Amage benhami, Reuscher, Michael, Fiege, Dieter & Wehe, Thomas, 2009

Reuscher, Michael, Fiege, Dieter & Wehe, Thomas, 2009, Four new species of Ampharetidae (Annelida: Polychaeta) from Pacific hot vents and cold seeps, with a key and synoptic table of characters for all genera, Zootaxa 2191, pp. 1-40 : 21-22

Amage benhami sp. nov.

( Fig. 1 a–g)

Amage sculpta — Benham 1927: 121 -123, Tab. III, figs. 94–99.

Specimens examined. Holotype, So 109/2, station 119 TVG, 44°40.146' N, 125°6.685' W, 625 m, 24.6.1996, 1 cs (SMF 17813). Additional specimens: Antarctic Terra Nova Expedition, Ross Sea: opposite of Granite Harbor, Station 340, 76°56’S, 164°12’E, 293 m, mud, 2 cs (BMNH 1928.2.29.2/3), det. Benham as Amage sculpta Ehlers, 1908 .

Description. Length of holotype 14 mm without anal cirri; width (excl. parapodia) 1.9 mm. Body almost broken in two parts between thorax and abdomen, held together by thin dermal ribbon on ventral side ( Fig. 1 a). Anterior part of body broad, tapering gradually from unciniger 7. Prostomium with two conspicuous anterolateral horns ( Fig. 1 b). No eye-spots. A pair of nuchal organs visible as oval fields framed by posterior U-shaped lobe ( Fig. 1 b). Buccal tentacles withdrawn but tip of one tentacle visible, without papillae. Four pairs of branchiae. Left and right group of branchiae widely separated. First two branchiae of each group in transverse row on segment III (chaetiger 1). Third and fourth pair of branchiae on chaetiger 2 in diagonal row with outer branchiae of transverse row ( Fig. 1 c). All branchiae broken off in holotype but number and arrangement visible as scars. First branchial segment protruding medially between branchiae. Chaetiger 2 (segment IV) divided dorsally into anterior and posterior part, each bearing one pair of branchiae ( Fig. 1 c). 15 thoracic chaetigers from segment III, chaetae of first chaetiger broken. Thoracic notopodia with conspicuous digitiform process ventral to chaetal fascicle. 12 thoracic uncinigers. Anterior thoracic tori long, gradually shortening towards posterior end with first thoracic tori about twice as long as posteriormost. Ventral part of tori free from body wall. 15 abdominal segments with conspicuous rudimentary notopodia with bluntly digitiform tips. Abdominal neuropodia with minute dorsal papilla. Left and right neuropodia of abdominal segments connected by transverse ventral ridge. Pygidium with one pair of lateral anal cirri, as long as last five abdominal segments. Notochaetae bilimbate. Thoracic uncini with five teeth above basal prow, arranged 1:1:2:1:prow ( Fig. 1 d, e). Abdominal uncini with numerous teeth in three non-parallel vertical rows ( Fig. 1 f, g).

Variation in other specimens examined. Length 11 mm and 21 mm, respectively. Several smooth tentacles visible, with smooth cirriform branchiae, in same arrangement as found in holotype, 16 abdominal segments.

Remarks. The species of the genus Amage currently described have 10, 11 or 14 thoracic uncinigers. Although Amage benhami sp. nov., has 12 thoracic uncinigers, there is no doubt about its generic affiliation because of the characteristic cirri of thoracic notopodia, abdominal rudimentary notopodia with digitiform tips and nuchal organs.

Benham (1927) studied two specimens of Amage from the Antarctic Terra Nova Expedition which he identified as Amage sculpta Ehlers, 1908 . The description provided by Benham, however, fits exactly to the specimen found in our sample from So 109/2, station 119 from off Oregon. Our re-evaluation of Benham’s specimens (BMNH 1928.2.29.2/3) revealed a number of differences between Amage sculpta as described by Ehlers (1908), and Benham’s and our specimens. Ehlers reported 14 pairs of notopodia and 11 thoracic uncinigers instead of 15 and 12, respectively, as present in A. benhami sp. nov. The prostomial shape of A. sculpta differs from the new species by the lack of the anterolateral horns. The anal cirri of A. sculpta are only present as small papillae, while A. benhami sp. nov. has long filiform appendages. Additionally, A. sculpta lacks the minute dorsal papillae of the abdominal neuropodia present in A. benhami sp. nov.

Etymology. The species is named after Sir William Blaxland Benham (1860–1950), who described specimens from the Antarctic Ross Sea in 1927 as belonging to Amage sculpta .

Distribution. North-East Pacific: Cascadia Margin off Oregon, USA. Antarctic: Ross Sea

Figures

FIGURE 1. Amage benhami sp. nov. holotype (SMF 17813): a: lateral overview, b: prostomium with two conspicuous anterolateral horns, c: schematic drawing showing arrangement of branchiae, d: thoracic uncinus, lateral view, e: thoracic uncinus, frontolateral view, f: abdominal uncinus, lateral view, g: abdominal uncinus, frontal view