Zatsepinia antarctica Schüller & Jirkov, 2013, n.sp.

Zatsepinia antarctica n.sp.

Figs 18–19

Holotype: ANDEEP III—st 81-8, EBS, 70°31.08'S – 70°32.23'S, 14°34.82'W – 14°34.90'W, eastern Weddell Sea, 4419 m [ZMH-26090].

Paratypes: ANDEEP III—st 80-9, EBS, 70°38.45'S – 70°39.18'S, 14°42.86'W – 14°43.43'W, eastern Weddell Sea, 3138 m (1 specimen, incomplete), ANDEEP III—st 81-8, EBS, 70°31.08'S – 70°32.23'S, 14°34.82'W – 14°34.90'W, eastern Weddell Sea, 4419 m (7 specimens, 1 x SEM, 3 complete) [ZMH-26091–26093].

Diagnosis: The species can be recognized by the dorsal shift of the last two thoracic notopodia, grooved and smooth buccal tentacles, 23–24 AUs, as well as a large pair of anal papillae.

Description: Holotype 5 mm long and 0.7 wide, with 24 AUs, complete. Complete paratypes and additional specimens 4–10 mm long and about 0.5 mm wide, with 23–24 AUs (Fig. 18 A). Colour in ethanol white. One specimen ovigerous, eggs spread throughout body cavity, most concentrated in posterior segments.

Prostomium simple, without lobes or glandular ridges (Figs 18 B, 18C, 19A). Nuchal organs present in posterior crest of prostomium (Fig. 19 B). Eyes absent. With [up to ten] thick, smooth and longitudinally grooved buccal tentacles, much thicker and some longer than branchiae (Fig. 18 A). Two pairs of branchiae in a transverse row, not separated by gap (Figs 18 B, 19A). Innermost branchiae connected to ТS-3, outermost to ТS-2. Branchiae smooth, with a dorsal longitudinal groove (Fig. 19 C). Outermost pair about half length of innermost pair. TS-2 without rudimentary notopodia. Paleae absent. 12 TCs, from TS-4. Notopodia of TC-1 smaller than subsequent ones and positioned somewhat dorsally. Notochaetae arranged in two rows with chaetae of anterior row about half length of posterior row, broadly winged in distal half, medially keeled (Fig. 19 C, D). 10 TUs present from TS-6. Neuropodia large, cushion-like tori. [Thoracic uncini with dental formula: MF-2-2-1-∞.] Notopodia of 2nd to last and last TCs shifted dorsally, dorsally connected by a ridge (Fig. 18 D). 24 AUs [23–24], from 3rd AU abdominal segments distinctly separate from each other. Abdominal rudimentary notopodia and cirri absent. Neuropodia of AU-1 and AU-2 similar to tori of thoracic neuropodia, situated on the body wall From AU-3 neuropodia more erect, with uncini at the outer margin of the pinnules. Abdominal uncini [dental formula: MF-2-2-2-∞]. Pygidium with a lateral pair of globular cirri (Fig. 18 E).

Nephridial papillae dorsal to notopodia in anterior TUs [mostly in TS-7 and 8]. Dorsally in TS-3 5 additional spherical papillae (Fig. 18 B).

Tubes made of fine sand and detritus, soft, without encrustations [sometimes with slightly developed growing lines, distance between them equal half tube diameter].

Remarks: The only other species of the genus Zatsepinia, Z. rittichae, was reported from Norwegian shelf waters. Zatsepinia is one of the few genera in Ampharetidae with two pairs of branchiae on TS-2 and -3 only. Zatsepinia rittichae possesses a simple prostomium, two pairs of branchiae, 12 TCs, 10 TUs and 17 AUs (Jirkov 1986; 2001; 2009), with the second to last thoracic notopodium shifted dorsally, and with paleae absent. Also, the species’ pygidium lacks paired papillae. Zatsepinia antarctica n.sp. shares the prostomial and thoracic characters. However, the last two thoracic notopodia are shifted dorsally in Z. antarctica n.sp., up to 24 AUs were observed in examined specimens, and the pygidum bears two prominent anal papillae. While the majority of specimens examined display 12 TCs, some specimens were found to bear chaetae in TS-3 also, resulting in a total of 13 TCs. These chaetae, however, were partially retracted, and much shorter and thinner than subsequent chaetae. If they were completely retracted, only the holes from which the chaetae protrude through the body wall were visible. These holes might have been overlooked in the remaining specimens under lower magnification. In consequence, Z. antarctica n.sp. might in fact bear 13 TCs starting from TS-3.

Etymology: The name refers to the type location of the species that are the Antarctic waters.