Prionospio fallax Söderström, 1920

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 : 20-24

Prionospio fallax Söderström, 1920

Fig. 8

Prionospio fallax Söderström, 1920: 235–237 , figs 135, 144–145.

Prionospio malmgreni – Eliason 1920: 51, fig. 13a–b. — Fauvel 1927: 61–62, fig. 21a–c. — Hannerz 1956: 40–46, figs 12–13.

Prionospio fallax – Sigvaldadóttir & Mackie 1993: 207–211, figs 3–5. — Kirkegaard 1996: 82–83, fig. 37 — Hektoen et al. 2024: figs 1, 4.

Diagnosis

Prostomium anteriorly truncate, posteriorly extending to end of chaetiger 1 as a thick caruncle. Two pairs of dark red eyes (appear black when fixed in ethanol or formalin); median eyes small single spots to large patches; lateral eyes single spots. Four pairs of branchiae on chaetigers 2–5; branchiae of chaetigers 2 and 5 long, pinnate, with pinnules arranged in single lateral rows; branchiae of chaetigers 3 and 4 apinnate, similar in size to notopodial postchaetal lamellae. Dorsolateral longitudinal ciliation present between successive notopodia on chaetigers 4–7. High dorsal crest on chaetiger 7 only. Neuropodial postchaetal lamellae of chaetiger 2 elongated ventrally. Sabre chaetae in neuropodia from chaetiger 10. Hooded hooks in neuropodia from chaetigers 12–13.

Type material

Lectotype

SWEDEN • Bohuslän, Lysekil, Islandsberg; 1891; A. Wirén leg.; designated by Sigvaldadóttir & Mackie (1993); UPSZTY 2255 .

Paralectotypes

SWEDEN • 11 specs; Bohuslän, Lysekil, Islandsberg; 1891; A. Wirén leg.; designated by Sigvaldadóttir & Mackie (1993); UPSZTY 2255.

Other material examined

FRANCE • 14 specs; Banyuls-sur-Mer ; 42°29.000′ N, 3°9.000′ E; depth 32 m; 1991; F. Pleijel leg.; Banyuls 2; van Veen grab; SMNH 111902 • 9 specs; Banyuls-sur-Mer ; 42°30.000′ N, 3°9.000′ E; depth 4 m; 1991; F. Pleijel leg.; van Veen grab; SMNH 111900 • 18 specs; Banyuls-sur-Mer ; 42°30.102′ N, 3°9.288′ E; depth 40 m; 7 Oct. 1991; F. Pleijel leg.; stn Banyuls 1991c; van Veen grab; SMNH 180570 .

ITALY • 17 specs; Siracusa, Brucoli ; 37°16.300′ N, 15°11.500′ E; depth 60 m; 23 May 1990; F. Pleijel leg.; stn Sicily 7; van Veen grab; SMNH 180568 • 10 specs; Catania ; 37°35.500′ N, 15°11.800′ E; depth 140 m; 18 May 1990; F. Pleijel leg.; stn Acitrezza 7; van Veen grab; SMNH 180567 .

NORWAY – Skagerrak • 8 specs; Oslofjorden; 28 Mar. 1952; van Veen grab; NHMO. – Østfold • 10 specs; Halden, Sponvika; 59°5.500′ N, 11°11.000′ E; depth 85 m; 23 Sep. 1992; stn Singlefjord 1992; van Veen grab; SMNH 111896 • 1 spec.; Halden, Sponvika; depth 25 m; 16 Sep. 1984; stn Sponvika 2; van Veen grab; SMNH 111883 . – Akershus • 1 spec.; Frogn, Drøbak; 59°38.682′ N, 10°37.302′ E; depth 10–45 m; 22 Oct. 2014; stn POLYSKAG 2014/10-18; van Veen grab; ZMBN 152633 . – Vestfold • 1 spec.; Larvik; 59°2.667′ N, 10°1.537′ E; depth 43 m; 2020; NIVA leg.; stn lar-S27; van Veen grab; NTNU-VM 84043 • 4 specs; Holmestrand, Sande; 59°32.952′ N, 10°16.932′ E; depth 20–29 m; 30 May 2011; ZMBN leg; stn TR6; van Veen grab; ZMBN 152631 • 14 specs; 58°49.716′ N, 10°34.626′ E; depth 127–148 m; 17 May 2009; ZMBN leg.; stn BS48-82; sledge; ZMBN 152630 . – Telemark • 1 spec.; Brevik, 59°3.620′ N, 9°41.891′ E; depth 10 m; 26 Aug. 2019; T. Bakken leg.; stn 2019091; van Veen grab; NTNU VM 77612. – Agder • 3 specs; Kristiansand, Skoltebukta; 58°7.503′ N, 7°58.788′ E; depth 31 m; 2020; NIVA leg.; stn K17; van Veen grab; NTNU-VM 84115 • 1 spec.; Tvedestrand, Sandvika; 58°34.080′ N, 9°1.860′ E; depth 22 m; 27 May 2011; NIVA leg.; stn GR3; van Veen grab; ZMBN 152616 . – Vestland • 2 specs; Alver, Jibbersholmen; 60°45.052′ N, 4°53.330′ E; depth 80 m; 18 Dec. 2019; Åkerblå AS leg.; stn JIB-4; van Veen grab; NTNU-VM 84095 • 3 specs; Alver, Jibbersholmen; 60°45.169′ N, 4°53.273′ E; depth 115 m; 18 Dec. 2019; Åkerblå AS leg.; stn JIB-1; van Veen grab; NTNU-VM 84063 • 5 specs; Gulen, Hardbakkeneset; 61°1.035′ N, 4°56.645′ E; depth 110 m; 19 Sep. 2019; Åkerblå AS leg.; stn HAR-3; van Veen grab; NTNU-VM 84067 • 1 spec.; Fjaler, Hegnes; 61°21.470′ N, 5°17.110′ E; depth 243 m; 4 Dec. 2019; Åkerblå AS leg.; stn HEG-1; van Veen grab; SEM stub; NTNU-VM 84157 • 1 spec.; same data as for preceding; SEM stub; NTNU-VM 84158 • 1 spec.; Fjaler, Hegnes; 61°21.579′ N, 5°17.270′ E; depth 244 m; 4 Dec. 2019; Åkerblå AS leg.; stn Heg-2; van Veen grab; NTNU-VM 84050 • 17 specs; same data as for preceding; NTNU-VM 84051 • 15+ specs; Bremanger Gulestø; 61°45.701′ N, 5°4.096′ E; depth 146 m; 8 Oct. 2019; Åkerblå AS leg.; stn GUL-3; van Veen grab; NTNU-VM 84059 • 11 specs; Bremanger Gulestø; 61°45.868′ N, 5°4.050′ E; depth 170 m; 8 Oct. 2019; Åkerblå AS leg.; stn GUL-2; van Veen grab; NTNU-VM 84057 • 10 specs; Sogndal, Beitveit; 62°8.171′ N, 5°19.906′ E; depth 138 m; 10 Oct. 2019; Åkerblå AS leg.; stn BEI-3; van Veen grab; NTNU-VM 84097 • 20 specs; Sogndal, Beitveit; 62°8.551′ N, 5°20.113′ E; 10 Oct. 2019; Åkerblå AS leg.; stn BEI-5; van Veen grab; NTNU-VM 84040 • 1 spec.; Bergen, Mortholmosen; 60°12.864′ N, 5°20.736′ E; depth 42–60 m; 9 Feb. 2006; ZMBN leg.; stn HB 2006.02.09 -2; sledge; ZMBN 152620 • 17 specs; Øygarden, Sund; 60°10.080′ N, 5°0.420′ E; depth 17 m; 23 Apr. 2014; ZMBN leg.; stn HB 2014.04.24 -3; van Veen grab; ZMBN 152627 • 1 spec.; Øygarden, Sund; 60°10.380′ N, 5°0.180′ E; depth 6 m; 23 Apr. 2014; ZMBN leg.; stn HB 2014.04.24 -4; van Veen grab; ZMBN 152626 • 50+ specs; Øygarden, Sund; 60°12.000′ N, 5°2.460′ E; depth 60 m; 23 Apr. 2014; ZMBN leg.; stn HB 2014.04.24 -5; van Veen grab; ZMBN 152623 • 35 specs; Øygarden, Sund; 60°12.046′ N, 5°2.305′ E; depth 30–60 m; 7 Sep. 2016; ZMBN leg.; stn HB 2016.09.07 -2; sledge; ZMBN 152621 • 7 specs; Bergen, Flesland; 60°17.052′ N, 5°12.087′ E; depth 72 m; 2 Sep. 2014; ZMBN leg.; stn HB 2014.09.02 - 1; van Veen grab; ZMBN 152625 • 37 specs; Alver, Håøysundet; 60°32.984′ N, 5°13.738′ E; depth 37 m; 20 Apr. 2017; ZMBN leg.; stn HB 2017.04.20 -2; van Veen grab; ZMBN 152632 • 3 specs; Alver, Radfjorden; 60°36.009′ N, 5°9.262′ E; depth 106m; 6 Mar. 2017; ZMBN leg.; stn HB 2017.03.06 -5; van Veen grab; ZMBN 152624 . – Møre og Romsdal • 10 specs; Rauma, Lybergsvika; 62°38.678′ N, 7°26.648′ E; depth 104 m; 18 Jul. 2019; Åkerblå AS leg.; stn LYB-5; van Veen grab; NTNU-VM 84058 • 5 specs; Rauma, Lybergsvika; 62°38.777′ N, 7°27.359′ E; depth 95 m; 18 Jul. 2019; Åkerblå AS leg.; stn LYB-6; van Veen grab; NTNU-VM 84056 • 1 spec.; Kristiansund, Or; 63°2.087′ N, 7°50.760′ E; depth 60 m; 13 Nov. 2019; Åkerblå AS leg.; stn OR-2; van Veen grab; NTNU-VM 84159 • 2 specs; same data as for preceding; NTNU-VM 84047 • 4 specs; Kristiansund, Or; 63°2.527′ N, 7°51.402′ E; depth 56 m; 13 Nov. 2019; Åkerblå AS leg.; stn OR-4; van Veen grab; NTNU-VM 84046 • 1 spec.; Smøla, Andholmane; 63°28.525′ N, 7°51.111′ E; depth 53 m; 17 Dec. 2019; Åkerblå AS leg.; stn AND-8; van Veen grab; NTNU-VM 84042 • 1 spec.; same data as for preceding; SEM stub; NTNU-VM 85853 . – Trøndelag • 1 spec.; Trondheim, Grillstad; 63°26.340′ N, 10°30.329′ E; depth 3 m; 4 Sep. 2018; M. Capa et al. leg.; stn 2018033; van Veen grab; NTNU-VM 76719 • 1 spec.; Hitra, Reitholmen; 63°37.339′ N, 9°7.762′ E; depth 38 m; 27 Jan. 2022; Åkerblå AS leg.; stn REI-3; van Veen grab; NTNU-VM 84044 • 5 specs; Ørland, Havsund; 63°47.870′ N, 9°26.236′ E; depth 35 m; 30 Oct. 2019; Åkerblå AS leg.; stn HAV-5; van Veen grab; NTNU-VM 84055 • 1 spec.; Ørland, Havsund; 63°48.073′ N, 9°26.799′ E; depth 22 m; 30 Oct. 2019; Åkerblå AS leg; stn HAV-3; van Veen grab; NTNU-VM 84053 • 6 specs; Ørland, Havsund; 63°48.091′ N, 9°26.385′ E; depth 26 m; 30 Oct. 2019; Åkerblå AS leg.; stn HAV- 4; van Veen grab; NTNU-VM 84054 . – Nordland • 1 spec.; Bodø, Brønnøyskjaeran; 67°25.242′ N, 13°54.936′ E; depth 15 m; 25 Nov. 2021; Åkerblå AS leg.; stn BRØ-REF; van Veen grab; NTNU-VM 84045 . – Troms • 2 specs; Gratangen, Follesøy; 68°41.586′ N, 17°25.972′ E; depth 34 m; 28 Jan. 2022; Åkerblå AS leg.; stn FOL-2; van Veen grab; NTNU-VM 84065 • 4 specs; Hamarøy, Jøvik; 69°8.155′ N, 17°19.840′ E; depth 20 m; 21 Oct. 2020; Åkerblå AS leg.; stn JØV-1; van Veen grab; NTNU-VM 84060 • 1 spec.; Hamarøy, Hallarøy; 69°8.820′ N, 16°51.778′ E; depth 97 m; 29 Oct. 2019; Åkerblå AS leg.; stn HAL-REF; van Veen grab; NTNU-VM 84061 • 1 spec.; Tromsø; 69°46.362′ N 19°13.869′ E; 29 Mar. 2021; Åkerblå AS leg.; stn R1-4; van Veen grab; NTNU-VM 84052 • 2 specs; Karlsøy, Dåvøy; 70°3.313′ N, 19°18.781′ E; depth 72 m; 11 Nov. 2021; Åkerblå AS leg; stn DÅV-REF; van Veen grab; NTNU-VM 84069 • 5 specs; Karlsøy, Karaneset; 70°3.586′ N, 19°18.296′ E; depth 63 m; 11 Aug. 2021; Åkerblå AS leg.; stn KAR-2; van Veen grab; NTNU-VM 84070 • 9 specs; Karlsøy, Karaneset; 70°3.734′ N, 19°18.379′ E; depth 97 m; 11 Aug. 2021; Åkerblå AS leg.; stn KAR-3; van Veen grab; NTNU-VM 84071 • 1 spec.; Karlsøy Karaneset; 70°4.132′ N, 19°18.715′ E; depth 73 m; 11 Aug. 2021; Åkerblå AS leg.; stn KAR-4; van Veen grab; NTNU-VM 84064 • 2 specs; Karlsøy, Karaneset; 70°6.109′ N, 19°35.191′ E; depth 134 m; 11 Aug. 2021; Åkerblå AS leg.; stn KAR-5; van Veen grab; NTNU-VM 84073 • 5 specs; Karlsøy, Nordnibba; 70°9.855′ N, 19°21.322′ E; depth 73 m; 11 Oct. 2021; Åkerblå AS leg.; stn NOR-REF; van Veen grab; NTNU-VM 84038 • 1 spec.; Karlsøy, Nordnibba; 70°9.993′ N, 19°22.469′ E; depth 67 m; 11 Oct. 2021; Åkerblå AS leg.; stn NOR-5; van Veen grab; NTNU-VM 84039 .

SWEDEN • 1 spec.; depth 10–20 m; 1991; stn Krugglö 91; sledge; SMNH 111893 . – Halland • 7 specs; Varberg, Värö; 57°10.000′ N, 12°1.000′ E; depth 47 m; 1984; stn VÄRV84#3; van Veen grab; SMNH 53678 • 88 specs; Varberg, Värö; 57°10.000′ N, 12°5.000′ E; depth 20 m; 1980; stn Varö spring 1980 2; van Veen grab; SMNH 9554 • 50 specs; Varberg, Värö; 57°10.000′ N, 12°1.000′ E; depth 47 m; 1978; stn Varö spring 1980 3; van Veen grab; SMNH 6453 • 30 specs; Varberg Värö; 57°10.000′ N, 12°5.000′ E; depth 20 m; 1984; stn VÄRH84#2; van Veen grab; SMNH 52794 • 100 specs; Varberg, Värö; 57°10.000′ N, 12°1.000′ E; depth 47 m; 1979; stn VÄRV79#3; van Veen grab; SMNH 8710 • 20 specs; Varberg, Värö; 57°13.000′ N, 12°1.000′ E; depth 39 m; 1984; stn VÄRH84#4; van Veen grab; SMNH 53565 • 20 specs; Varberg, Värö; 57°13.000′ N, 12°4.000′ E; depth 21 m; 1987; stn VÄRV87#1; van Veen grab; SMNH, 54728 • 50 specs; Varberg, Värö; 57°13.000′ N, 12°4.000′ E; depth 21 m; 1984; stn VÄRH84#1; van Veen grab; SMNH 52763 • 13 specs; Varberg, Värö; 57°16.000′ N, 12°5.000′ E; depth 19 m; 1981; stn VÄRH81#7; van Veen grab; SMNH, 11431 • 150 specs; Varberg, Värö; 57°16.000′ N, 12°5.000′ E; depth 19 m; 1984; stn VÄRV84#7; van Veen grab; SMNH 53617 .

UNITED KINGDOM • 10 specs; Loch Creran ; 56.523511 N, 5.355115 W; depth 25 m; 31 May 1905; stn Loch Creran 4; van Veen grab; SMNH 180569 .

Examined material with sequence data

NORWAY – Akershus • 2 specs; Asker, Saetre; 59°39.372′ N, 10°36.486′ E; depth 18–45 m; 20 Oct. 2014; stn POLYSKAG 2014/10-3; van Veen grab; ZMBN 152617 . – Oslo • 1 spec.; Oslo; 59°54.434′ N, 10°44.013′ E; depth 13 m; 18 Sep. 2018; M. Capa leg; stn 2018188; van Veen grab; NTNU-VM 76527 . – Vestfold • 1 spec.; 58°49.716′ N, 10°34.626′ E; depth 127–148 m; 17 May 2009; ZMBN leg.; stn BS48-82; sledge; ZMBN 152618 . – Agder • 1 spec.; Kristiansand, Skoltebukta; 58°9.026′ N, 8°2.060′ E; depth 8 m; 23 Aug. 2019; T. Bakken leg.; etsn. 2019060; van Veen grab; NTNU-VM 77485 . – Vestland • 12 specs; Bergen, Bergsvika; 60°19.133′ N, 5°15.317′ E; depth 48 m; 12 Sep. 2019; M. Capa leg.; stn SØR D1; van Veen grab; NTNU-VM 76741 • 1 spec.; Alver, Jibbersholmen; 60°45.052′ N, 4°53.330′ E; depth 80 m; 18 Dec. 2019; Åkerblå AS leg.; stn JIB-4; van Veen grab; NTNU-VM 84096 • 1 spec.; Fjaler, Hegnes; 61°21.470′ N, 5°17.110′ E; depth 243 m; 4 Dec. 2019; Åkerblå AS leg.; stn HEG-1; van Veen grab; NTNU-VM 84049 • 1 spec.; Sogndal, Beitveit; 62°8.171′ N, 5°19.906′ E; depth 138 m; 10 Oct. 2019; Åkerblå AS leg.; stn BEI-3; van Veen grab; NTNU-VM 84098 • 1 spec.; Øygarden, Fjell; 60°19.591′ N, 5°8.451′ E; depth 75 m; 2 Sep. 2014; ZMBN leg.; stn HB 2014.09.02 - 2; van Veen grab; ZMBN 152629 • 1 spec.; Øygarden, Sund; 60°10.080′ N, 5°0.420′ E; depth 17 m; 23 Apr. 2014; ZMBN leg.; stn HB 2014.04.24 -3; van Veen grab; ZMBN 152615 • 1 spec.; Øygarden, Sund; 60°12.046′ N, 5°2.305′ E; depth 30–60 m; 7 Sep. 2016; ZMBN leg.; stn HB 2016.09.07 -2; sledge; ZMBN 152628 • 1 spec.; Bergen, Flesland; 60°17.052′ N, 5°12.087′ E; depth 72 m; 2 Sep. 2014; ZMBN leg.; stn HB 2014.09.02 -1; van Veen grab; ZMBN 152619 • 1 spec.; Alver, Håøysundet; 60°32.984′ N, 5°13.738′ E; depth 37 m; 20 Apr. 2017; ZMBN leg.; stn HB 2017.04.20 -2; van Veen grab; ZMBN 152622 • 1 spec.; Alver, Radfjorden; 60°36.009′ N, 5°9.262′ E; depth 106m; 6 Mar. 2017; ZMBN leg.; stn HB 2017.03.06 -5; van Veen grab; ZMBN 152634 . – Møre og Romsdal • 1 spec.; Kristiansund, Or; 63°2.087′ N, 7°50.760′ E; depth 60 m; 13 Nov. 2019; Åkerblå AS leg.; stn OR-2; van Veen grab; NTNU-VM 84048 . – Trøndelag • 1 spec.; Trondheim; 63°26.308′ N, 10°23.940′ E; depth 6 m; 5 Sep. 2018; M. Capa et al. leg.; stn 2018044; van Veen grab; NTNU-VM 75547 .

Remarks

The new material agrees well with the type specimens and original and later descriptions of P. fallax ( Söderström 1920; Sigvaldadóttir & Mackie 1993). Among Northeast Atlantic species of Prionospio , P. fallax is uniquely distinguished by the presence of a prominent single dorsal crest on chaetiger 7. Although the type material was made available for examination at UPSZTY, the microscopy facilities on site were inadequate for detailed morphological study or for obtaining diagnostic photographs. Additionally, the types were not available for loan. Due to these limitations, we did not attempt a full redescription or imaging of the type material.

Some morphological features not previously described for P. fallax were observed in the present study in the non-type material. Some large individuals had pinnules present almost to the tip of branchiae ( Fig. 8A), rather than absent on long distal part of branchiae ( Fig. 8B), as described by Söderström (1920) and Sigvaldadóttir & Mackie (1993). Large specimens had notopodial postchaetal lamellae of chaetiger 6 and/ or chaetiger 8 basally extending halfway across the dorsum; however, these extensions never met middorsally to form transverse crests ( Fig. 8A). Dorsolateral longitudinal ciliation between chaetigers 4–7 is documented here for P. fallax for the first time. Prionospio fallax has been reported from Norway, Sweden, Scotland, and the Mediterranean Sea ( Sigvaldadóttir & Mackie 1993). We found no morphological differences between populations from northern Europe and the Mediterranean. However, it should be noted that molecular data are currently only available for specimens from Norwegian waters. Broader sampling and genetic analysis might be needed to confirm the identity of the Mediterranean populations.

Habitats and distribution

Prionospio fallax is known from Norway, Sweden, Scotland and the western Mediterranean Sea between 4 and 244 m depth.