Orbiniella mayhemi Meca & Budaeva, 2024

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 mayhemi Meca & Budaeva , sp. nov.

Figs 6 , 7

Clade.

Deep 3.

Type material examined.

Holotype SMF 32627 (DNA voucher Orbi 19) . Paratypes SMF 32588 (1 paratype) ; SMF 32628 (1 paratype on SEM stub) ; SMF 32630 (1 paratype) ; SMF 32640 (1 paratype on SEM stub, DNA voucher Orbi 18) ; ZMBN 157433 (1 paratype, DNA voucher Orbi 3) .

Other material examined.

ZMBN 157432 (3 spms).

Diagnosis.

An Orbiniella with segmental annulation pattern as follows: one narrow annulus between parapodia from parapodium 1 until 5 or 6 and two narrow annuli between parapodia from parapodium 5 or 6 until end of available fragment of the most complete specimen. Acicular spines short and stout, up to three in both noto- and neuropodia. Pygidium not observed.

Type locality.

Irminger Basin, SW Iceland, NE Atlantic, 62.9888, - 28.0950, 1588 m (Fig. 6 ).

Description

(based on type specimens). Holotype incomplete with 14 chaetigers, 3.0 mm long and 0.36 mm wide at level of chaetiger 6. Body elongated and narrow, uniformly wide. Pigmentation lacking in all analysed specimens.

Prostomium broad with rounded anterior margin, without eyespots or nuchal organs (Fig. 7 A ). Peristomium with two prominent achaetous segments, first segment shorter than second segment, distinctly separated from each other and first chaetiger by a narrow annulus (Fig. 7 A ). Anterior chaetigers short, becoming longer and more square-shaped from chaetiger 7–10 onwards. Segmental annulation pattern: one narrow annulus between parapodia from parapodium 1 until 5 or 6 and two narrow annuli between parapodia from parapodium 5 or 6 until end of available fragment of most complete specimen (Fig. 7 E, F ). Posterior part and pygidium not observed.

Parapodia biramous, wider than long, with postchaetal notopodial lobes short, digitate with slightly narrowing basal part, from chaetiger 1 (Fig. 7 B ). Postchaetal neuropodial lobes absent. Crenulated capillary chaetae and acicular spines present in both rami from chaetiger 1. Capillaries equal in length to body width and numerous (6–8 per bundle) in anterior segments; shorter and reduced in number in posterior segments. Capillary chaetae with crenulation occurring on one side along whole chaeta or along half of its length (Fig. 7 D ). Acicular spines short, stout, and smooth, up to three per ramus (Fig. 7 C ).

Variation.

The holotype and most of the paratypes shared the same morphology. However, some paratypes presented more numerous (7–10 per bundle) and longer (longer than body width) capillaries in anterior segments.

Remarks.

Orbiniella mayhemi sp. nov. differs from the other three species described in this work (i. e., O. griegi sp. nov., O. parapari sp. nov., and O. petersenae sensu stricto) in having a body region bearing two narrow annuli between parapodia more extensive than in the other three species. Orbiniella mayhemi sp. nov. also bears short, stout, and smooth spines as O. griegi sp. nov. and O. petersenae sensu stricto, but differing in number (i. e., 1–3 per ramus in O. mayhemi sp. nov.; 1 or 2 in O. griegi sp. nov., and 1–5 in O. petersenae sensu stricto).

Similarly to O. griegi sp. nov., Orbiniella mayhemi sp. nov. resembles the seven deep-sea congeners O. andeepia , O. longilobata , O. rugosa , O. tumida , O. abyssalis , O. armata , and O. mimica in having notopodial postchaetal lobe and in having acicular spines in both noto- and neuropodia. However, O. mayhemi sp. nov. differs from O. abyssalis in having two peristomial segments instead of a single peristomial segment. Among these seven deep-sea species, O. mimica is the closest geographically with O. mayhemi sp. nov. (NW vs NE Atlantic, respectively), being similar in having one or two narrow annuli between parapodia and up to three acicular spines. Orbiniella mimica differs, however, in presenting a papillated dorsal surface on the prostomium and numerous glands in the parapodia and chaetal segments instead of a smooth surface and a uniform digitate notopodial postchaetal lobe instead of a lobe narrowing basally.

Distribution.

From SW to SE Iceland, 913–2505 m (Fig. 6 ).

Etymology.

The species is named in honour to the Norwegian Black Metal band from Oslo, Mayhem, one of the bands that most contributed to the development of the Norwegian Black Metal in the 90 - s. MAM was listening to their music to endure the darkest hours in the lab.

Figures

Figure 6. Distribution of Orbiniella mayhemi Meca & Budaeva, sp. nov. Black lines – Greenland-Scotland Ridge (GSR), star – type locality and the station with examined morphology and molecular data, white plusses – stations with examined morphology.

Figure 7. Orbiniella mayhemi Meca & Budaeva, sp. nov. SEM A paratype SMF 32640, anterior end, dorsal view B paratype SMF 32640, notopodium of chaetiger 7 showing notopodial lobe and capillaries C paratype SMF 32628, neuropodium of chaetiger 5 showing acicular spines and capillaries D paratype SMF 32640, capillary chaetae E paratype SMF 32640, anterior fragment showing narrow annuli between parapodia 1 and 10, dorsal view F paratype SMF 32628, anterior fragment showing narrow annuli between parapodia 1 and 14, ventral view. White arrow in B: Start of crenulation in capillary chaeta. Abbreviations: Ac: acicular spines; Np: notopodial lobe; Par 1: first parapodium; Par 5: fifth parapodium. Scale bars: 100 μm (A, E); 20 μm (B, C); 10 μm (D); 200 μm (F).