Anobothrus apaleatus, 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 : 28-29

Anobothrus apaleatus sp. nov.

( Fig. 4 a–e; Table 5)

Examined specimens. Holotype, So 157, station 33 TVG, 37°46.555’S, 110°54.615’W to 37°46.558’S, 110°54.635’W, 2206-2219 m, 29.6.2001, 1 cs ( SMF 17752). Additional specimens: So 110/1a: Station 9 TVG, 44°40.167’N, 125°05.855’W, 596 m, 12.7.1996, 1 cs ( SMF 17814). Station 11 TVG, 44°40.134’N, 125°06.503’W, 524 m, 12.7.1996, 1 cs ( SMF 17809). Station 15 ROV, 44°40.14’N, 125°05.72’W to 44°40.15’N, 125°05.81’W, 12.7.1996, 1 cs ( SMF 17811). Station 18 TVG, 44°34.235’N, 125°08.891’W, 778 m, 12.7.1996, 4 af ( SMF 17815), 1 af ( SMF 17816).

Additional type material examined: Sosanides glandularis Hartmann-Schröder, 1965 . Holotype, station 76, 73°39’W 38°16’S, 66 m, 11.3.1960, 1 cs ( ZMH P- 15029).

Description. Length of holotype 11 mm; width (excl. parapodia) 0.6 mm. Body narrow, gradually tapering towards pygidium ( Fig. 4 a). Prostomium trilobed, without eye-spots. Buccal tentacles withdrawn, tips densely covered with short papillae. Four pairs of long, narrow, cirriform branchiae on segment II. No gap between groups of branchiae. Three branchiae of each group arranged in a transverse line; one pair of branchiae slightly shifted backwards between innermost and outer two branchiae of each group ( Fig. 4 b). Paired nephridial papillae not visible. 15 thoracic chaetigers. First three notopodia reduced. First chaetiger with only one or two chaetae on each side, hardly visible. 12 thoracic uncinigers. Second unciniger anteriorly with circular glandular band. Fifth-to-last pair of notopodia elevated and connected by prominent dorsal glandular ridge. Elevated notopodia without morphological modifications, resembling remaining notopodia. Notopodia without cirri. Neuropodia from third abdominal segment onwards elongated pinnules. 12 abdominal segments. Abdomen long, encompassing about half of body length. Pygidium with terminal anus, surrounded by two lateral papillae and three minute dorsal papillae ( Fig. 4 c). Capillary chaetae appearing bilimbate under the light microscope. Chaetae of unciniger with elevated notopodia without visible modifications. Thoracic uncini with three vertical rows of four teeth each. Median row of teeth shifted, resulting in alternate rows. ( Fig. 4 d, e). Abdominal uncini similar to thoracic ones. Tube made of red deep-sea clay.

Variation. Other complete specimens (SMF 17809, SMF 17814, SMF 17811) 4–6 mm long. Dorsal ridge across unciniger 8 in other specimens less pronounced than in holotype.

Remarks. Anobothrus apaleatus sp. nov., differs from all other species of the genus Anobothrus by the lack of chaetae on segment II. But the presence of the elevated notopodia of unciniger 8 and the circular band on uncinger 2 clearly distinguish this species as belonging to Anobothrus . A synoptic overview of important characters for all valid species of the genus is given in Table 5.

The only other species with the circular band on unciniger 2 is Anobothrus laubieri ( Desbruyères, 1978) . This species can be easily distinguished by the possession of three instead of four pairs of branchiae. Anobothrus antarcticus Monro, 1939 is the only other species with papillose tentacles within the genus but has pronounced chaetae on segment II (paleae) and its circular band is situated on unciniger 3.

Type material of Anobothrus glandularis ( Hartmann-Schröder, 1965) , described as Sosanides glandularis , was examined to assess the synonymy of Anobothrus and Sosanides as suggested by Jirkov (2001). We follow Jirkov in considering the monotypic genus Sosanides Hartmann-Schröder, 1965 as a junior synonym of Anobothrus .

Detailed information for all genera considered valid and showing a dorsal modification are given in Table 6.

Etymology. The species is named for the lack of chaetae on segment II (paleae).

Distribution. North-East Pacific: Cascadia Margin (off Oregon, USA). South-East Pacific: Pacific- Antarctic Ridge.

Figures

FIGURE 4. Anobothrus apaleatus sp. nov. holotype (SMF 17752): a: lateral overview, b: schematic drawing showing arrangement of branchiae, c: pygidium, dorsal view, d: thoracic uncinus, lateral view, e: thoracic uncinus, frontal view. Elevated notopodia not apparent.