Kirkegaardia glabra, Blake, 2023

Blake, James A., 2023, New Species of Cirratulidae (Annelida) from Continental Slope and Abyssal Depths off Eastern Australia, Records of the Australian Museum (Rec. Aust. Mus.) 75 (3), pp. 249-270 : 265-266

Kirkegaardia glabra sp. nov.

urn:lsid:zoobank.org:act:98E70196-990D-4F3C-9407-C3FFEE9C7636

Figs 11–12

Holotype: Abyssal plain off eastern Australia, between Victoria and Tasmania , Flinders Marine Park, RV Investigator, Sta. 016, coll. 21 May 2017, Brenke sledge , 40.463°S 149.415°E to 40.461°S 149.364°E, 4131 m ( AM W.53527) . Paratype (1): Bass Strait Marine Park, Sta. 028, coll. 22 May 2017, Box core, 39.500°S 149.535°E, 4147 m (1, AM W.52707) .

Description. Holotype, incomplete, elongate, narrowbodied; with 23 setigers, 6.15 mm long and 0.48 mm wide across setiger 5. First eight setigers short, about three times wider than long; following segments becoming longer, about as wide as long; no segments rounded or moniliform. Ventral grooves and ridges absent. Parapodia of anterior setigers elevated above dorsal midline producing shallow mid-dorsal channel or groove; this channel with narrow elevated medial ridge or keel continuing to end of setiger 12, thereafter dorsal surface of individual segments rounded, with no groove or ridge. Paratype incomplete, with body distorted, twisted and stretched resulting in middle and posterior segments becoming elongate; with about 30 setigers, 13.6 mm long and 0.36 mm wide across thorax. Colour in alcohol opaque white with no pigment markings.

Pre-setiger region about three times as long as wide ( Figs 11A , 12A ); prostomium and peristomium merging dorsally, separated by mouth ventrally ( Fig. 11A ). Prostomium conical, tapering to narrow rounded tip; eyes absent; oval-shaped nuchal organs present on posterior lateral margins ( Fig. 11A ). Peristomium elongate, smooth without annulations, dorsal surface with paired longitudinal grooves producing low mid-dorsal crest from prostomium to anterior margin of setiger 1 ( Fig. 11A ). Dorsal tentacles arising on posterior margin of peristomium, with first pair of branchiae posterolateral to tentacles ( Fig. 11A ); second pair of branchiae on posterior margin of setiger one dorsal to notosetae and on edge of mid-dorsal channel; subsequent thoracic branchiae in similar location. Branchiae mostly absent, reduced to scars or stubs.

Parapodia reduced, with podial lobes of short anterior setigers rounded, inconspicuous; segments of longer segments; with no obvious podial lobes. Intersegmental grooves with glandular tissue retaining MG when applied (see below). Setae all denticulated capillaries with about 6–9 capillaries in anterior noto- and neuropodia and 5–6 in more posterior setigers. Capillaries with minute denticles along one edge ( Fig. 11B ), with details best observed at 1000× in light microscope, but visible at 400×; notosetae long, thin; neurosetae shorter, becoming more spinous than notosetae. Notosetae with denticles directed ventrally and denticles of neurosetae directed dorsally, and vis­à­vis.

Nature of posterior end and pygidium unknown.

Methyl Green staining. Methyl Green imparts a diagnostic staining pattern to this species ( Fig. 12A ). The prostomium and peristomium are relatively unstained; the anterior setigers retain a light stain on the anterior half of individual segments, this becoming intense on setigers 9–12, then entirely absent on following segments. All segments retain stain in the intersegmental grooves which produces bands surrounding the body in posterior segments ( Fig. 12A ).

Remarks. Kirkegaardia glabra sp. nov. although poorly represented, can be easily recognized by the long, narrow smooth peristomium that lacks annular rings but has a low, indistinct dorsal crest along its entire length. Other species having an elongate narrow peristomium entirely lacking annular rings are K. carinata Blake, 2016 from lower slope and abyssal depths off northern California and K. chilensis Blake, 2016 from slope and bathyal depths off Chile. Kirkegaardia glabra sp. nov. differs from both of these species in having instead of lacking a low dorsal crest or ridge along the peristomium. Both K. carinata and K. glabra sp. nov. have distinctive MG staining patterns. In K. carinata , however, the staining pattern is intense, and extends over the entire body from the peristomium to posterior segments, whereas in K. glabra sp. nov. the stain is absent on the pre-setiger region and weak or absent on anterior setigers, with only setigers 9–12 having an intense stain. In addition, while the intersegmental grooves retain stain along most of the body in K. glabra sp. nov., it is the parapodia themselves that retain the stain in K. carinata .

Etymology. The epithet is derived from the Latin, glaber, for smooth in reference to the smooth, uninterrupted pre-setiger region of this species.

Distribution. Abyssal plain between Tasmania and Victoria, eastern Australia, 4107–4147 m.

Figures

Figure 11. Kiregaardia glabra sp. nov. (A–B) holotype (AM W.53527). (A) anterior end, right lateral view; (B) denticulated capillary neurosetae from abdominal setiger, inset not to scale.

Figure 12. Kiregaardia glabra sp. nov. Photomicrograph of holotype (AM W.53527), anterior fragment, left lateral view showing distribution of MG stain after differentiation of stain. Arrows denote intersegmental concentrations of MG stain.