Orbiniella petersenae Parapar, Moreira & Helgason, 2015

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 petersenae Parapar, Moreira & Helgason, 2015 , sensu stricto

Figs 11 , 12 , 13

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

Clade.

Deep 1.

Type material examined.

Holotype IINH 35670 . Paratypes IINH 29822 (27 paratypes) , IINH 34897 (1 posterior end of a paratype on SEM stub) , IINH 34899 (9 paratypes) , IINH 35671 (36 paratypes) , IINH 35672 (1 posterior end of a paratype) , IINH 35673 (3 paratypes) , IINH 35699 (6 paratypes on SEM stub) .

Other material examined.

ZMBN 157647 (35 spms); ZMBN 157648 (1 spms); ZMBN 157649 (1 spm on SEM stub); ZMBN 157650 (2 spms on SEM stub); ZMBN 157651 (1 spm); ZMBN 157652 (60 spms); ZMBN 157653 (3 spms); ZMBN 157654 (12 spms); ZMBN 157655 (10 spms); ZMBN 157656 (1 spm); ZMBN 157657 (28 spms); ZMBN 157658 (1 spm); ZMBN 157659 (11 spms); ZMBN 157660 (7 spms); ZMBN 157661 (38 spms); ZMBN 157662 (322 spms); ZMBN 157663 (2 spms on SEM stub); SMF 32584 (2 spms); SMF 32589 (4 spms); SMF 32629 (6 spms); SMF 32632 (23 spms); SMF 32633 (4 spms); SMF 32634 (3 spms); SMF 32635 (3 spms); SMF 32636 (52 spms); SMF 32646 (17 spms); SMF 32647 (41 spms); SMF 32648 (2 spms); SMF 32670 (DNA voucher Orbi 2 on SEM stub); SMF 32671 (DNA voucher Orbi 7); SMF 32672 (DNA voucher Orbi 8); SMF 32673 (DNA voucher Orbi 9); SMF 32675 (DNA voucher Orbi 1); SMF 32676 (DNA voucher Orbi 13); SMF 32677 (DNA voucher Orbi 14); SMF 32678 (DNA voucher Orbi 15 on SEM stub); SMF 32679 (DNA voucher Orbi 16 on SEM stub); SMF 32660 (DNA voucher Orbi 20); IceAGE sample DZMB - HH 33669 (E-voucher NBAAV 667-23).

Diagnosis.

An Orbiniella with segmental annulation pattern as follows: one narrow annulus between parapodium 1 and 2, two narrow annuli between parapodia from parapodium 2 until 5 or 6, and three narrow annuli between parapodia from parapodium 5 or 6 until pygidium. Acicular spines short and stout, up to five in both noto- and neuropodia. Pygidium with four short anal lobes.

Type locality.

Jan Mayen microcontinent, Iceland Sea, 68.8285, - 9.2403, 1849 m (Fig. 11 ).

Remarks.

The morphology of the holotype fully agrees with the original description. The analysis of the IINH paratypes and the new material in this study under a light microscope and SEM allowed elucidating the degree of variability in some morphological characters not discussed by Parapar et al. (2015).

The prostomium shape varied between elongate (Fig. 12 A ) and broad (Fig. 13 A ), both with a rounded anterior margin (Table 1 ). In some specimens from the O. petersenae sensu lato type series material, brownish eyespots with poorly defined borders were observed. Most of the paratypes showed the same type of peristomium as in the holotype (i. e., the first ring shorter than the second one), but a few paratypes were with equal rings. Notopodia varied from digitate, long, and thin (Fig. 12 C ) to digitate, short and thick (Fig. 12 E ). Some of the IceAGE specimens presented the same three patterns of dorsal segmental pigmentation observed in O. parapari , possibly due to better preservation conditions.

SEM micrographs showed one single prominent lateral ciliary congregation at each side of the prostomium, which we interpret as nuchal organs (Fig. 12 B ). Capillary chaetae with crenulation occurring on one side along the whole chaeta or along half of its length (Fig. 12 D, E ). The holotype and the paratypes showed capillaries longer than body width in anterior segments as stated by Parapar et al. (2015). However, some specimens from the material collected in this study presented shorter capillaries equal to body width. Acicular spines were up to five per ramus, instead of up to three reported in Parapar et al. (2015) (Fig. 12 D ).

As mentioned above, among the NE Atlantic / Nordic Orbiniella species, Orbiniella petersenae sensu stricto is most similar to O. parapari sp. nov., furthermore, these two species have an overlapping distribution. As in the case of O. parapari sp. nov., O. petersenae sensu stricto shares a number of morphological characters with the seven deep-sea congeners: O. andeepia , O. longilobata , O. rugosa , O. tumida , O. abyssalis , O. armata , and O. mimica (see remarks section of O. parapari sp. nov. for comparison of the two species). One sample from a station near Jan Mayen (1243 m) contained an outstanding number of O. petersenae sensu stricto (i. e., 322 specimens).

Distribution.

Iceland Sea and southern Greenland Sea, 1053–2407 m. Possibly Norwegian Sea, 2525–3892 m (Fig. 11 ).

Figures

Figure 11. Distribution of Orbiniella petersenae sensu stricto. Black lines – Greenland-Scotland Ridge (GSR), star – type locality, coloured circles – stations with examined morphology and molecular data, white circles – stations with examined morphology.

Figure 12. Orbiniella petersenae sensu stricto, SEM A paratype ZMBN 157649, anterior end, dorsal view B paratype ZMBN 157649, detail of left lateral side of prostomium showing presumed nuchal organs (insert of A) C paratype SMF 32678, notopodium of chaetiger 3 showing notopodial lobe and capillaries D paratype SMF 32678, neuropodim of chaetiger 7 showing acicular spines and capillaries E paratype ZMBN 157663, notopodium of chaetiger 10 showing notopodial lobe, acicular spines, and capillaries F paratype SMF 32678, detail of capillary chaetae. White and black arrows in A: Lateral ciliary spots; White arrow in E: Start of crenulation in capillary chaeta. Abbreviations: Ac: acicular spines; Np: notopodial lobe. Scale bars: 100 μm (A – C); 40 μm (D); 50 μm (E); 10 μm (F).

Figure 13. Orbiniella petersenae sensu stricto, SEM A paratype ZMBN 157663, anterior end, ventral view showing narrow annuli between parapodia 1 and 7 B paratype ZMBN 157650, midbody, ventral view showing narrow annuli between parapodia 17 and 24 C paratype ZMBN 157650, posterior end, ventral view D paratype ZMBN 157650, detail of last two chaetigers together with pygidium (insert of C). Numbers indicate narrow annuli between parapodia. Abbreviations: Par 1: first parapodium; Par 6: sixth parapodium. Scale bars: 500 μm (A); 100 μm (B, C); 20 μm (D).