Anobothrus paleaodiscus, Schüller, Myriam & Jirkov, Igor A., 2013

Schüller, Myriam & Jirkov, Igor A., 2013, New Ampharetidae (Polychaeta) from the deep Southern Ocean and shallow Patagonian waters, Zootaxa 3692 (1), pp. 204-237 : 216-221

Anobothrus paleaodiscus n.sp.

Figs 8–9

Holotype: ANDEEP III—st 133-2, EBS, 62°46.73'S – 62°46.33'S, 53°02.57'W – 53°04.14'W, central Weddell Sea, 1582 m [ZMH-26058].

Paratypes: ANDEEP I–II—st 133-3, EBS, 65°20.15'S – 65°20.09'S, 54°14.35'W – 54°14.36'W, central Weddell Sea, 1123 m (1 specimen, incomplete), ANDEEP III—st 16-10, EBS, 41°07.55'S – 41°07.02'S, 09°55.94'E – 09°54.85'E, South Africa / South Atlantic, 4720 m (1 specimen, complete), st 74-6, EBS, 71°18.42'S – 71°18.33'S, 13°58.21'W – 13°57.65'W, eastern Weddell Sea, 1047 m (1 specimen, incomplete), 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 (5 specimens, 1 x SEM, 1 complete), st 133-2, EBS, 62°46.73'S – 62°46.33'S, 53°02.57'W – 53°04.14'W, central Weddell Sea, 1582 m (5 specimens, 1 complete) [ZMH-26059–26064].

Diagnosis: The species can foremost be recognized by its prominent, long paleae that originate from a disc-like epidermal structure, and the enlarged anterior neuropodia.

Description: Holotype 11 mm in long and 1.2 wide, with 2 AUs, incomplete. Paratypes 2–13 mm long and about 0.3–1.3 mm wide, with 12 AUs when complete ( Fig. 8 A). Colour in ethanol white.

Prostomium trilobed, middle lobe anteriorly rounded, without ridges ( Fig. 8 B). Lower lip not enlarged. Nuchal organs and eyes present. Buccal tentacles all retracted, surface structure unknown. TS-2 bearing>10 prominent paleae originating from an epidermal disc ( Figs 8 A, B). Paleae somewhat golden-coloured, long and stout at base with fine tips, arranged in an almost closed circle, anteriorly protruding the prostomium [sometimes meeting in midline]. Four pairs of branchiae ( Fig. 8 B). Anterior three pairs attached to each other across dorsum, arranged in an almost straight line forming a prominent ridge. Fourth pair attached only slightly posterior to second outermost pair, connected with notopodia of TC-3 (TS-5). Diameter of all branchiae more or less equal. Branchiae smooth. 15 TCs. TC-1 (TS-3) with notopodia distinctly less developed than subsequent ones, slightly displaced dorsally, with few short chaetae. Notopodia of TC-2 better developed, but still smaller than subsequent ones. Notopodia of last three TCs (TC-13 to -15) most developed with long, upright lobes. Median and posterior thoracic segments (TC-7 to -15, TU-4 to -12) slightly prolonged, not separated by clear suture, and notopodia connected by distinct lateral folds longitudinally. Notochaetae simple, narrowly limbate. 12 TUs, starting in TC-4 (TS-6). First two to three pairs of neuropodia about twice as long as remaining ones. Thoracic uncini numerous and small [dental formula with main fang surmounted by about 7–8 transverse rows of 3–4 teeth, surmounted by numerous small teeth ( Fig.

9A)]. Circular white band present in anterior half of TU-3 (TC-6, TS-8). Notopodia of 5th to last TC shifted slightly dorsally ( Fig. 8 A) and connected by a low dorsal ridge, notochaetae and uncini of shifted parapodia not modified. Neuropodia of AU-1 and AU-2 similar to thoracic ones, with uncini positioned in the middle of the sessile tori ( Fig. 9 B). [12 AUs, distinct from AU-3, prolonged erect pinnules with uncini in marginal position. Abdominal uncini with dental formula with a main fang surmounted by two transverse rows of about 5 teeth, surmounted by numerous small teeth. Rudimentary abdominal notopodia absent.] All thoracic and abdominal noto- and neuropodia without cirri. Pygidium without appendages.

A pair of nephridial papillae positioned directly posterior to branchial ridge in TC-3 ( Fig. 8 B).

Tube unknown.

Remarks: Most specimens are incomplete, with only three specimens of comparably small size complete. In these specimens, however, the distinguishing characters of the species are not as prominent as in larger specimens. Hence, a large but incomplete specimen in good condition is chosen as holotype to display all important characters for species recognition. The most apparent and prominent character to distinguish species of Anobothrus from each other is development of the paleae. While in Anobothrus apaleatus Reuscher, Fiege and Wehe, 2009 they are reduced, all other species of the genus bear more or less well developed paleae in TS-2. Anobothrus paleaodiscus n.sp. bears very conspicuous paleae that are very stout and long enough to cross in front of the prostomium in some specimens. Paleae of similar length are only known for Anobothrus glandularis (Hartmann-Schröder, 1965) , a species also found in the ANDEEP I–III material and most similar to A. paleaodiscus n.sp. However, the paleae in A. paleaodiscus n.sp. originate from a distinct disc-like structure as opposed to the paleae of A. glandularis which originate directly from the body wall. Such a disc-like structure is also described for Anobothrus wakatakamaruae Imajima, 2009 as a large cylindrical lobe from which 24–25 palae arise. A detailed list on distinguishing characters of the Southern Ocean Anobothrus species is presented in Table 3 .

Etymology: The paleae of the species emerge from a somewhat disc-shaped membranous lobe and are arranged in a circle around its margin.

species further notes Abderos minotaurus gen.nov. n.sp. forwardly directed lateral papillae on TS-1

Amage sculpta

Amage septemdecima n.sp.

Amage micropaleata n.sp.

Anobothrus antarctica paleae gradually tapering, median length

Anobothrus apaleatus paleae absent

Anobothrus glandularis paleae very well developed, long Anobothrus paleaodiscus n.sp. paleae long and stout, on a membranous disc Anobothrus patagonicus paleae smaller than most developed chaetae, short Anobothrus pseudoampharete paleae stout, tapering abruptly, median length, in a wide fan Anobothrus rubropaleatus n.sp. paleae well developed, abrubtly tapering, reddish, medium length Anobothrus wilhelmi n.sp. paleae fine, often folded and directed dorsally, median length Noanelia orensanzi n.sp.

Zatsepinia antarctica n.sp.

explanation of number codes:

Figures

FIGURE 8. Anobothrus paleaodiscus n. sp. (paratype, ANDEEP III st. 133 - 2, ZMH- 26064) A—habitus lateral view, Banterior end, dorsal view.

FIGURE 9. Anobothrus paleaodiscus n. sp. (paratype, ANDEEP III st. 81 - 8, ZMH- 26063) SEM (original and digitally traced) A—uncini of neuropodium of TU- 1 (inner four traced in detail, outer pairs outlined schematically), B—neuropodium of AU- 1.

Tables

TABLE 3. Morphological traits of all species described herein, as well as congeneric ampharetid species reported for the Southern Ocean (T-AU—AUs with thoracic shape, notop. — notopodia / l, neurop. — neuropodia / l, branchial arrangement: number of branchial pairs in first, second, third and forth row from anterior)

species prostomium	lower lip	buccal tentacles	rudimentary palea notop. in TS-2
Abderos minotaurus gen.nov. n.sp. trilobed	1	0/2	0 0
Amage sculpta Ehlers, 1908 trilobed	1	2	0 1
Amage septemdecima n.sp. trilobed	1/2	0	0 1
trilobed with Amage micropaleata n.sp. lateral horns	1	0	1
Anobothrus antarctica (Monro, 1939) trilobed	1	2	1
Anobothrus apaleatus Reuscher et al. , trilobed 2009	1	2	0 0
Anobothrus glandularis (Hartmann- Schröder, 1965) trilobed	1	0	1
Anobothrus paleaodiscus n.sp. trilobed	1	0	1
Anobothrus patagonicus (Kinberg, 1866) trilobed	1	0	1
Anobothrus pseudoampharete Schüller , weakly 2008 trilobed	1	0	1
Anobothrus rubropaleatus n.sp. trilobed	1	?	1
Anobothrus wilhelmi n.sp. trilobed	1	0	1
Noanelia orensanzi n.sp. simple	1	0	1
Zatsepinia antarctica n.sp. simple	1	0/1	0 0
0		smooth	absent absent
explanation of number codes:1	simple	longitudinal grooves	present present
2	transverse folds	papillated