Pseudoscalibregma glandipodium, Blake, 2023

Blake, James A., 2023, New Species of Scalibregmatidae (Annelida) from Slope and Abyssal Depths off Eastern Australia, Records of the Australian Museum (Rec. Aust. Mus.) 75 (3), pp. 271-298 : 293-296

Pseudoscalibregma glandipodium sp. nov.

urn:lsid:zoobank.org:act:7CEA87F9-0A79-417F-9C2F-E67A0971D2CA

Figs 13–14

Holotype: Eastern Australia, abyssal plain off New South Wales, Jervis Marine Park, RV Investigator, Sta. 054, coll. 28 May 2017, Brenke Sled , distance 2.6 km, 35.117°S 151.473°E, 4026 m to 35.099°S 151.455°E, 3881 m ( AM W.52697) . Paratypes (5): continental slope off New South Wales, Hunter Marine Park, Sta. 076, coll. 03 Jun 2017, Brenke Sled, distance 4.2 km, 32.577°S 153.161°E, 2534 m to 32.613°S 153.149°E, 2480 m (1, W.52350) ;— Continental slope off Tasmania, Freycinet Marine Park, Sta. 005, 18 May 2017, Brenke Sled, distance 2.8 km, 41.730°S 149.135°E, 2789 to 41.753°S 149.147°E, 2779 m (2, W.52679) ;— Sta. 011, coll. 19 May 2017, box core, 41.721°S 149.125°E, 2793 m (2, W.52682). All in Australian Museum .

Description. A small to moderate sized species, holotype complete with 31 setigers, 13 mm long, 3.4 mm wide across expanded anterior body and 0.8 mm wide across narrow posterior segments ( Fig. 13A ). Paratypes smaller, one from Sta. 011 (AM W.52682) with 26 setigers, 3.6 mm long, 0.95 mm across anterior setigers and 0.5 mm across posterior setigers. Body enlarged anteriorly, tapering posteriorly to narrow pygidial segment ( Fig. 13A ). Individual segments mostly biannulate, with prominent transverse ridge connecting right and left parapodia both dorsally and ventrally; second narrow ridge present anterior to parapodial ridge producing biannulate segments; segments separated by intersegmental groove, best seen in posterior segments; segmentation largely obscured on enlarged anterior segments. Segments not noticeably divided into rows of elevated pads as in most other scalibregmatids. Ventral surface of expanded anterior segments with subdermal longitudinal bands, probably muscles extending from peristomium to beginning of narrow posterior segments ( Figs 13C , 14B ). Dorsal and ventral grooves or ridges absent; posterior segments with narrow ventral line, probably nerve cord. Branchiae absent. Colour in alcohol opaque white; without body pigment.

Prostomium entire across anterior margin, bearing two narrow diverging frontal horns ( Figs 13A–C , 14A, B ); eyes absent; nuchal organs observed as a pair of swollen lobes on paratypes, relatively smooth ( Fig. 14A ); curved grooves on holotype. Peristomium a single ring dorsally; ventrally forming upper and lower lips of mouth; each lip with 6–7 short lobes ( Fig. 14B ); proboscis partially everted on two paratypes ( AM W.52682).

Parapodia of anterior setigers relatively inconspicuous with short conical lobes and noto- and neuropodia well separated. Parapodia of posterior setigers becoming longer, bearing elevated inflated dorsal and ventral cirri ( Fig. 13D ); each cirrus irregularly shaped, lumpy, bearing large internal glands ( Fig. 13D–E ); interramal papillae absent.

Setigers 1–3 with capillaries arranged in 3–4 rows in both noto- and neuropodia of holotype, 2–3 rows on smaller paratypes, each successive row with longer setae; spinous setae not present on any specimens. Furcate setae from setiger 2 continuing on noto- and neuropodia on all setigers, these numbering 2–4 on anterior setigers, increasing to 9–10 per podium on posterior setigers of holotype; only 3–4 on smaller paratypes. Furcate setae present in first row followed by longer capillaries in subsequent row; each furcate seta with a pair of long tapering unequal tynes ( Figs 13F , 14C ) with minute denticles along inner borders of tynes ( Fig. 14C ).

Pygidium a simple lobe surrounding anus; holotype with one anal cirrus, subsequently lost; one paratype with anal two cirri; based on other species of this genus, this species likely with at least four anal cirri.

Remarks. Pseudoscalibregma glandipodium sp. nov. is most similar to P. bransfieldium ( Hartman, 1967) from continental slope depths of Antarctic seas in having dorsal and ventral cirri appearing as bulbous glandular extensions of the podial lobes. The two species differ in that P. glandipodium sp. nov. has no interramal cirrus between the noto- and neuropodia and no short acicular spines in the first few setigers, whereas P. bransfieldium has both of these characters. In addition, P. bransfieldium is reported to have a ventral groove along the body ( Blake, 2015), whereas P. glandipodium sp. nov. has a relatively smooth ventral surface. Ecologically, P. glandipodium sp. nov. is a lower slope and abyssal species reaching depths of 4000 m. In contrast, P. bransfieldium is an Antarctic shelf and upper slope species reaching depths of only about 900 m ( Blake, 2015).

Etymology. The epithet is from the Latin glandis, for glandular, and podium, for a foot-like structure in reference to the glandular nature of the parapodia of this species.

Distribution. Eastern Australia, off Tasmania and New South Wales; lower continental slope and abyssal depths, 2480–4026 m.

Figures

Figure 13. Pseudoscalibregma glandipodium sp. nov. Holotype (AM W.52697): (A) entire worm, dorsal view; (B) anterior end, dorsal view; (C) anterior end, ventral view; (D) posterior parapodium anterior view; (E) detail of dorsal cirrus from posterior parapodium, arrows indicate internal gland cells; (F) furcate seta. All stained with Shirlastain A.

Figure 14. Pseudoscalibregma glandipodium sp. nov. (A) anterior end dorsal view; (B) anterior end, ventral view; (C) furcate seta. A, paratype (AM W.52682); B, C, holotype (AM W.52697).