Chaetocirratulus pinguis Hartman, 1978

Blake, James A., 2018, Bitentaculate Cirratulidae (Annelida, Polychaeta) collected chiefly during cruises of the R / V Anton Bruun, USNS Eltanin, USCG Glacier, R / V Hero, RVIB Nathaniel B. Palmer, and R / V Polarstern from the Southern Ocean, Antarctica, and off Western South America, Zootaxa 4537 (1), pp. 1-130 : 68-69

Chaetocirratulus pinguis Hartman, 1978 , new combination

Figure 36

Chaetozone pinguis Hartman, 1978:166 , fig. 18a–c; Usha et al. 2014: 917.

Cirratulus patagonicus: Hartman 1978: 166 . Not Kinberg 1866.

Material examined. Weddell Sea, USCG Glacier Sta. 69-1, 24 Feb. 1969 , 74°28.1ʹS, 30°31.7ʹW, 513 m, holotype ( USNM 46782 ) and 13 paratypes ( USNM 46783 ); Sta. 68-5, 9 Feb 1968 , 76°00ʹS, 55°00ʹW, 400 (1, USNM 46800 ); Sta. 69-7, coll. 01 March 1969 , 77°16ʹS, 42°38ʹW, 512 m, (1, USNM 490733 ); Weddell Sea, east of former Larsen Ice Shelf A Area , RVIB Nathaniel B. Palmer Cr. 2000-03, coll. J.A. Blake, Sta. 26, 23 May 2000. 64°39.564ʹS, 059°13.226ʹW, SM grab, 564 m (1, MCZ 149836 ).— East Antarctic Peninsula, Prince Gustav Channel , RVIB Nathaniel B. Palmer Cr. 2000-03, coll. J.A. Blake , SM grab, Sta. 01, 14 May 2000 , 64°17.625´S, 058°34.678´W. 768 m (1, JAB); Sta. 34, 24 May 2000 , 64°10.995ʹS, 058°34.140ʹW, 865 m (5, MCZ 149837 ; 1 SEM stub, JAB); N of Larsen Ice Shelf Area A, off Lindenberg Island , RVIB Nathaniel B. Palmer Cr. 2000-03, coll. J.A. Blake , SM grab, Sta. 03, 15 May 2000 , 64°53.533ʹS, 059°30.694ʹW, 385m (1, MCZ 149838 ); former Ice Shelf A Area, Greenpeace Trough , RVIB Nathaniel B. Palmer Cr. 2000-03, coll. J.A. Blake , SM grab, Sta. 22, 20 May 2000 , 64°46.632ʹS, 060°21.557ʹW, 868 m (1, LACM-AHF Poly 10214); Sta. 12, 19 May 2000 , 64°55.101ʹS, 060°24.459ʹW, 317 m (1, LACM-AHF Poly 10215); former Ice Shelf A Area, border with Larsen B , RVIB Nathaniel B. Palmer Cr. 2000-03, coll. J.A. Blake , SM grab, Sta. 13, 19 May 2000 , 64°53.517ʹS, 060°28.836ʹW, 323 m (1, LACM-AHF Poly 10216); Sta. 14, 19 May 2000 , 64°51.818ʹS, 060°33.438ʹW, 419 m (4, LACM-AHF Poly 10217).— South Shetland Islands, Clarence Island , USNS Eltanin, Cr. 12, Sta. 1089, 17 Apr 64, 60.78°S, 53.507°W, Blake trawl, 641 m (1, USNM 1013943 ).— Ross Sea, Pennell Bank, off Ross Ice shelf, ca. 385 km W of McMurdo Station , USNS Eltanin Cr. 32, Sta. 2060, 25 Jan 1968 , 77.98°S, 178.18°E, Camera grab, 647 m (1, USNM 1490734 ) .

Description. A small species, specimen from USNS Eltanin Sta. 1089 (USNM 1013943) 6 mm long and 5.2 mm wide for 48 setigerous segments; types smaller, up to 4.2 mm long for 30 segments. Body distinctly fusiform in shape in types ( Fig 36A ) and some non-types; juveniles more elongate, thick, tapering posteriorly, thickened in middle, but not distinctly fusiform. Individual segments biannulate ( Fig. 36B ). Shallow mid-dorsal groove apparent in some specimens ( Fig. 36A ). Color tan, with no additional pigmentation.

Prostomium broadly rounded on anterior margin, subtriangular in shape, wider than long ( Fig. 36 A–B). Peristomium well developed, dorsally overlapping first segment somewhat, with deep lateral grooves forming

three weakly developed annular rings, well developed laterally ( Fig. 36B ); dorsum of peristomium relatively smooth, without dorsal crest ( Fig. 36A ). Dorsal tentacles medial in location, arising from groove between peristomium and setiger 1 ( Fig. 36 A–B) or anterior margin of first setiger; tentacles thick, short in preservation. First pair of branchiae arising lateral to dorsal tentacles in same groove between peristomium and setiger 1 ( Fig. 36 A–B); subsequent branchiae arising dorsal to setal fascicles ( Fig. 36B ), continuing through first half of body.

Capillary setae in noto- and neuropodia throughout; acicular spines in notopodia from middle and posterior setigers and in neuropodia from setiger 1–5. Acicular spines short, straight ( Fig. 36 D–E); capillaries sometimes with finely serrated or fringed border ( Fig. 36E , inset).

Pygidium terminating a conical lobe ventral to anal opening ( Fig. 36A ).

Methyl Green stain. The prostomium stains lightly; the peristomium stains heavily, especially on the sides; the body segments are generally unstained.

Remarks. Chaetocirratulus pinguis is similar to C. andersenensis in that most specimens have a robust, fusiform body. The two species differ in that the first has acicular spines present in the neuropodia from anterior setigers 1–5 instead of a far posterior setiger. Chaetocirratulus andersenensis has acicular spines limited to a few posterior neuropodia, rarely in notopodia; whereas in A. pinguis , acicular spines are present in both noto- and neuropodia throughout. In addition, the three peristomial rings are typically prominent and well-defined in C. andersenensis , but only weakly developed in C. pinguis , giving the pre-setigerous region a smooth appearance.

Habitat. Chaetocirratulus pinguis was noticeably abundant in the vicinity of the former Larsen Ice Shelf A where the surficial sediments (0–5 cm) consist of 0–40% sand likely derived from the formerly overlying ice cover ( Gilbert & Domack 2003).

Distribution. Weddell Sea and Antarctic Peninsula in shelf and upper slope depths, 317–865 m; East Antarctica, 203 m.

Figures

FIGURE 36. Chaetocirratulus pinguis (Hartman, 1978). A, entire worm, dorsal view; B, SEM of anterior end, dorsolateral view; C, SEM of anterior neurosetae; D, neuropodial acicular spine; E, neuropodial capillaries and spine (inset not to scale). A, D–E, paratype (USNM 46783); B–C, NBP Sta. 34, SEMs.