Prionospio fiordica, 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 : 29-34

Prionospio fiordica sp. nov.

urn:lsid:zoobank.org:act:

Figs 12–14

Prionospio sp. 3 – Hektoen et al. 2024: figs 1, 4.

Diagnosis

Prostomium triangular, anteriorly wide, truncate, posteriorly extending to end of chaetiger 1 as a short caruncle. Two pairs of small eyes present. Branchiae from chaetiger 2 to chaetigers 10–14, cirriform, apinnate, longest on the first chaetiger and then gradually diminishing in size. Dorsal crests low, on chaetigers 12–16. Neuropodial postchaetal lamellae of chaetiger 2 not elongated ventrally, large and rectangular on chaetigers 3–4. Sabre chaetae in neuropodia from chaetigers 16–17. Hooded hooks in notopodia from chaetiger 34, in neuropodia from chaetigers 17–18.

Etymology

The name ‘ fiordica ’ refers to the type locality and common occurrence of the species in the Norwegian fjords.

Type material

Holotype

NORWAY • Vestland , Stad, Midthjell; 61°55.306′ N, 5°32.774′ E; depth 576 m; 20 Apr. 2022; STIM AS leg.; stn C5.2; van Veen grab; NTNU-VM 84107 .

Paratypes

NORWAY • 2 specs; Vestland , Stad, Midthjell; 61°55.232′ N, 5°31.303′ E; depth 580 m; 20 Apr. 2022; STIM AS leg.; stn C3.1; van Veen grab; NTNU-VM 84111 • 4 specs; Møre og Romsdal, Volda, Voldsfjorden; 62°6.058′ N, 6°7.302′ E; depth 462 m; 14 Dec. 2021; STIM AS leg.; stn LOK C-REF; van Veen grab; NTNU-VM 84110 • 3 specs; Stad , Juvika B; 61°53.747′ N, 5°39.023′ E; depth 559 m; 9 Dec. 2021; Åkerblå AS leg.; stn JUV-2; van Veen grab; NTNU-VM 84114 .

Paratypes with sequence data

NORWAY • 1 spec.; Stranda, Opshaugvik; 62°17.350′ N, 6°59.630′ E; depth 376 m; 31 Mar. 2020; Åkerblå AS leg.; stn OPS-3.1; van Veen Grab; NTNU-VM 84105 • 1 spec.; Alver, Trollholmen; 60°30.978′ N, 5°10.434′ E; depth 367 m; 13 Aug. 2019; Rådgivende Biologer AS leg.; stn C1; van Veen grab; NTNU-VM 84101 .

Other material examined

NORWAY – Møre og Romsdal • 1 spec.; Kinn, Brunsvik ; 61°54.238′ N, 5°17.256′ E; depth 389 m; 14 Dec. 2020; Åkerblå AS leg.; stn BRU-6.1; van Veen Grab; NTNU-VM 84112 • 3 specs; Hareid, Uravika; 62°24.006′ N, 6°1.933′ E; depth 435 m; 23 Oct. 2021; Åkerblå AS leg.; stn URA-4; van Veen grab; NTNU-VM 84108 • 2 specs; Tingvoll, Halsbukta ; 63°4.952′ N, 8°8.815′ E; depth 343 m; 4 Mar. 2021; Åkerblå AS leg; stn HAL-3.2; van Veen grab; NTNU-VM 84106 • 1 spec.; same data as for preceding; SEM stub; NTNU-VM 85854 • 1 spec.; Rauma, Skarbukta ; 62°35.870′ N, 7°22.444′ E; depth 414 m; 28 Oct. 2021; Åkerblå AS leg.; stn SKA-4; van Veen grab; NTNU-VM 84109 • 1 spec.; Hareid, Uravika; 62°23.610′ N, 6°2.911′ E; depth 446 m; 23 Oct. 2021; Åkerblå AS leg.; stn URA-6; van Veen grab; NTNU-VM 84113 . – Vestland • 1 spec.; Masfjorden, Laberget; 60°44.922′ N, 5°17.400′ E; depth 450 m; 13 May 2019; Rådgivende Biologer AS leg.; stn C2B; van Veen grab; NTNU-VM 84099 • 2 specs; same data as for preceding; NTNU-VM 84100 • 1 spec.; Øygarden, Sund ; 60°11.061′ N, 5°11.737′ E; depth 665 m; 26 Apr. 2017; Bergen University Museum leg.; stn KB-03; van Veen grab; ZMBN 152607 • 1 spec.; Kvinnherad Hondskår; 60°6.282′ N, 5°56.262′ E; depth 378 m; 3 May 2018; Rådgivende Biologer AS leg.; stn C3B; van Veen grab; NTNU-VM 84103 • 2 specs; same data as for preceding; NTNU-VM 84104 • 4 specs; Masfjorden, Laberget; 60°44.922′ N, 5°17.400′ E; depth 450 m; 13.05.2019; Rådgivende Biologer AS leg.; stn C2B; van Veen grab; NTNU-VM 84102 • 2 specs; Hyllestad Sognefjorden ; 61°3.0072′ N, 5°24.034′ E; depth 1236 m; 3 May 2017; Bergen University Museum leg.; stn KB 2017-05-02; van Veen grab; ZMBN 152609 • 3 specs; Øygarden, Sund ; 60°11.061′ N, 5°11.737′ E; depth 665 m; 26 Apr. 2017; Bergen University Museum leg.; kb-03; van Veen grab; ZMBN 152611 .

Examined material with sequence data

NORWAY – Vestland • 1 spec.; Øygarden, Sund ; 60°11.061′ N, 5°11.737′ E; depth 665 m; 26 Apr. 2017; Bergen University Museum leg.; stn KB-02; van Veen grab; ZMBN 152612 • 1 spec.; Lustrafjorden ; 61°22.136′ N, 7°23.070′ E; depth 374 m; 5 May 2017; Bergen University Museum leg.; stn kb 2017-05- 25 AG; van Veen grab; ZMBN 152608 • 1 spec.; Bømlo ; 59°34.331′ N, 5°13.813′ E; depth 340 m; 28 Apr. 2017; Bergen University Museum leg.; stn KB-22; van Veen grab; SEM stub; ZMBN 152647 • 1 spec.; Hyllestad Sognefjorden ; 61°3.0072′ N, 5°24.034′ E; depth 1236 m; 3 May 2017; Bergen University Museum leg.; stn KB 2017-05-02; van Veen grab; ZMBN 152613 • 1 spec.; Hyllestad, Åfjorden ; 61°12.784′ N, 5°2.285′ E; depth 379 m; 14 Jul. 2015; Bergen University Museum leg.; stn HM 2015- 07-15 GR; van Veen grab; ZMBN 117450 • 1 spec.; Øygarden, Sund ; 60°11.061′ N, 5°11.737′ E; depth 665 m; 26 Apr. 2017; Bergen University Museum leg.; kb-03; van Veen grab; ZMBN 152606 • 1 spec.; Austevoll, Bakkasund ; 60°9.105′ N, 5°5.913′ E; depth 616 m; 26 Apr. 2017; Bergen University Museum leg.; stn KB-06; van Veen grab; ZMBN 152610 • 1 spec.; Bømlo ; 59°34.037′ N, 5°12.941′ E; depth 328 m; 28 Apr. 2017; Bergen University Museum leg.; stn KB-20; van Veen grab; ZMBN 152605 .

Description (adults)

Holotype ( NTNU-VM 84107), anterior fragment, 8 mm long, 0.3 mm wide, with 40 chaetigers ( Fig. 12). Paratypes and other anterior fragments of specimens with fewer segments, some lost branchiae and lamellae during fixation and handling. Color in alcohol pale white. Prostomium triangular, anteriorly truncate, posteriorly extending to end of chaetiger 1 as short, thick caruncle ( Figs 12, 13A). Nuchal organs U-shaped ciliary bands lateral to caruncle. Two pairs of small eyes arranged trapezoidally ( Fig. 12). Eyespots faint or become invisible after fixation in formalin; bright red spots when preserved directly in ethanol. Peristomium fused with notopodial lamellae of chaetiger 1, enclosing prostomium laterally. Palps missing in all specimens.

Branchiae from chaetiger 2 to chaetigers 9–13 (on chaetigers 2–11 in holotype), cirriform, apinnate, with lateral ciliation. First pair of branchiae usually longest, about 2.5–3 × as long as length of the notopodial postchaetal lamellae; branchiae gradually diminishing in size on following chaetigers ( Figs 13A–B, 14B–H). Branchiae of chaetigers 3–6 slightly longer than notopodial postchaetal lamellae, twice as long as notopodial postchaetal lamellae by chaetiger 10. Nototrochs transverse ciliary bands between branchial bases. Dorsolateral longitudinal ciliation absent.

Notopodial prechaetal lamellae small, rounded in anterior chaetigers. Notopodial postchaetal lamellae of chaetiger 1 broadly rounded, fused with peristomium; lamellae subtriangular on chaetigers 2–9, largest, often with slender tips on chaetigers 3–5. Lamellae decreasing in size and becoming rounder on chaetigers 10–12 ( Fig. 14A–I). On chaetigers 12–16, notopodial postchaetal lamellae extending middorsally and joining in the middle forming low crests. Neuropodial prechaetal lamellae inconspicuous. Interneuropodial pouches absent. Neuropodial postchaetal lamellae of chaetiger 1 small, oblong ( Fig. 14A); lamellae of chaetiger 2 large and trapezoidal with rounded edges, not elongated ventrally ( Fig. 14B), subrectangular on chaetigers 3 and 4 ( Fig. 14C–D), from chaetiger 5 evenly rounded ( Fig. 14E–I), from chaetiger 13 low and oval.

Notopodial capillaries on anterior and middle chaetigers arranged in two rows, unilimbate and granulated. Neuropodial capillaries arranged in two rows in anterior chaetigers, unilimbate and granulated; anterior row shorter than posterior row in both rami. Chaetae on posterior chaetigers not observed. Sabre chaetae in neuropodia from chaetigers 16–17 (chaetiger 17 in holotype), up to two per fascicle, with granulation on distal part of shaft ( Fig. 14K). Hooded hooks in notopodia present only in holotype, from chaetiger 34 onwards (other specimens are shorter anterior fragments). Hooded hooks first appearing in neuropodia from chaetigers 17–18 (chaetiger 18 in holotype), alternating with capillary chaetae. Neuropodial hooded hooks usually appear in next chaetiger after the first sabre chaetae, up to eight in series. Both noto- and neuropodial hooks with 4–5 pairs of small upper teeth arranged in two vertical rows above main fang ( Fig. 14J), with outer and a small inner hoods.

Pygidium missing in all specimens.

Remarks

Fixed specimens of Prionospio fiordica sp. nov. are fragile, making detailed study challenging. All specimens were anterior fragments, often damaged, lacking notopodial postchaetal lamellae and branchiae. Only the holotype had more than 30 chaetigers and was the only specimen with hooded hooks in notopodia. The species was sequenced by Hektoen et al. (2024) and was found to be genetically different from all other species studied.

Prionospio fiordica sp. nov. can be distinguished from P. multibranchiata (based on the redescription by Delgado-Blas et al. 2018) primarily by the dorsal crests (present in P. fiordica sp. nov. and absent in P. multibranchiata ). Other differences include the shape of the eyes (small and represented by single eyespots in the former and large and conspicuous in the latter). It can be distinguished from P. maciolekae (based on the description by Dagli & Çinar, 2011) by the shape of prostomium (triangular, anteriorly truncate in P. fiordica and subrectangular, anteriorly rounded in P. maciolekae ), the shape of the neuropodial postchaetal lamellae of chaetiger 3 (broadly rounded in the former and narrowly rounded, becoming finger-like in the latter).

Prionospio fiordica sp. nov. can be distinguished from P. sanmartini primarily by the shape of prostomium (triangular and truncate anteriorly with a short thick caruncle in the former, and anteriorly rounded, widest just before the lateral eyes, with a narrow caruncle in the latter), and the shape of the peristomium (more developed in P. fiordica ). Other differences include the shape of eyes (always indistinct small single spots in the former, and larger in the latter), and sabre chaetae and hooded hooks in neuropodia, generally starting later in P. fiordica (from chaetigers 16–17 and 17–18, respectively) than in P. sanmartini (from chaetigers 12–17 and 13–18).

Prionospio fiordica sp. nov. was referred in the molecular study by Hektoen et. al. (2024) as Prionospio sp. 3 . The species is genetically distinct from multibranchiate Prionospio from Skagerrak and southern Europe ( Prionospio cf. sanmartini in Hektoen et al. 2024, assigned here to P. sanmartini ), and from the Eastern and Western Pacific (referred in Hektoen et al. 2024 as P. multibranchiata ). Based on the current data, there seems to be a geographic and bathymetric separation between P. fiordica and P. sanmartini , where P. sanmartini has not yet been recorded from Western Norway, and not deeper than 118 m, while P. fiordica has exclusively been found in fjords and offshore western Norway deeper than 328 m.

Habitats and distribution

Adults of P. fiordica sp. nov. were collected from the northern part of the North Sea and southern part of the Norwegian Sea, both offshore and in fjords in Vestland and Møre og Romsdal counties of Norway. They were found in fine silt and muddy sediments at depts of 328–1236 m. The conspecificity of individuals from such a wide bathymetric range was confirmed with molecular analysis by Hektoen et al. (2024).