Progoniada cf. regularis Hartman, 1965

Meissner, Karin, Schwentner, Martin, Göưing, Miriam & Fiege, Thomas Knebelsberger and Dieter, 2023, Polychaetes distributed across oceans-examples of widely recorded species from abyssal depths of the Atlantic and Pacific Oceans, Zoological Journal of the Linnean Society 199, pp. 906-944 : 925

Progoniada cf. regularis Hartman, 1965

( Fig. 11A–G )

Progoniada regularis Hartman, 1965 . – Böggemann 2009: 312– 315, figs 46D (neuropodial chaeta), table 7, specimen ZMH-P 25157. – Böggemann 2016: 239–240, fig. 10B–I (anterior to posterior parapodia), specimen SMF 23791.

? Progoniada sp. Böggemann and Sobczyk in Gunton et al. 2021: 47, fig.11, B, D, E.

Material examined: Central Atlantic Ocean, Mid-Atlantic Ridge, East, SO 237 (VEMA Transit), station 4-8, 5737 m (ZMH-P 26694, bad condition). SW Atlantic Ocean, Brazil Basin N, M 79-1 (DIVA 3), station 605-1, 5189 m (SMF 23791, SEM 1339). SE Atlantic Ocean, Angola Basin, M 63-2 (DIVA 2), station 45-5, 5647 m (ZMH-P 25157a(SEM) + 25157b). – for details and additional specimens see the Supporting Information, Table S2 .

Measurements largest specimen studied: Central Atlantic (SMF 23791): length 25 mm, width 0.6 mm, 84 chaetigers.

Description: (Based on specimen SMF 23791.) Prostomium with eight indistinct annulations ( Fig. 11F ). Tip with biarticulate appendages. Eyes absent. Proboscis with paired lateral rows of chevrons (15) ( Fig. 11D ) and doưed with several rows of small cordiform papillae ( Fig. 11E ). Macrognaths with three to four tips. Nine micrognaths arranged in dorsal arc as x-shaped or jointed H + w-shaped pieces and one to two larger jointed H + w-shaped pieces located ventrally ( Fig. 11A–C ).

Parapodia all uniramous ( Fig. 11G ). Prechaetal lobe long, digitiform; postchaetal lobe short, rounded. First segment apodous and with lateral cirri only. Dorsal and ventral cirri digitiform with pointed tip. Ventral cirri slightly longer than dorsal ones. Chaetae compound falcigers and spinigers with long blade ( Fig. 11G ).

Remarks: The specimen collected from the eastern central Atlantic (ZMH-P 26694) is in very bad condition, unsuitable for morphological description. However, the specimens listed here can be separated from specimens of P. regularis based on our genetic results. The specimens collected from Angola Basin (ZMH-P 25157) and Brazil Basin (SMF 23791, SEM stub 1339) were originally included in descriptions of Progoniada regularis Hartman, 1965 by Böggemann (2009, 2016)), respectively. Our molecular data strengthen the view of Böggemann (2009: 318, fig. 48) that P. regularis probably is a complex of cryptic or sibling species. Because our morphological studies of the specimens listed did not reveal significant differences to P. regularis , we refrain from describing a new species solely based on genetic differences.

Distribution: Eastern Central Atlantic (VEMA Fracture Zone) (5735 m, this study), SW ( Brazil Basin) and SE Atlantic ( Angola Basin) (5189 and 5647 m, respectively) (Böggemann 2009, 2016) ( Fig. 3 ).

Magelonidae Cunningham & Ramage, 1888

Figures

Figure 3. Geographic distribution and median-joining COI haplotype networks for Progoniada regularis Hartman, 1965 and P.cf. regularis Hartman, 1965. The colour-code in the network corresponds to the geographic localities, each vertical line represents one mutational step and the size of each haplotype its frequency.Haplotypes are numered 1–11, details are listed in the Supporting Information, Table S2. Available data came from both the Atlantic and Pacific Oceans; the type locality of P.regularis located off New England, NE Atlantic Ocean, is indicated by an asterisk in the map.

Figure 11. Progoniada cf. regularis Hartman, 1965, SEM and LM studies: A, macro- and micrognaths of proboscis. B, macrognaths.C, micrognaths.D, chevrons. E, proboscidial papillae stained with methyl green. F, prostomium, dorsolateral view.G, chaetigers 51–53, posterior midbody, leħ side, anterior view.—A–G, SMF 23791, Brazil Basin N. Scale Bars: A, 200 µm, B, D, F, G, 100 µm, C, E, 50 µm.