Noanelia orensanzi Schüller & Jirkov, 2013, n.sp.

Noanelia orensanzi n.sp.

Figs 16–17

Holotype: ANDEEP I–II—st 134-4, EBS, 65°19.20'S – 65°19.05'S, 48°3.81'W – 48°2.92'W, central Weddell Sea, 4069 m [ZMH-26078].

Paratypes: ANDEEP I–II—st 134-4, EBS, 65°19.20'S – 65°19.05'S, 48°3.81'W – 48°2.92'W, central Weddell Sea, 4069 m (2 specimens, 1 complete), ANDEEP III—st 21-7, EBS, 47°39.87'S – 47°38.52'S, 04°15.79'E – 04°14.94'E, South Africa / South Atlantic, 4574 m (5 specimens, 1 x SEM, all complete), st 78-9, EBS, 71°09.52'S – 71°09.34'S, 14°00.76'W – 13°58.85'W, eastern Weddell Sea, 2182 m (1 specimen, complete), 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 (2 specimens, all complete), st 102-13, EBS, 65°33.18'S – 65°34.32'S, 36°33.24'W – 36°31.05'W, transect eastern to central Weddell Sea, 4817 m (1 specimen, complete), st 121-11, EBS, 63°38.27'S – 63°37.31'S, 50°37.16'W – 50°38.04'W, Central Weddell Sea, 4698 m (2 specimens, all complete), st 142-5, EBS, 62°11.36'S – 62°11.36'S, 49°27.62'W – 49°29.57'W, central Weddell Sea, 3403 m (1 specimen, incomplete), st 150-6, EBS, 61°49.13'S – 61°48.52'S, 47°27.51'W – 47°28.16'W, South Orkney Islands, 1970 m (4 specimens, all complete), st 153-7, EBS, 63°19.82'S – 63°19.18'S, 64°36.44'W – 64°37.53'W, King George Island, 2014 m (7 specimens, 1 x SEM, all complete) [ZMH-26079–26089].

Diagnosis: The species can be distinguished from the type species of the genus, N. hartmanae (Desbruyères & Laubier, 1977), by its different proportion of branchial length, the position of nephridial papillae in TS-6 to 8, and dorsally shifted notopodia in the last two TCs.

Description: Holotype 5 mm long and 0.8 wide, with 13 AUs, complete (Fig. 16 A). Complete paratypes and additional specimens 1.5–7.5 mm long and 0.1–1 mm wide, with 8–12 AUs. Some ovigerous, eggs distributed throughout whole body cavity, but concentrated in pouch-like structures above abdominal neuropodia. Colour in ethanol white.

Prostomium simple (Fig. 16 B), trapezoid, slightly rounded, widest anteriorly; posterior prostomium with a pair of low, straight or slightly arched, transverse ridges, anteriorly wide, touching in midline and reaching to lateral prostomial margins. Colour of ridges in ethanol yellow. Lower lip laterally covering prostomium, without longitudinal folds. Nuchal organs along anterior margins of ridges (Fig. 17 A). Eyes absent. Buccal tentacles few in number, long, thick and smooth (Fig. 16 B), attached to upper lip from below, upper lip folded upwards. TS-2 with paleae, few in number (ca. 5), (Figs 16 B, 17B, 17C), only slightly longer than chaetae of TC-1; paleae directly below outermost branchial pair, more ventral than chaetae of subsequent notopodia, directed forward. Four pairs of branchiae, anterior pairs thicker than posterior pairs (Figs 16 A, 16C, 17B). Arrangement of branchiae in two distinct lateral groups, separated by distance smaller than diameter of innermost branchiophore. Within groups branchiae arranged in two rows with posterior branchiae directly behind anterior ones. Posterior outer branchiophore connected with notopodia of TC-3 (TS-5), those of second to last branchial pair connect with TC-2 (TS-4), anterior branchiophores originating from TS-2 and 3. Branchiae cirriform, smooth, anterior ones slightly wrinkled. Outermost pair about ½ to ½ the length of inner pairs.

15 TCs, first two anterior pairs of notopodia smaller than subsequent ones, chaetae as long as following ones. Chaetae all of same kind, simple capillaries, slightly limbate (Fig. 17 D) [partially retracted in some specimens]. 12 TUs, all neuropodia large tori; gradually decreasing in size towards posterior (Fig. 16 C, D); those of TU-1 twothree times larger than those of last TU. Large interramal papillae visible between notopodia and neuropodia of last two TUs, these similar in size to notopodia. [In larger specimens papillae fused to notopodia, increasing the appearance of the size of notopodia. Additionally, small interramal papillae in TC-2 to TC- 7 in some specimens (Fig. 17 E).] Notopodia of last two TCs shifted dorsally (Fig. 16 A, D), especially in 2nd to last TC. No further modifications and differences in posterior two TCs. [Uncini of thoracic neuropodia with dental formula about: MF- 3-3-3-∞.] 13 AUs [8–12], abdomen short, about 2/3 of thorax length. Neuropodia of AU-1 and AU-2 resembling tori of posterior TUs (Fig. 16 D), triangular in shape with minute uncini positioned on apical tip; remaining neuropodia erect pinnules as distinct folds with uncini positioned on outer margin of lobes. [Abdominal uncini with dental formula: MF-2-2-2-∞.] Rudimentary notopodia and neuropodial cirri absent. Distinct papillae dorsal to abdominal neuropodia [these fused to neuropodia in larger specimens forming pouches]. Pygidium lateral with lateral pair of long slim cirri (Fig. 16 A).

Nephridial papillae positioned dorsal to notopodia of TC-4 to TC-6 [sometimes also TC-3 to TC-8]. Methylene blue and green staining of ventral surface characterized by distinct ventral glandular shields separated by wide unstained bands from lower lip to last TU. Ventral shields of TS-2 to 5 with a fine unstained band.

Tubes transparent, membranous, covered with hemispherical fragments of foraminiferan shells (Fig. 17 F).

Remarks: The position of Noanelia within the Ampharetidea is uncertain due to the unusual attachment of buccal tentacles to the upper lip and the ventral glandular shields (Jirkov, 2011). The only other representative, N. hartmanae, was described from bathyal and abyssal depths of the Bay of Biscay in 1977 (Desbruyères & Laubier 1977) and Rejkjanes Ridge (Detinova 1985). The description of this species extends the distribution of the genus to deep southern hemisphere waters. Both species construct the very characteristic tube that is loosely covered by hemispherical foraminiferan shell fragments. Taking into account that Desbruyères and Laubier (1977) used a slightly different terminology (they considered the paleal segment as segment 3, while we consider it to be segment 2), the meristic characters of N. hartmanae and N. orensanzi n.sp. are very similar. Both species bear simple, capillary chaetae as paleae, followed by 15 true TCs. Thoracic uncini start in TC-4 and 12 TUs are present. Also, the number and general arrangement of branchiae, as well as the description of buccal tentacles match in the two species. Differences can be found in the number of AUs (12–15 in N. hartmanae, 8–13 in N. orensanzi n.sp.) and the dimension of branchiae. Naonelia hartmanae bears branchiae of four different sizes with the posterior pair only about 1/6 the length of the anterior pair (Desbruyères & Laubier 1977), these size differences are not as pronounced in N. orensanzi n.sp. The last two TCs are shifted dorsally in N. orensanzi n.sp., a feature not present in N. hartmanae. Also no information about interramal papillae is given by Desbruyères and Laubier (1977). The presence and position of nephridial papillae was hard to determine in N. orensanzi n.sp., however if apparent, they occurred in TS-6 to 8 (TC-4–6), in contrast to TS-4 to 6 as reported for N. hartmanae (Desbruyères & Laubier 1977, counted as TS-5 to 7 therein). In N. orensanzi n.sp. some intraspecific variability was observed between smaller and larger specimens. Some small specimens lacked chaetae in TS-2, and branchiae were arranged in a diamond shape as 1-2-1. Interramal papillae in thoracic and abdominal parapodia are clearly visible in small specimens, but are often fused to thoracic notopodial and abdominal neuropodial tori in large specimens.

Because of the differences of N. orensanzi n.sp. and N. hartmanae the generic diagnosis of the genus was emended. Noanelia orensanzi n.sp. does not display the large differences in size of the four branchial pairs, and also the dental formulas of the two species’ uncini differ from each other. As a consequence, branchial size and uncini dental formula were excluded from the generic diagnosis.

Etymology: The name was chosen to honour Prof. Dr. J. M. (Lobo) Orensanz who kindly provided the Ampharetidae from Patagonian waters described in this study.