Amage septemdecima, 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 : 214-216

Amage septemdecima n.sp.

Figs 6–7

Holotype: Knipovich 248, 35°36‘S, 52°43‘W, 170 m [ZMH-26055].

Paratypes: Knipovich 260, 35°22.6‘S, 52°48.5‘W, 144 m (1 specimen, SEM, complete), Knipovich 1066, 34°29.2‘S, 52°20‘W, 72–86 m (1 specimen, complete) [ZMH-26056–26057].

Diagnosis: The species can be recognized by the number of thoracic chaetigers (17 TC, 14 TU)—which has only been described for A. adspersa —branchiae arranged as 3-1 without a gap between the two lateral branchial groups, and the absence of pygidial appendages.

Description: Holotype 9 mm long and 1.5 mm wide in broadest part, complete with 14 AUs ( Fig. 6 A). Paratypes 13–14 mm long and about 2 mm wide, with 13–15 AUs. Anterior half of thorax expanded, gradually tapering posteriorly. Abdominal segments distinctly narrower than thoracic ones, their length gradually decreasing towards pygidium. Colour in ethanol white.

Prostomium trilobed, lobes separated by deep folds ( Fig. 6 B). Middle lobe anteriorly broadened, without lateral horns. Posterior border of middle and lateral lobes orange-brownish in colour, laterally with two oval fields. Lower lip slightly enlarged, longitudinal folds indistinct ( Fig. 6 C). Nuchal organs not apparent [even under SEM ( Fig. 7 A)]. Buccal tentacles numerous, smooth. [TS-2 with small lateral lappets in some specimens] Spherical rudimentary notopodia without chaetae. Four pairs of branchiae originating from TS-2 to 5. Anterior three branchial pairs shifted to form almost straight transverse line without medial gap. Second innermost pair basally connected with notopodia of TS-4 (TC-2). Fourth branchial pair positioned behind second innermost pair, connected with notopodia of TS-5 (TC-3). Branchial surface smooth. 17 TCs, first three notopodial pairs close to each other, less developed than subsequent notopodia with first one the smallest. All chaetae stout and golden-coloured. Notopodial cirri absent. 14 TUs, neuropodia as welldeveloped tori, those of TU-1 largest, twice as large as neuropodia of last TU. [Uncini with main fang surmounted by 2 to 4 transverse rows of 2 to 1 teeth, number of transverse rows varying within neuropodia ( Fig. 7 B, C)]. 14 AUs, all erect pinnules with uncini positioned marginally [uncini of similar shape as thoracic ones with identical dental formula ( Fig. 7 D)]. Rudimentary notopodia and parapodial cirri absent. Pygidium without appendages ( Fig. 6 A).

Nephridial papillae not apparent. Tube unkown.

Remarks: Amage species are commonly characterized by low numbers of thoracic chaetigers (14TCs/11TUs, e.g., Fauchald 1977; Holthe 1986; Reuscher et al. 2009). Nevertheless, the presence of 17 TCs as found in A. septemdecima n.sp. has also been reported for Amage adspersa (Grube, 1863) and Reuscher et al. (2009) already included this high number of TCs in their emended diagnosis of the genus. Amage septemdecima n.sp. is characterized by a number of generic Amage traits which are the trilobed prostomium, presence of a pair of rudimentary notopodia without chaetae in TS-2, an expanded anterior region and abruptly narrowing abdomen, absence of thoracic-type abdominal neuropodia, stout and golden-coloured chaetae, and characteristic dental arrangement in thoracic uncini. Amage septemdecima n.sp. differs from all other species of Amage by the lack of abdominal rudimentary notopodia. Also, nuchal organs were not observed in specimens even under SEM. Unlike former descriptions of species of the genus (Reuscher et al. 2009; Hessle 1917) this species lacks thoracic notopodial cirri. Also, these were not observed for A. micropaleata n.sp. as well as for some specimens of Amage sculpta Ehlers, 1908 that were examined during this study, resulting in the exclusion of this character from the emended generic diagnosis presented herein.

Etymology: The name refers to the unusual number of thoracic chaetigers, with 17 TCs.

Figures

FIGURE 6. Amage septemdecima n. sp. (A—holotype, Knipovich 248, ZMH- 26055; B and C—paratype, Knipovich 1066, ZMH- 26056) A—habitus, lateral view, B—prostomium, frontal view, C—anterior end, ventro-lateral view.

FIGURE 7. Amage septemdecima n. sp. (paratype, Knipovich 260, ZMH- 26057) SEM A—prostomium, dorso-lateral view, arrows—proximal part of branchiae, B—neuropodium of median TU, C—uncini of neuropodium of median TU, D—uncini of neuropodium of anterior AU.