Amage micropaleata, 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 : 210-212

Amage micropaleata n.sp.

Figs 3–5

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-26049].

Paratypes: ANDEEP I–II—st 42-2, EBS, 59°40.29'S – 59°40.32'S, 57°35.43'W – 57°35.64'W, Ona Basin/ Drake Passage, 3690 m (2 specimens, 1 x SEM, both 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 121-11, EBS, 63°38.27'S – 63°37.31'S, 50°37.16'W – 50°38.04'W, central Weddell Sea, 2668 m (1 specimen, 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 (1 specimen, complete) [ZMH-26050–26054].

Diagnosis: The species can be recognized by the presence of microscopic paleae.

Description: Holotype 5 mm long, 1 mm wide. Paratypes 4–6 mm long and 0.9–1.1 mm wide at most expanded part. Thorax anteriorly expanded, gradually tapering towards transition to abdomen, then abruptly tapering towards pygidium ( Fig. 3 A). Last three AUs expanded, giving the posterior end a cone-shaped appearance. Complete specimens with 7–9 AUs. Colour in ethanol white.

Prostomium trilobed ( Figs 3 B, 4A). Middle lobe with two distinct lateral horns. Anterior margins of lateral prostomial lobes, upper and lower lip expanded ( Fig. 3 C). Nuchal organs present in crest separating prostomial lobes ( Fig. 4 B). Buccal tentacles surface structure smooth ( Fig. 4 A). TS-1 apparent through dorsal and ventral rudimentary sutures. TS-2 with minute paleae and rudimentary papilliform notopodial lobe (fig. 4C). Paleae few in number, with a smooth surface ( Fig. 4 C) [often not apparent under low magnification]. Four pairs of branchiae originating from TS-2 to 5, last pair much smaller than first three ( Fig. 3 A–C). Branchiae arranged in two lateral groups, clearly separated from each other. 1st and 2nd pair situated on transverse line on anterior margin of TS-3, 3rd pair on TS-4, and 4th pair positioned between TS-4 and 5. Segmentation between branchiae clearly visible. Branchiostyles cirriform, densely covered with minute papillae, appearing smooth under low magnification. Branchiae with ventral longitudinal groove. 14 TCs starting in TS-3 with notopodia of first three anterior TCs well developed, but distinctly smaller than subsequent. Chaetae simple, stout and golden-coloured ( Fig. 4 D). Notopodial cirri absent. 11 TUs, starting in TS-6 (TC-4). All neuropodia large tori, gradually decreasing in length, neuropodia of TU-1 about twice as long as those of TU-11. [Anterior uncini to about TU-4/-5 with dental formula: MF-2-2-2-1 ( Fig. 5 A, B), posterior TUs with dental formula: MF-2-3-(3 to 5)-2 ( Fig. 5 C, D); lateral sides of uncini with numerous small teeth.] 9 AUs. Neuropodia and uncini of AU-1 somewhat intermediate in size between those of posterior TUs and AUs [dental formula: MF-(2 to 4)-3-3-(5 to ∞) ( Fig. 5 E)]. From AU-2 all neuropodia erect pinnules with marginal uncini [dental formula: MF-2 to 4-3-3-5 to ∞ ( Fig. 5 F)]. Neuropodial cirri absent. Segmentation of abdomen clearly visible, neuropodia ventrally connected by transverse ridges. Rudimentary notopodia on abdomen well-developed, elongate with blunt tips. Interramal papillae positioned somewhat anterior to parapodia in TUs and AUs. Papillae of TUs larger, oval in shape, those of AUs decreasing in size to minute spheres in posterior segments. Pygidium a terminal ring, with two short lateral cirri resembling elongated papillae ( Fig. 3 A).

Nephridial papillae present directly anterior to notopodia of TC-2 (TS-4).

Tube unknown.

Remarks: The new species is most similar to the type species A. auricula , and its subspecies Amage auricula sibogae Caullery, 1944 . The six specimens in the samples of the ANDEEP I–III expedition reveal a number of characters that distinguish A. micropaleata n.sp. from the aforementioned species and subspecies. The most outstanding character of A. micropaleata n.sp. is the presence of minute chaetae in TS-2 which are not described for either A. auricula or A. auricula sibogae . Thoracic notopodial cirri, formerly considered a generic character, are absent in A. micropaleata n.sp. Furthermore, the shape of abdominal uncini differs clearly from that of A. auricula (dental formula: MF-1-2-1-∞, personal observation by Jirkov (2001), non-type material). The holotype bears two short anal cirri resembling elongated papillae, while A. auricula bears a pair of anal papillae, and A. auricula sibogae lacks pygidial appendages. These cirri were not, however, observed in the paratypes and might be a character subject to intraspecific variation.

Etymology: The name refers to the presence of microscopic paleae as a unique feature in the genus.

Figures

FIGURE 3. Amage micropaleata n. sp. (A—holotype, ANDEEP III st. 133 - 2, ZMH- 26049); B and C—paratype, ANDEEP I – II st. 42 - 2, ZMH- 26050) A—habitus, lateral view, B—anterior end, dorsal view, C—anterior end, lateral view.

FIGURE 4. Amage micropaleata n. sp. (paratype, ANDEEP I – II st. 42 - 2, ZMH- 26051) SEM A—anterior region, B—nuchal organ, C—paleae, D—notochaetae TC- 1 (TS- 3).

FIGURE 5. Amage micropaleata n. sp. (paratype, ANDEEP I – II st. 42 - 2, ZMH- 26051) SEM (digitally traced from original) A—uncini of neuropodium of TU- 1, B—uncini of neuropodium of TU- 4, C—uncini of neuropodium of TU- 6, D—uncini of neuropodium of TU- 11, E—uncini of neuropodium of AU- 1, F—uncini of neuropodium of medium AU.