Pseudomystides Bergström, 1914

Georgieva, Magdalena N., Wiklund, Helena, Ramos, Dino A., Neal, Lenka, Glasby, Christopher J. & Gunton, Laetitia M., 2023, The Annelid Community of a Natural Deep-sea Whale Fall off Eastern Australia, Records of the Australian Museum (Rec. Aust. Mus.) 75 (3), pp. 167-213 : 199

Pseudomystides Bergström, 1914

? Pseudomystides sp.

Fig. 23

Material examined. NHMUKANEA 2022.409 – 411 , NHMUKANEA 2022.441 , IN2017 _ V03 _100; 9 June 2017; off Byron Bay , NSW, Australia, beam trawl, start: 28.05°S 154.08°E, 999 m, end: 28.10°S 154.08°E, 1013 m .

Description. Complete specimens 0.75–1.67 mm long with 11–14 segments ( Fig. 23A ). Segments of equal widths (0.13–0.27 mm) along length of body.

Prostomium wider than long and terminally cleft ( Fig. 23B ). Prostomium sometimes more darkly pigmented than rest of body. Terminal protuberance present where paired antennae and palps inserted. Frontal antennae and palps digitiform, both approximately same length as prostomium. Median antenna smaller and thinner than paired antenna and inserted near center of prostomium. Eyes absent. Proboscis retracted in all specimens.

Firstand secondsegmentsappearing fused, withfirstpairof tentacularcirriinsertedventralto prostomium. Threetentacular cirriwith broadbases taperingto apointedtip (1 + C1/1 + C0/ N). Cirri on segment 1 reaching segments 2–3, dorsal cirri on segment 2 reaching segments 4–5, ventral cirri on segment 2 reaching segment 4. No dorsal cirri present on segment 3.

Dorsal cirri present from segment 4, ventral cirrus from segment 3. Dorsal cirrus lanceolate, around 2× longer than wide, typically directed posterolaterally. Ventral cirrus lanceolate to digitiform, around 4× longer than wide. Both structures similar in size to parapodial lobe. Uniramous parapodia with compound spinigers having blades slightly shorter than shaft ( Fig. 23C ).

Pygidiumbroad and blunt with twotear-drop-shaped anal cirri ( Fig. 23D ). Median pygidial papilla present.

Distribution. IN2017_V03, Station 100. Pilot whale carcass, off Byron Bay, New South Wales, Australia in 999–1013 m.

Remarks. Phyllodocid genera that have three tentacular cirri in the first two segments and the third segment lacking a dorsal cirrusinclude Hesionura Hartmann-Schröder, 1958 , Mystides Théel, 1879 , and Pseudomystides Bergström, 1914 ( Eklöf et al., 2007). Hesionura and Mystides both have a pair of antennae and palps, fewer than the IN2017_V03 specimens. We assign these specimens to Pseudomystides since an additional median antenna is described in three of the fivedescribed species. Within the genus Pseudomystides , these differ from the other species in having far fewer segments, a broad prostomium, unlike Pseudomystides limbata ( Saint-Joseph, 1888) and Pseudomystides rarica ( Uschakov, 1958) , and digitiform to lanceolate dorsal and ventral cirri, unlike Pseudomystides bathysiphonicola ( Hartmann-Schröder, 1983) , Pseudomystides brevicirra Böggemann, 2009 , and Pseudomystides spinachia Petersen & Pleijel in Pleijel, 1993. The median antenna for the Australian specimens is also inserted near the middle of the prostomium, unlike in P. limbata , P. rarica , and P. spinachia where it is inserted posteriorly. We were unable to obtain DNA sequence data from the samples which prevented us from comparing their relationships with other Pseudomystides species.

Figures

Figure 23.?Pseudomystides sp., specimen NHMUKANEA 2022.409–411. (A) Photo of an ethanol-preserved specimen, scale bar is 200 µm; (B) light micrograph of prostomium and tentacular cirri of the first segment, scale bar is 75 µm; (C) light micrograph of compound spinigers, scale bar is 25 µm; (D) light micrograph of pygidium with anal cirri and papilla (arrow), scale bar is 100 µm.