Prionospio sigvaldadottirae, Hektoen & Radashevsky & Bakken, 2025

Hektoen, Martin M., Radashevsky, Vasily I. & Bakken, Torkild, 2025, Partial revision of northern European Prionospio Malmgren, 1867 (Annelida: Spionidae), European Journal of Taxonomy 1027, pp. 1-58 : 40-45

Prionospio sigvaldadottirae sp. nov.

urn:lsid:zoobank.org:act:

Figs 18–20; Table 2

Prionospio sp. 7 – Hektoen et al. 2024: figs 1, 4.

Diagnosis

Prostomium anteriorly truncate, posteriorly extending to end of chaetiger 2 as a narrow caruncle. Four pairs of branchiae on chaetigers 2–5; those on chaetiger 2 long, with lateral pinnules, on chaetiger 5 long or shorter, with lateral pinnules, on chaetigers 3 and 4 shorter, apinnate. Dorsal crests from chaetiger 7 to chaetigers 20–22, highest on chaetiger 7. Neuropodial postchaetal lamellae of chaetiger 2 pointed and elongated ventrally. Sabre chaetiger in neuropodia from chaetiger 10. Hooded hooks in notopodia from chaetigers 43–58, in neuropodia from chaetigers 15–17.

Etymology

The species is named in honor of Dr Elin Sigvaldadóttir, an Icelandic zoologist who made a great contribution to the study of the Northeastern Atlantic Prionospio .

Type material

Holotype

NORWAY • Norwegian Sea , Vigdis D oil field; 61°21.000′ N 2°4.200′ E; depth 246 m; Aug.–Sep. 2020; STIM AS leg.; stn VTD-10; van Veen grab; NTNU-VM 84143 .

Paratypes

NORWAY • 6 specs; Norwegian Sea, Vigdis D oil field; 61°22.009′ N, 2°2.079′ E; depth 246 m; 31 May 2014; STIM AS leg.; stn VTD-R; van Veen grab; NTNU-VM 84145 • 2 specs; Norwegian Sea, Vigdis D oil field; 61°21.000′ N, 2°4.200′ E; depth 246 m; Aug.–Sep. 2020; STIM AS leg.; stn VTD-10; van Veen grab; NTNU-VM 84144 • 6 specs; Norwegian Sea, Vigdis D oil field; 61°20.923′ N, 2°4.176′ E; depth 248 m; Aug.–Sep. 2020; STIM AS leg.; stn VTD-12; van Veen grab; NTNU-VM 84146 • 1 spec.; Vigdis D oil field; 61°20.923′ N, 2°4.176′ E; depth 248 m; Aug.–Sep. 2020; STIM AS leg.; stn VTD-12; van Veen grab; SEM stub; NTNU-VM 85860 .

Other material examined

NORWAY – Norwegian Sea • 1 spec.; Vigdis D oil field; 61°20.923′ N, 2°4.176′ E; depth 250 m; 31 May 2014; STIM AS leg.; stn VTD12_14; van Veen grab; ZMBN 105363 • 1 spec.; Vigdis D oil field; 61°21.000′ N, 2°4.200′ E; depth 246 m; Aug.–Sep. 2020; STIM AS leg.; stn VTD-10; van Veen grab; SEM stub; NTNU-VM 85859 .– North Sea • 1 spec.; Oseberg oil field; 60°27′ N, 2°43′ E; depth 104 m; 14 Apr. 1983; stn A10.5; van Veen grab; NTNU-VM 25276 • 1 spec.; Oseberg oil field; 60°27′ N, 2°43′ E; depth 104 m; 5 Jul 1983; stn b7.4; van Veen grab; NTNU-VM 25285 • 1 spec.; Oseberg oil field; 60°27′ N, 2°43′ E; depth 104 m; 5 Jul. 983; stn b5.7; van Veen grab; NTNU-VM 25287 • 1 spec.; Oseberg oil field; 60°27′ N, 2°43′ E; depth 104 m; 5 Jul. 1983; stn b1.gr1; van Veen grab; NTNU-VM 25286 • 1 spec.; Oseberg oil field; 23 Feb. 1984; van Veen grab; NTNU-VM 25275 • 1 spec.; Oseberg oil field; 17 Feb. 1984; van Veen grab; NTNU-VM 25217 .

Examined material with sequence data

NORWAY – Norwegian Sea • 1 spec.; Vigdis D oil field; 61°20.923′ N, 2°4.176′ E; depth 250 m; 31 May 2014; STIM AS leg.; stn VTD12_14; van Veen grab; ZMBN 152646 .

SENEGAL • 1 spec.; 14°27.576′ N, 17°36.624′ W; depth 489 m; 5 Nov. 2011; CCLME leg.; stn 2011410- GR08; van Veen grab; ZMBN 152649 .

WESTERN SAHARA • 1 spec.; 25°5.100′ N, 16°18.612′ W; depth 568 m; 25 Nov. 2011; CCLME leg.; stn 2011410-GR20; van Veen grab; ZMBN 152648 .

Description (adults)

Holotype ( NTNU-VM 84143) anterior fragment, 12 mm long, 0.8 mm wide, with 37 chaetigers ( Fig. 18). Longest complete specimen 16 mm long with 55 chaetigers; smallest specimen 0.3 mm wide. Color in alcohol pale white. Prostomium rectangular, anteriorly truncate, with small ciliated tubercles on frontal edge, posteriorly extending to end of chaetiger 2 as long narrow caruncle ( Fig. 19A). Nuchal organs prominent V-shaped ciliary bands lateral to caruncle. Two pairs of red-brown eyes arranged trapezoidally; median eyes large, often crescent-shaped ( Fig. 19C), sometimes as single or multiple small spots; lateral eyes single round spots. Posterior dorsolateral parts of peristomium fused with notopodial postchaetal lamellae of chaetiger 1 forming ear-shaped structures lateral to prostomium. Palps missing in all specimens.

Branchiae on chaetigers 2–5 ( Figs 18, 19A–C, 20B–E); those on chaetiger 2 long, cylindrical, with digitiform pinnules; pinnules approximately two thirds to three fourths up branchiae, arranged in lateral rows except for the base where often present also on posterior side ( Fig. 20B, E). Branchiae of chaetiger 5 in holotype half the length of branchiae on chaetiger 2, in other specimens varying from half length to similar in length to branchiae on chaetiger 2 ( Figs 18, 19B–C); pinnules about halfway to two thirds up branchiae; otherwise similar to branchiae on chaetiger 2. Branchiae of chaetigers 3 and 4 apinnate, similar in lengths to notopodial postchaetal lamellae, flat, with surface perpendicular to body axis, with dense lateral ciliation. Nototrochs transverse ciliary bands between branchial bases on chaetigers 3 and 4. Dorsolateral longitudinal ciliation between chaetigers 3–7 ( Fig. 19A).

Notopodial prechaetal lamellae large and oval, conspicuous on anterior chaetigers ( Fig. 19A) until about chaetiger 25, gradually reduced on posterior chaetigers. Notopodial postchaetal lamellae of chaetiger 1 triangular, fused with peristomium ( Fig. 20A); lamellae of chaetigers 2–5 large and subtriangular, largest on chaetiger 3 ( Fig. 20B–E); diminishing in size on postbranchial chaetigers, low and rounded from chaetiger 8 onwards. Notopodial postchaetal lamellae extending middorsally and forming low transverse crests from chaetiger 7 to chaetigers 20–22 ( 21 in holotype); crest significantly higher on chaetiger 7 than on subsequent chaetigers ( Fig. 20G–H). Dorsolateral membranous folds absent. Lateral swelling between anterior postbranchial chaetigers sometimes present ( Fig. 19A). Neuropodial prechaetal lamellae large and rounded, conspicuous to approximately chaetiger 20. Neuropodial prechaetal lamellae extending slightly onto ventral side from chaetigers 8–10 to 16–24 ( 9–20 in holotype) ( Fig. 20H). Neuropodial postchaetal lamellae of chaetiger 1 small, broadly rounded ( Fig. 20A); lamellae of chaetiger 2 subtriangular, with acute ventral point ( Fig. 20B); lamellae of chaetiger 3 trapezoid, with rounded edges ( Fig. 20C). Lamellae of subsequent chaetigers evenly rounded ( Fig. 20D–H). Neuropodial postchaetal lamellae largest on chaetigers 2 and 3, diminishing in size posteriorly, lower and broader from chaetiger 8. Interneuropodial pouches absent.

Notopodial capillaries on anterior and middle chaetigers arranged in three rows, unilimbate and smooth. Neuropodial capillaries arranged in two rows in anterior chaetigers, unilimbate and smooth. In both rami, anterior row of capillaries shorter than those in posterior rows. Capillary chaetae in posterior chaetigers not observed. Sabre chaetae in neuropodia from chaetiger 10, with slight granulation on median and distal parts of shaft, usually one, occasionally two per fascicle ( Fig. 19D). Hooks in notopodia from chaetigers 36–47 ( NTNU-VM 84145), not present in holotype. Hooks in neuropodia from chaetigers 16–18 (chaetiger 17 in holotype), up to eight in a series, alternating with capillary chaetae. Both noto- and neuropodial hooks with 4–6 pairs of upper teeth arranged in two vertical rows above main fang, with outer and a small inner hoods.

Pygidium missing in all specimens.

Remarks

Prionospio sigvaldadottirae sp. nov. belongs to the large Prionospio steenstrupi group, comprising more than 40 species. The group is characterized by having pinnate branchiae on chaetigers 2 and 5 and apinnate branchiae on chaetigers 3 and 4. Twelve species of this group have dorsal crests starting from, but not limited to, chaetiger 7, like in P. sigvaldadottirae sp. nov. (see Table 2). Prionospio sigvaldadottirae is most similar to Prionospio depauperata Imajima, 1990 from Japan in having an anteriorly truncate prostomium extending back to end of chaetiger 2, dorsal crests starting from chaetiger 7, and sabre chaetae from chaetiger 10. Prionospio sigvaldadottirae can be distinguished from P. depauperata by having pinnules up half the length of the branchiae on chaetiger 5 or more (rather than the basal third), hooded hooks in neuropodia from chaetigers 16–18 (rather than 15–16), and dorsal crests always extending at least to chaetiger 20 (rather than to chaetiger 13).

Adults of P. sigvaldadottirae sp. nov. were previously misidentified as P. steenstrupi in environmental monitoring surveys in Norway (lead author personal observation). Prionospio sigvaldadottirae sp. nov. can be readily distinguished from P. steenstrupi by having dorsal crests from chaetiger 7 rather than from chaetiger 6, the dorsal crest being significantly higher on chaetiger 7 than on subsequent chaetigers, and by lacking membranous folds between anterior notopodia. Based on our study of Icelandic material, these dorsolateral folds were present in all Icelandic P. steenstrupi , regardless of size. Some specimens of P. sigvaldadottirae have lateral swellings between parapodia of postbranchial chaetigers ( Fig. 19A). These swellings might be similar to what Blake (1996) described for Californian specimens identified by him as P. steenstrupi . However, since Blake (1996) did not illustrate these swellings, their similarity in Californian and Norwegian specimens remains uncertain. They are either way clearly different from the dorsolateral membranous folds of Icelandic P. steenstrupi (see remarks for P. steenstrupi below). Like Blake (1996), we are not sure if these swellings are a preservation artifact, thus the examination of live specimens is needed to clarify this.

Our previous study ( Hektoen et al. 2024) confirmed the conspecificity of specimens (referred as Prionospio sp. 7 ) from Norway, Western Sahara and Senegal collected from 248–568 m depth. Additional formalin-fixed specimens reported here were all from offshore Norway, some from the same exact location as the sequenced specimen.

Habitats and distribution

Prionospio sigvaldadottirae sp. nov. is known from offshore Norway, Western Sahara and Senegal, from 104–568 m depth.