feet near the mouth and four larger ones distally. Ten tentacles present, the ventral pair of which is smaller than the others. Retractors are attached to longitudinal muscles at a distance 1/3 from anterior end. Gonads are well developed, consisting of the two tufts of the light yellow gonadal tubules.

Polian vesicle, madreporic and stone canal are absent.

The calcareous ring with 10 segments is simple, low with short posterior processes ( Fig. 7 ). Radial segments of calcareous ring have a deep posterior notch and a tall posterior projection which is narrow in the middle. Interradial segments of the calcareous ring are lower than the radials, and have a shallow posterior notch, and a low anterior projection.

Ossicles of the dorsal side are compact round globules form with a rough structure (diameter 233–566 µm; Fig. 8 ) and three-dimensional crosses ( Fig. 9 ). Ossicles of the ventral side are lacey globules (diameter 96–161 µm; Fig. 10 A, D, F, C ), flat plates with few holes and knobs (length 113–174 µm; Fig. 10 B ), crosses ( Fig. 10 E ), and multilayered mesh-like plates. Ossicles of the tentacles are perforated plates with or without knobs: flat ( Fig. 11 A, B, C ) or curved ( Fig. 11 E, F, G, I ), multi-layered mesh-like plates ( Fig. 11 D ) and crosses ( Fig. 11 H ). Ossicles of the tube feet are lacey globules ( Fig. 12 A ), flat perforated plates with or without knobs ( Fig. 12 B ) and multi-layered mesh-like plates ( Fig. 12 C ).

Figures

FIGURE 6. Echinopsolus onekotanensis: A—side view, B—top view, C—ventral view (Photo of K.E. Sanamyan).

FIGURE 7. Echinopsolus onekotanensis. Segments of the calcareous ring (R—radial segment, IR—interradial segment). Dotted line—attachment of retractor.

FIGURE 8. Echinopsolus onekotanensis. Scanning electron microscope images of a globule of the dorsal body wall.

FIGURE 9. Echinopsolus onekotanensis. Scanning electron microscope images of a three-dimensional cross of the dorsal body wall.

FIGURE 10. Echinopsolus onekotanensis. Scanning electron microscope images of ossicles of the ventral body wall: A, D, F—globules, B—perforated plates, C—baskets, E—cross.

FIGURE 11. Echinopsolus onekotanensis. Scanning electron microscope images of ossicles of the tentacles: A, B, C—flat perforated plates, E, F, G, I—curved perforated plates, D—multi-layered mesh-like plates, H—cross.

FIGURE 12. Echinopsolus onekotanensis. Ossicles of the tube feet: A—globules, B—perforated plates, C—multi-layered mesh-like plates.