Neosabellaria uschakovi Kirtley 1994

Neosabellaria uschakovi Kirtley, 1994

Figs. 1 (A–C), 2 (A–F), 3 (A–F).

Neosabellaria uschakovi - Kirtley, 1994: 25.

Material examined. Two paratypes, USNM-38577, Sea of Japan, Tartar Strait, Sta. 20/ 2206, coll. by Okhriamkin, 1931, Zoological Institute of the Academy of Sciences, USSR, Accession Number 278429.

Description. One paratype 35 mm long, 5.0 mm wide at widest part of opercular crown, 5.0 mm wide at parathoracic chaetigers, ca. 35 abdominal chaetigers (middle parts damaged), incomplete, cauda ca. 3.0 mm long and bent backwards on ventrum. Another paratype incomplete, posterior abdomen missing, abdominal chaetigers 20, body length 30 mm, head region ca. 8.0 mm long, body width 5.0 mm at parathoracic chaetigers. Body of preserved worms light brown.

Anterior end of opercular stalk completely fused, not separated into two lobes (Fig. 2 A, B); in lateral view narrowing anteriorly, sloping posteriorly towards dorsal midline. Operculum dish-shaped, flat to slightly concave.

Paleae bright yellow or light brown, arranged in three concentric circlets of palea, the outer, the middle, and the inner (Fig. 2 D, E). Outer paleae weakly curved outward from longitudinal axis of shaft, 70 and 77 in number, blade ca. 1.0 mm long, ca. 0.2 mm wide (Figs. 2 B-E, 3 A, B). Inner surface of their blades with ca. 40 to 50 fine closely-spaced thecal bands, with 3–5 distal teeth on either side of a pilose plume (Figs. 1 B, 2 D, E, 3 A, B). Middle paleae of long and short kinds in irregular alternating rows; 4 short and 19 long in one of two paratypes (Fig. 2 C) and of a single long form and 36 short forms in another (Fig. 2 D), with blades of long forms with compressed vertically, weakly recurved blunt tips. Inner paleae geniculate, obovate, their anterior ends with pointed tips. Nuchal spines not observed.

Anterior outer margin of opercular crown with 18–20 fleshy conical papillae in single row on each side (Fig. 2 A, B). Ventral margin of bucal cavity with over 50 longitudinal rows of feeding tentacles on each side. Building organ U-shaped, with conical cirri, forming upper lip on ventral side.

Three parathoracic chaetigers with oar-shaped chaetae and spine-like companion chaetae in 2 or 3 rows on each neuropodium with 10 chaetae. Abdominal region with at least 22–25 chaetigers. Dorsal branchiae present in parathoracic and anterior-most ca. 10 abdominal chaetigers. Dorsal branchiae diminishing in size posteriorly, with horizontal rows of cirri.

Variation. In the original description, Kirtley (1994) described the paleae of middle series with alternating long, curving nearly vertical blades (Fig. 1.6.b of Kirtley 1994: 25) and shorter blades with broad, slightly concave upper surface and rounded, rugose distal margins (Fig. 1.6c of Kirtley 1994: 25). But in two paratypes observed here, middle paleae arranged in alternate rows, varying from 1 to 19 long paleae per row and from 4 to 36 short paleae per row (Fig. 2 D, E). Eyespots not observed in preserved specimens. Unfortunately, we were not able to obtain the holotype to compare its trunk characters with those in paratypes described here.

Tube. No complete tubes were available for examination, only debris from tube fragments were present in the vial.

Type locality. Far Eastern Seas of Russia, Tartar Strait, the Sea of Japan.

Distribution. Far Eastern Seas of Russia (Bering Sea, Sea of Okhotsk, Sea of Japan).

Remarks. Neosabellaria uschakovi is a unique species of the genus in having two kinds of the middle paleae arranged in irregular alternating rows; other six species have only one kind of middle paleae (Bailey- Brock et al. 2007). The exact number of long and short middle paleae varied in each individua more than described by Kirtley (1994).