Glyphanostomum holthei, 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 : 34-35

Glyphanostomum holthei sp. nov.

( Fig. 5 a–e)

Examined specimens. Holotype, So 110/1b, station 23 ROV, 57°26.631’N, 147°59.732’W to 57°27.316’N, 148°01.321’W, 4919–4947 m, 23.7.1996, 1 af ( SMF 17850). Paratypes, So 110/2, station 49 GBC, 54°18.056’N, 157°12.107’W, 4809 m, 8.8.1996, 2 af ( SMF 17846). Additional specimens: So 110/1b: Station 23 ROV, 57°26.631’N, 147°59.732’W to 57°27.316’N, 148°01.321’W, 4919–4947 m, 23.7.1996, 2 af ( SMF 17841). Station 24 TVG, 57°27.394’N, 148°00.013’W, 4743–4890 m, 24.7.1996, 2 af ( SMF 17842). Station 40 GBC, 54°18.17’N, 157°11.82’W, 4808 m, 2.8.1996, 38 af ( SMF 17844). Station 43 TVG, 54°18.196’N, 157°11.936’W, 4810 m, 3.8.1996, 2 af ( SMF 17848). So 110/2: Station 48 TVG, 54°18.064’N, 157°11.895’W, 4877 m, 8.8.1996, 11 af ( SMF 17845).

Description. Length of holotype (largest specimen) with 11 preserved abdominal segments ca. 30 mm; width (excl. parapodia) 2.2 mm. Holotype delicate and fragile. No complete specimen preserved, most of them broken in abdomen or posterior thorax. Body long and slender. Prostomium spade-shaped at anterior end, without eye-spots. Oral membrane extended, bearing ring of papillae ( Fig. 5 a, b). Buccal tentacles withdrawn, tips smooth. Three pairs of long and thin cirriform branchiae, arranged in transverse row on chaetiger 1 (segment III, Fig. 5 a, c). Median branchia of each group broken. Branchiae with fused bases. No median gap between left and right group of branchiae. Ventral side of segment II (prebranchial segment) with fleshy ridge, separating buccal area from thorax. Chaetae starting on segment III. Notopodia of first chaetiger reduced. Notopodia without cirri. Second unciniger with dorsal band between notopodia. Thoracic neuropodia free from body wall ventrally. Neuropodia of abdomen reduced to pinnules. Segmentation best visible on ventral side, indistinct on dorsal side. More than 11 abdominal segments. Pygidium unknown. Capillary chaetae appearing narrowly bilimbate in light microscope. Thoracic uncini with 2 vertical rows of four teeth each, single median tooth above these rows and one large median tooth between lower teeth of vertical rows ( Fig. 5 d); teeth of two rows shifted, resulting in alternate rows. Abdominal uncini with three vertical rows of four teeth each; uppermost tooth of median row delicate, and lowermost tooth of median row stronger than teeth of lateral vertical rows ( Fig. 5 e).

Remarks. In the subfamily Ampharetinae there are only two genera with three pairs of branchiae and 11 thoracic uncinigers, Ampharana Hartman, 1967 und Glyphanostomum . Due to its branchiae appearing to be arranged in a transverse row instead of a segmental arrangement the new species is placed in the genus Glyphanostomum . Of the three described species in this genus, G. pallescens , G. scotiarum Hartman, 1978 and G. abyssale Day, 1967 , the presence of papillae attached to an oral membrane (here: upper lip) has also been described for G. scotiarum . However, G. holthei sp. nov., is most similar to G. abyssale , especially in the shape of its prostomium and the branchiae inserted closely together in a transverse row. But G. a b y s s a l e differs from G. holthei sp. nov., in having a median gap between the pairs of branchiae, the lack of an oral membrane bearing papillae, the lack of the fleshy ventral ridge separating the buccal area from the thorax, and the presence of a pair of eye-spots. Additionally, G. abyssale is known only from abyssal waters near Cape Town, South Africa.

Etymology. This species is named after the outstanding polychaetologist and specialist of Terebellomorpha Torleif Holthe who passed away June 22, 2007 at the age of 61.

Distribution. North-East Pacific: Aleutian Trench.

Figures

FIGURE 5. Glyphanostomum holthei sp. nov. holotype (SMF 17850): a: lateral overview, b: anterior part with oral membrane extended (O = Oral membrane, P = Papillae, R = Ventral ridge), c: schematic drawing showing arrangement of branchiae, d: thoracic uncinus, frontal view, e: abdominal uncinus, frontal view.