Pseudoscalibregma parvum Hansen 1879

PseudoscalIbregma parvum (Hansen, 1879)

Figures 1–3

Scalibregma parvum Hansen, 1879: 7 –8, pl. V, figs 7–14.—1882: 35–36.

Eumenia longisetosa Théel, 1879: 49 –51, pl. III, figs 45–47, pl. IV, fig. 48.

Pseudoscalibregma longisetosum.— Furreg 1925: 170 –176, figs S–X.

Pseudoscalibregma parvum.— Ashworth 1901: 296.− Støp-Bowitz 1945: 72 –75, fig. 3.—1948: 27–29, fig. 9.— Jirkov 2001: 368.— Bakken et al. 2010: 12.

Type locality. The Norwegian Sea, off the coast of western Norway at 63°10’N 4°0’E, 763 m, The Norwegian North-Atlantic Expedition Sta. 31 (lectotype designated here).

Type material. Pseudoscalibregma parvum: Lectotype (ZMBN 94015) and 3 paralectotypes (ZMBN 2275). Paralectotypes from two different localities, Norwegian North-Atlantic Expedition Sta. 31 (type locality) and Sta. 18, 62°44'N 1°48'E, 753 m (see “Remarks” for details). Eumenia longisetosa Theel, 1879 (all syntypes): SMNH- 118416, 4 spms, Kara Sea, Russia, 5 Aug 1875, 20 m, sand, No 150, 70°40'N 64°17'E, Leg N. Semlja Exp. 1875; SMNH-118413, 5 spms, Kara Sea, Russia, 3 Aug 1875, NE of Jugar Scharr, 218 m, clay, Leg N. Semlja Exp. 1875; SMNH-118411, 5 spms, Kara Sea, Russia, No 147, 164 m, mud, 71°05'N 61°20'E, Leg N. Semlja Exp. 1875; SMNH-118412, 3 spms, Kara Sea, Russia, 4 Aug 1875, No 147, 71°05'N 61°20'E, 164 m, clay, Leg N. Semlja Exp. 1875; SMNH-118414, 1 spm, Novaja Zemlja, Kara Sea, Russia, No 148, 4 Aug 1875, 127 m, 71°40'N 63°50'E, Leg N. Semlja Exp. 1875; SMNH-118415, 2 spms, Kara Sea, Russia, 31 Aug 1875, No 186, 109 m, 73°34'N 57°56'E, Leg N. Semlja Exp. 1875; SMNH-118409, 1 spm, Matoschkin Scharr, E of Rossman Station, Russia, No 12, 73– 91 m, muddy stones, 4 Aug 1876, Leg Nordenskiolds Exp. 1876.

Other material. Swedish Arctic Expedition 1899: SMNH-126668, 9 spms, Hurry's Inlet, Scoresby Sound, eastern Greenland, No 33, 4 Aug 1899, 70°43'N 22°29'W, 70 m; SMNH-126665, 5 spms, eastern Greenland, No 18, 4 July, No 18, 4 July 1899, 74°55'N 17°59'W, 350 m, ooze, sand and pebbles; SMNH-126664, 4 spms, Jan Mayen, 24 June 1899, No 17, 71°12'N 08°28'W, 1275 m, grey clay; SMNH-126666, 11 spms, Cap Darry, eastern Greenland, 24 July 1899, No 25, 72°28'N 21°48'W, 180 m, mud with stones;. SMNH-126667, 3 spms, about 1 km W of Murray's Inlet, eastern Greenland, 28 July 1899, No 28, 71°33'N 21°44'W, 200 m, mud with some stones. R/ V ‘ H. Mosby ‘ stations: Sta. 81.03.21.1, Lat: 63.166 Long: 0 4.816, 830 m, -0.9°C, 21 Mar. 1981, 12 spms; Sta.

81.03.22.1, Lat: 63.285 Long: 0 4.413, 1260 m, -0.9°C, 22 Mar. 1981, 8 spms; Sta. 81.06.0 4.4, Lat: 66.983 Long: 0 4.270, 1380 m, -0.9°C, 4 June 1981, 3 spms; Sta. 81.06.0 6.3, Lat: 65.686 Long: 0 5.633, 602 m, 0.3°C, 6 June 1981, 1 spm; Sta. 81.06.0 6.7, Lat: 65.716 Long: 0 5.238, 794 m, -0.9°C, 6 June 1981, 23 spms; Sta. 81.06.0 6.8, Lat: 65.666N Long: 0 4.815, 996 m, -1.0°C, 6 June 1981, 1 spm; Sta. 81.06.0 7.1, Lat: 65.696 Long: 0 4.381, 1211 m, - 1.0°C, 7 June 1981, 1 spm; Sta. 81.08.13.2, Lat: 63.423 Long: 0 4.090, 1288 m, -0.9°C, 13 Aug. 1981, 5 spms; Sta. 81.08.15.5, Lat:. 63.198 Long: 0 0.693, 1494 m, -0.9°C, 15 Aug. 1981, 2 spms; Sta. 81.08.15.6, Lat: 63.201 Long: 0 0.693, 1501 m, -1.0°C, 15 Aug. 1981, 1 spm; Sta. 81.08.16.3, Lat: 62.800 Long: 0 1.043, 1009, -1.0°C, 16 Aug. 1981, 5 spms; Sta. 81.08.16.7, Lat: 62.553 Long: 0 0.981, 800 m, -0.9°C, 16 Aug. 1981, 18 spms; Sta. 82.01.21.2, Lat: 62.491 Long: 0 1.721, 604 m, 1.1°C, 21 Jan. 1982, 6 spms; Sta. 82.01.21.4, Lat: 62.560 Long: 0 0.981, 804 m, - 0.9°C, 21 Jan. 1982, 10 spms; Sta. 82.01.21.6, Lat: 62.803 Long: 0 1.088, 984 m, -0.9°C, 21 Jan. 1982, 2 spms; Sta. 82.08.15.1, Lat: 63.048 Long: 0 0.808, 1286 m, -1.0°C, 15 Aug. 1982, 6 spms; Sta. 82.08.19.1, Lat: 66.626 Long: 0 2.515, 1626 m, -0.9°C, 19 Aug. 1982, 1 spm; Sta. 82.08.23.1, Lat: 63.213 Long: 0 3.121, 1003 m, -1.0°C, 23 Aug. 1982, 12 spms; Sta. 82.11.26.1, Lat: 63.178 Long: 0 2.765, 1030 m, -1.0°C, 26 Nov. 1982, 8 spms; Sta. 82.11.27.1, Lat: 62.985 Long: 0 3.218, 804 m, -1.0°C, 27 Nov. 1982, 20 spms; Sta. 83.06.0 2.1, Lat: 62.198 Long: -00.003, 708 m, -0.3°C, 2 June 1983, 4 spms; Sta. 83.06.0 3.1, Lat: 61.343 Long: -03.185, 1338 m, -0.7°C, 3 June 1983, 2 spms; Sta. 83.06.0 3.2, Lat: 60.201 Long: -06.625, 1220 m, -0.8°C, 3 June 1983, 1 spm; Sta. 83.06.0 7.2, Lat: 64.435 Long: -11.170, 400 m, -0.2°C, 7 June 1983, 1 spm; Sta. 83.06.0 8.1, Lat: 65.168 Long: -09.493, 784 m, -0.6°C, 2 spms; Sta. 83.06.0 8.2, Lat: 65.460 Long: -07.588, 1626 m, -0.9°C, 8 June 1983, 7 spms; Sta. 83.06.17.3, Lat: 62.593 Long: 0 1.233, 781 m, -0.9°C, 17 June 1983, 108 spms; Sta. 84.03.15.2, Lat: 68.891 Long: -14.238, 1588 m, -0.9°C, 15 Mars 1984, 2 spms; Sta. 84.05.23.1, Lat: 62.585 Long: 0 1.793, 656 m, -0.8°C, 23 May 1984, 80 spms; Sta. 84.05.23.2, Lat: 62.590 Long: 0 1.795, 650 m, 23 May 1984, 4 spms; Sta. 84.05.23.3, Lat: 62.508 Long: 0 1.851, 576 m, -0.4°C, 23 May 1984, 1 spm; Sta. 84.05.23.5, Lat: 62.603 Long: 0 2.233, 576 m, -0.8°C, 23 May 1984, 6 spms; Sta. 84.11.20.2, Lat: 63.133 Long: 0 1.895, 1087 m, -0.9°C, 20 Nov. 1984, 28 spms; Sta. 84.11.21.1, Lat: 62.791 Long: 0 1.836, 811 m, -0.9°C, 21 Nov. 1984, 3 spms; Sta. 84.11.21.2, Lat: 62.553 Long: 0 1.820, 625 m, - 0.8°C, 21 Nov. 1984, 53 spms; Sta. 85.01.0 8.1, Lat: 62.525 Long: 0 1.443, 701 m, -0.9°C, 8 Jan. 1985, 75 spms; Sta. 85.01.0 8.2, Lat: 62.706 Long: 0 1.186, 897 m, -0.9°C, 8 Jan. 1985, 34 spms; Sta. 85.01.0 8.3, Lat: 62.911 Long: 0 0.928, 1112 m, -0.9°C, 8 Jan. 1985, 14 spms; Sta. 85.01.0 8.4, Lat: 63.291 Long: 0 0.471, 1698 m, -0.9°C, 8 Jan. 1985, 1 spm; Sta. 85.01.12.2, Lat: 63.166 Long: 0 0.643, 1489 m, -0.9°C, 12 Jan. 1985, 8 spms; Sta. 85.01.12.3, Lat: 63.048 Long: 0 0.796, 1293 m, -0.9°C, 12 Jan. 1985, 12 spms; Sta. 86.06.12.2, Lat: 63.638 Long: -07.025, 1533 m, -0.9°C, 12 June 1986, 2 spms; Sta. 86.06.13.1, Lat: 63.218 Long: -07.031, 1261 m, -0.8°C, 13 June 1986, 2 spms; Sta. 86.06.13.4, Lat: 63.045 Long: -07.028, 1022 m, -0.8°C, 13 June 1986, 2 spms; Sta. 86.06.13.5, Lat: 62.948 Long: -07.002, 748 m, -0.6°C, 13 June 1986, 1 spm; Sta. 86.06.16.1, Lat: 62.855 Long: -05.698, 750 m, - 0.4°C, 16 June 1986, 6 spms; Sta. 86.07.25.1, Lat: 69.023 Long: -08.410, 879 m, -0.6°C, 25 July 1986, 464 spms; Sta. 86.07.27.2, Lat: 70.810 Long: -09.728, 886 m, -0.6°C, 27 July 1986, 234 spms; Sta. 86.07.27.5, Lat: 70.678 Long: -07.631, 1243 m, -0.6°C, 27 July 1986, 9 spms; Sta. 86.07.31.1, Lat: 63.103 Long: -00.841, 1751 m, -0.9°C, 31 July 1986, 8 spms; Sta. 86.08.15.5, Lat: 62.610 Long: 0 1.573, 654 m, -0.9°C, 15 Aug. 1986, 44 spms; Sta. 86.08.15.7, Lat: 62.843 Long: 0 1.431, 951 m, -0.9°C, 15 Aug. 1986, 8 spms; Sta. 86.08.16.2, Lat: 63.118 Long: 0 0.851, 1342 m, -0.9°C, 16 Aug. 1986, 9 spms; Sta. 86.08.17.3, Lat: 63.368 Long: 0 0.551, 1750 m, -0.9°C, 17 Aug. 1986, 2 spms; Sta. 86.08.17.5, Lat: 62.996 Long: 0 1.140, 1143 m, -0.9°C, 17 Aug. 1986, 11 spms; Sta. 86.08.17.6, Lat: 62.691 Long: 0 1.756, 750 m, -0.9°C, 17 Aug. 1986, 132 spms; Sta. 87.06.13.1, Lat: 69.978 Long: 12.545, 1832 m, -0.9°C, 13 June 1987, 1 spm. R/V ‘ Jan Mayen ‘ stations: Sta. 808-99, Lat: 70.9768 Long: - 0 8.7735, 109 m, 14 Sept. 1999, 1 spm; Sta. 813-99, Lat: 71.1068 Long: -09.5877, 514 m, 15 Sept. 1999, 22 spms; Sta. 834-99, Lat: 70.7512 Long: -07.9623, 771 m, 16 Sept. 1999, 104 spms; Sta. 848-99, Lat: 70.6478 Long: - 0 9.3722, 599 m, 17 Sept. 1999, 7 spms; Sta. 850-99, Lat: 70.6032 Long: -09.3453, 313 m, 17 Sept. 1999, 4 spms. R/V ‘ Meteor ‘ station: Sta. M414/90, Lat: 74.9667 Long: 14.0283, 1748 m, -1.1°C, 17 July 1990, 2 spms. R/V ‘ G. O. Sars ‘ CGB stations: Sta. Dive-07, Lat: 71.2998 Long: -5.7800, 616 m, June 2006, 1 spm; Sta. Dive-12, Lat: 71.2997 Long: -5.7820, 616 m, June 2006, 2 spms. MAREANO stations: Sta. R405-59, RP, Lat: 72.14017 Long: 15.34583, 899 m, April 2009, 10 spms (3 mounted for SEM); Sta. R754-132, RP, Lat: 67.80459 Long: 9.68544, 823 m, 22 Sept. 2011, 21 spms; Sta. R882-12, RP, Lat: 67.28434 Long: 8.13304, 1117 m, 8 May 2012, 5 spms. Environmental monitoring stations: Sta. OL-01, Lat: 63.48446 Long: 0 5.36994, 837 m, 17 June 2004, 7 spms; Sta. OL-02, Lat: 63.49451 Long: 0 5.41986, 822 m, 17 June 2004, 5 spms; Sta. OL-03, Lat: 63.50035 Long: 0 5.36968, 867 m, 17 June 2004, 8 spms; Sta. OL-04, Lat: 63.51289 Long: 0 5.37823, 858 m, 18 June 2004, 6 spms; Sta. OL- 0 5, Lat: 63.50675 Long: 0 5.40527, 828 m, 17 June 2004, 3 spms; Sta. OL-06, Lat: 63.52350 Long: 0 5.37058, 870 m, 18 June 2004, 5 spms; Sta. OL-07, Lat: 63.52469 Long: 0 5.40486, 843 m, 18 June 2004, 2 spms; Sta. OL-08, Lat: 63.53813 Long: 0 5.38181, 852 m, 18 June 2004, 8 spms; Sta. OL-09, Lat: 63.53583 Long: 0 5.40537, 854 m, 18 June 2004, 5 spms; Sta. OL-10, Lat: 63.53050 Long: 0 5.43927, 810 m, 18 June 2004, 3 spms; Sta. OL-11, Lat: 63.55031 Long: 0 5.42835, 851 m, 18 June 2004, 11 spms; Sta. OL-12, Lat: 63.55516 Long: 0 5.36859, 901 m, 19 June 2004, 6 spms (2 mounted for SEM); Sta. OL-13, Lat: 63.56073 Long: 0 5.39664, 883 m, 19 June 2004, 1 spm; Sta. V-02, Lat: 63.50148 Long: 0 2.33322, 1325 m, 1 June 1998, 1 spm; Sta. V-06, Lat: 63.50074 Long: 0 5.33366, 913 m, 1 June 1998, 5 spms; Sta. V-09, Lat: 65.00138 Long: 0 5.00019, 757 m, 1 June 1998, 6 spms; Sta. V-16, Lat: 67.00162 Long: 0 7.33367, 1174 m, 1 June 1998, 2 spms.

Redescription. Lectotype complete specimen with everted proboscis, anterior end swollen in chaetigers 2–8, 13 mm body length for 32 chaetigers (Fig. 1 B). Paralectotypes three complete specimens with some damage, measuring 11 mm for 31 chaetigers, 14 mm for 34 chaetigers, and 16 mm for 34 chaetigers, respectively. Among the original material is also one anterior fragment with 6 chaetigers, one mid-body fragment, and two posterior parts.

Length of complete specimens 4–35 mm for 29–36 chaetigers. Body elongated, tapering posteriorly. Preserved specimens usually swollen in anterior chaetigers (Figs 1, 2 A–B).

Prostomium T-shaped, squarish with a pair of prominent horns projecting anterolaterally (Fig. 2 A, C). Nuchal slits on either side of prostomium, eversible nuchal organs observed in a few specimens. Peristomium achaetous, narrow dorsally, expanding laterally to a broad ring ventrally. Mouth ventral, peristomium and first chaetiger fused. Proboscis a large smooth sac, occasionally everted (Figs 1 B, 2D).

Dorsal body surface with rectangular pads (Fig. 2 A). Dorsal body surface with secondary annulations arranged as a double row of pads dorsal to notopodia, in addition an intermediate annulation between chaetigers; annulations similar throughout, smoothed out but visible in swollen area (Fig. 2 A). Ventrally body surface with a longitudinal midventral furrow, midventrally with a prominent longitudinal row of rectangular pads, most prominent in anterior half of body (Fig. 2 B). Pygidium rounded with a dorso-ventral indentation (Fig. 2 E), and smooth folds on the rim. Pygidial cirri absent.

Parapodia on anterior part of body inconspicuous, with noto- and neuropodium well separated. In anterior chaetigers prechaetal lobe present in noto- and neuropodia, on chaetiger 1–2 prechaetal lobe barely visible (Fig. 2 F), evident from chaetiger 3–4. Parapodia gradually becoming more developed from chaetiger 12 (Figs 1, 2 A). Notopodium rounded in first few chaetigers from 12 (Fig. 2 G), becoming more produced posteriorly (Figs 1 D, 2H). Neuropodium rounded from chaetiger 12, becoming increasingly produced posteriorly (Figs 1 D, 2H). Noto- and neuropodium more or less equal in size. Dorsal and ventral cirri present from chaetiger 12. Dorsal cirri rounded knoblike, shorter than notopodium from chaetiger 12 (Fig. 2 G), becoming as long as notopodium posteriorly (Fig. 1 D). Ventral cirri barely visible on chaetigers 12–13, appearing as a low brim from chaetiger 14, then becoming increasingly rounded to elliptical posteriorly, as long as or slightly longer than neuropodium from chaetigers 20–25 (Figs 1 D, 2H). Interramal papilla present, knoblike (Fig. 1 D).

Chaetae include hirsute slender capillaries in noto- and neuropodia in all chaetigers (Fig. 3). Chaetiger 1 with one row of small pointed spines with bifurcate tips (Fig. 3 A–B) placed anterior to capillaries in both noto- (Fig. 3 A) and neuropodia (Fig. 3 D). Furcate chatae present from chaetiger 2 in both notopodia and neuropodia, having unequal tines in anterior chaetigers (Fig. 3 E–F), approaching more or less equal length in posteriormost chaetigers (Fig. 3 G), with dentation on inner side of tines (Fig. 3 F–H). Furcate chaetae occasionally found in chaetiger 1 (Fig 3 C) in both noto- and neuropodia, (not observed in all specimens). Chaetae numerous and long, organised in rows with one anterior row of furcate chaetae followed by 3–4 rows of capillaries. Chaetae most numerous in anterior chaetigers, length of chaetae subject to variation over specimens.

Reproduction. Several ovigerous females observed in January (R/V “ H. Mosby ” Sta. 85.01.08.1). Diameter of eggs up to 200 µm.

Remarks. The original material used by Hansen (1879) to describe P. p a r v u m from stations 18 and 31 from The Norwegian North-Atlantic Expedition 1876–78 were found in one vial (ZMBN 2275). The material consists of 4 complete specimens, of which 3 are damaged. In the original description Hansen stated that one specimen with damage to the mid-body was from Sta. 18, which is easy to identify among the specimens. Hence, the remaining specimens are from Sta. 31. An undamaged specimen agrees with the original description and illustration and is selected as the

lectotype; the remaining 3 specimens thereby becoming paralectotypes. The two stations where the original material was collected were relatively close to the shelf break in the Norwegian Sea at 753 m (Sta. 18) and 763 m (Sta. 31) depth. Both stations were reported to have a water temperature at the bottom of -1 °C (Hansen 1882). By selecting a lectotype from Sta. 31, the type locality is fixed to this position.

Small pointed spines were observed on chaetiger 1; in most cases with a bifurcated tip (Fig. 3 B). The spines are similar to those described in Scalibregma inflatum (Mackie 1991) and Pseudoscalibregma orientalis (Imajima 2009). The observation of small spines on chaetiger 1 in two species of Pseudoscalibregma suggests that this represents a character that may be found in other species in this genus as well.

The number of chaetigers is generally stable. The majority of specimens have 33–34 chaetigers, largely irrespective of body length. The observed range is 29–36 chaetigers in specimens measuring from 4 mm to 35 mm in body length.

There are presently six valid species in Pseudoscalibregma, of which P. parvum is the only species in the Nordic Seas and the North Atlantic. Pseudoscalibregma parvum is most similar to P. orientalis Imajima, 2009 from Japan, but is distinguished by having a smooth proboscis, which is papillated in P. orientalis, by having short dorsal and ventral cirri, which are very long in P. orientalis, and by having parapodial lobes and cirri present from chaetiger 12, in contrast to chaetiger 14 in P. orientalis. Pseudoscalibregma papilia Schüller, 2008 possesses very large inflated cirri in posterior parapodia (Schüller 2008), as does P. bransfieldium (Hartman, 1967) (Blake 1981). In P. usarpium Blake, 1981 dorsal and ventral cirri commence on chaetiger 12, as in P. parvum, but P. usarpium differs from all other species of Pseudoscalibregma in the shape of the prostomium and by possessing papillae on the dorsum (Blake 1981).

Théel (1879) gave a rather detailed description of Eumenia longisetosa based on specimens from six stations at Novaja Zemlja and in the Kara Sea, Russia. Furreg (1925) extended the species description (as Pseudoscalibregma longisetosum) based on the original material and specimens from several other Arctic localities. He also discussed P. parvum and considered Hansen’s description to represent young specimens of P. longisetosum. Later, Støp- Bowitz (1945) confirmed the synonymy of the species, but indicated that Hansen’s name was published first and took priority. There is no indication that Støp-Bowitz actually studied Théel’s specimens. In the present study the available material from Théel's description was examined. None of the vials is labelled as type material or in any way indicated as such. There are some discrepancies in positions and depths as well as station numbers compared to the station list in the original description, but the specimens obviously represent those used by Théel for his description. No morphological differences between Théel's specimens and Hansen's specimens were found. Hence, the two names must be regarded as synonymous.

The descriptions of Scalibregma parvum and Eumenia longisetosa were both published in 1879. Støp-Bowitz (1945) argued that Hansen’s name was the oldest by referring to a citation of Hansen’s work in Théel (1879, p. 9: synonymy list for Polynoe imbricata) with the year 1877 or 1878 and indicated as a separate offprint. The case is not fully clear, but Hansen's name has been used consistently in the literature following Støp-Bowitz (1945). To provide stability we suggest that this should be continued.

Distribution. Pseudoscalibregma parvum has been recorded from East Greenland, Jan Mayen, Spitsbergen, Norwegian Sea and Kara Sea, in depths from 20 to 1715 m (this study; Furreg 1925; Støp-Bowitz 1948; Jirkov 2001; Bakken et al. 2010). The shallowest records are all Arctic, from East Greenland and the Kara Sea. On the shelf around the island of Jan Mayen some shallow records, from 109 m, are from an area with mixed North Atlantic and Arctic water masses with temperatures down to below 0°C (Bakken et al. 2010). In the Norwegian Sea there are a few records in shelf areas, but most records are from 600 m and deeper, where water temperatures are below 0°C (Fig. 7 A).