Orbiniella sp.

Meca, Miguel A., Kongsrud, Jon Anders, Kongshavn, Katrine, Alvestad, Tom, Meißner, Karin & Budaeva, Nataliya, 2024, Diversity of Orbiniella (Orbiniidae, Annelida) in the North Atlantic and the Arctic, ZooKeys 1205, pp. 51-88 : 51-88

Orbiniella sp.

Figs 14 , 15 , 16

Orbiniella petersenae : Parapar et al. 2015: 333–343, figs 3–9 (in part).

Clade.

Deep 4.

Material examined.

ZMBN 130943 (1 spm) ; ZMBN 157696 (1 spm on SEM stub) ; ZMBN 157665 (5 spms) ; ZMBN 157666 (2 spms on SEM stub) ; ZMBN 157667 (1 spm on SEM stub, DNA voucher Orbi 47) . 16 specimens from the O. petersenae sensu lato type series: IINH 43198 (5 spms) . IINH 43231 (11 spms) .

Description of ethanol preserved specimens.

DNA voucher Orbi 47 ( ZMBN 157667 ) incomplete with 15 chaetigers, 1.7 mm long and 0.3 mm wide at level of chaetiger 6. Body short and thick, with uniform width. Two more specimens from the same sample as the DNA voucher ( ZMBN 130943 and ZMBN 157696 ) in poor condition (i. e., anterior fragments of fewer than ten segments and destroyed chaetae). Pigmentation lacking in all analysed specimens.

Prostomium broad with rounded anterior margin, without eyespots (Fig. 14 A ). SEM micrographs showed no cilia on prostomium. Peristomium with two prominent achaetous segments, first segment shorter than second segment, distinctly separated from each other and first chaetiger by narrow annulus (Fig. 14 B ). Segmental annulation consisted of two narrow annuli between parapodia from parapodium 1 until end of available fragment (Fig. 14 A ). Posterior part and pygidium not observed.

Parapodia biramous, triangular-like, of similar size throughout fragment. Posterior notopodial lobes from chaetiger 1, digitate, short, and thick (Fig. 14 C ). Posterior neuropodial lobes absent. Crenulated capillary chaetae and acicular spines in both rami from chaetiger 1. Capillaries in anterior segments longer than body width and numerous (7–10 per bundle), shorter and reduced in number in posterior segments. Acicular spines short, stout, and smooth, up to three per ramus (Fig. 14 C, D ).

Description of formalin preserved specimens.

Five well preserved specimens originally fixed in formalin collected in the Norwegian Sea ( ZMBN 157665 ) as well as 16 specimens from O. petersenae sensu lato type series from the Iceland Sea shared similar morphology with the DNA voucher from Deep 4 clade (i. e., same segmental annulation pattern and chaetal distribution type). A morphological description of these specimens is provided below, although the affinity of them to Deep 4 clade remains unconfirmed with molecular data.

Shape of prostomium varies between broad and elongate, with rounded anterior margin (Fig. 15 A ). Eyespots absent. Peristomium with two prominent achaetous segments, first segment shorter than second segment, distinctly separated from each other and first chaetiger by narrow annulus.

Segmental annulation pattern as follows: two narrow annuli between parapodia from parapodium 1 until posterior body and three narrow annuli between parapodia in posterior-most body (Fig. 15 A, B ). Annulation well defined in pre-pygidial region (Fig. 15 C ). From chaetiger 7–10 onwards segments becoming longer, more square-shaped.

Parapodia biramous, triangular-like, of similar size throughout body. Postchaetal notopodial lobes from chaetiger 1, digitate, short, and thick (Fig. 14 C, E ). Postchaetal neuropodial lobes absent. Crenulated capillary chaetae and acicular spines in both rami from chaetiger 1. Notopodia and neuropodia bearing each 7–10 long crenulated capillaries, being longer than body width in anterior segments and shorter and less numerous in posterior segments. Capillary chaetae with crenulation occurring on one side along whole chaeta or along half of its length (Fig. 14 E ). Last five or six posterior segments slightly shorter and last two achaetous (Fig. 15 C ). Pygidium with four long and wide anal lobes (Fig. 15 D ).

Distribution.

Northern Greenland Sea, 3356 m. Possibly Iceland Sea and Norwegian Sea, 1844–2525 m (Fig. 16 ).

Figures

Figure 14. Orbiniella sp. SEM A specimen ZMBN 157696, anterior end, ventral view B specimen ZMBN 157696, detail of prostomium and peristomium C specimen ZMBN 157667, notopodium of chaetiger 6 showing notopodial lobe, acicular spine, and capillaries D specimen ZMBN 157696 Neuropodium of chaetiger 10 showing acicular spines E specimen ZMBN 157666, notopodia of chaetigers 5 and 6 showing notopodial lobe, acicular spines, and capillaries F specimen ZMBN 157666, detail of capillary chaetae. White arrows in E: Start of crenulation in capillary chaeta. Abbreviations: Ac: acicular spines; Np: notopodial lobe. Scales: 100 μm (A, B, E); 20 μm (C, D); 10 μm (F).

Figure 15. Orbiniella sp. SEM of ZMBN 157666 A anterior end, ventral view showing narrow annuli between parapodia 1 and 8 B midbody and posterior end, ventral view showing narrow annuli between parapodia 9 and 29 C posterior end, dorsal view D Detail of pygidium (insert of C). Numbers indicate narrow annuli between parapodia. Abbreviation: Par 1: first parapodium. Scale bars: 500 μm (A); 1000 μm (B); 200 μm (C); 100 μm (D).

Figure 16. Distribution of Orbiniella sp. Black lines – Greenland-Scotland Ridge (GSR), coloured square – station with examined morphology and molecular data, white squares – stations with examined morphology.