Scalibregma hanseni

ScalIbregma hansenI n. sp.

Figures 4–6

Type locality. Norwegian continental shelf break, ‘Egga’, west of Nordland County, 68°50.42'N 13°05.22'E, 765 m.

Type material. Holotype (ZMBN 94016), MAREANO Sta. R351-355, RP, 29 Oct. 2008, complete specimen, female with eggs in body cavity, in ethanol; 5 paratypes (ZMBN 94017), same sample as holotype, in ethanol; 1 paratype (ZMBN 94018), same sample as holotype, mounted for SEM; 1 paratype (ZMBN 94019), 1 paratype (ZMBN 94021) MAREANO Sta. R351-356, RP, from type locality, 29 Oct. 2008, in ethanol; 1 paratype (ZMBN 94020), same sample as previous, mounted for SEM.

Other material. R/V ‘ Håkon Mosby ’ stations: Sta. 81.03.21.1, Lat: 63.166 Long: 0 4.816, 830 m, -0.9°C, 21 Mar. 1981, 2 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. 81.08.16.7, Lat: 62.553 Long: 0 0.981, 800 m, -0.9°C, 3 spms; Sta. 82.01.20.4, Lat: 62.495 Long: 0 2.136, 497 m, 2.2°C, 20 Jan. 1982, 1 spm; Sta. 82.01.21.2, Lat: 62.491 Long: 0 1.721, 604 m, 1.1°C, 21 Jan. 1982, 10 spms; Sta. 82.01.21.4, Lat: 62.560 Long: 0 0.981, 804 m, -0.9°C, 21 Jan. 1982, 1 spm; Sta. 82.11.27.1, Lat: 62.985 Long: 0 3.218, 804 m, - 1.0°C, 27 Nov. 1982, 11 spms; Sta. 83.06.0 2.1, Lat: 62.198 Long: -00.003, 708 m, -0.3°C, 2 June 1983, 5 spms; Sta. 83.06.0 2.1, Lat: 62.198 Long: -00.003, 708 m, -0.3°C, 2 June 1983, 5 spms; Sta. 83.06.0 3.2, Lat: 60.201 Long: -06.625, 1220 m, -0.8°C, 3 June 1983, 4 spms; Sta. 83.06.17.3, Lat: 62.593 Long: 0 1.233, 781 m, -0.9°C, 17 June 1983, 17 spms; Sta. 84.05.23.1, Lat: 62.585 Long: 0 1.793, 656 m, -0.8°C, 23 May 1984, 3 spms; Sta. 84.05.23.2, Lat: 62.590 Long: 0 1.795, 650 m, 23 May 1984, 2 spms; Sta. 84.05.23.3, Lat: 62.508 Long: 0 1.851, 576 m, -0.4°C, 23 May 1984, 4 spms; Sta. 84.05.23.5, Lat: 62.603 Long: 0 2.233, 576 m, -0.8°C, 23 May 1984, 4 spms; Sta. 84.11.21.2, Lat: 62.553 Long: 0 1.820, 625 m, -0.8°C, 21 Nov. 1984, 8 spms; Sta. 85.01.0 8.1, Lat: 62.525 Long: 0 1.443, 701 m, -0.9°C, 8 Jan. 1985, 5 spms (1 mounted for SEM); Sta. 85.01.0 8.2, Lat: 62.706 Long: 0 1.186, 897 m, -0.9°C, 8 Jan. 1985, 4 spms; Sta. 86.07.25.1, Lat: 69.023 Long: -08.410, 879 m, -0.6°C, 25 July 1986, 7 spms; Sta. 86.07.27.2, Lat: 70.810 Long: -09.728, 886 m, -0.6°C, 27 July 1986, 5 spms (1 mounted for SEM); Sta. 86.07.27.5, Lat: 70.678 Long: 0 7.631, 1243 m, -0.6°C, 27 July 1986, 1 spm; Sta. 86.08.15.5, Lat: 62.610 Long: 0 1.573, 654 m, -0.9°C, 15 Aug. 1986, 1 spm; Sta. 86.08.15.7, Lat: 62.843 Long: 0 1.431, 951 m, -0.9°C, 15 Aug. 1986, 1 spm; Sta. 86.08.17.5, Lat: 62.996 Long: 0 1.140, 1143 m, -0.9°C, 17 Aug. 1986, 2 spms; Sta. 86.08.17.6, Lat: 62.691 Long: 0 1.756, 750 m, -0.9°C, 17 Aug. 1986, 16 spms. MAREANO stations: Sta. R351-355, RP, Lat: 68.84033 Long: 13.08700, 765 m, 29 Oct. 2008, 9 spms; Sta. R351-356, 68.84033N 13.08700E, 765 m, 29 Oct. 2008, 8 spms; Sta. R416-386, Lat: 71.93600 Long: 15.53133, 777 m, 22 April 2009, 10 spms; Sta. R464-143, Lat: 71.33700 Long: 16.51324, 853 m, -0.48°C, 25 Sept. 2009, 2 spms. Environmental monitoring stations: Sta. OL-01, Lat: 63.48446 Long: 0 5.36994, 837 m, 17 June 2004, 2 spms; Sta. OL-04, Lat: 63.51289 Long: 0 5.37823, 858 m, 18 June 2004, 1 spm; Sta. OL-06, Lat: 63.52350 Long: 0 5.37058, 870 m, 18 June 2004, 2 spms; Sta. OL-08, Lat: 63.53813 Long: 0 5.38181, 852 m, 18 June 2004, 1 spm; Sta. OL-13, Lat: 63.56073 Long: 0 5.39664, 883 m, 19 June 2004, 3 spm; Sta. V-07, Lat: 63.50149 Long: 0 5.65205, 591 m, 1 June 1991, 6 spms; Sta. V-09, Lat: 65.00138 Long: 0 5.00019, 757 m, 1 June 1998, 3 spms.

Description. Length of entire specimens 7–10 mm for 35–41 segments, width up to 1.9 mm. Body arenicoliform, anterior part swollen, posterior region tapered (Fig. 4). Holotype 9.5 mm long for 38 chaetigers, maximum width 1.8 mm, body swollen at chaetigers 5–13.

Prostomium T-shaped, with two long digitiform processes directed laterally or anterolaterally (Fig. 5 A). Eyes lacking. Peristomium achaetous, dorsally well-developed with two rings and partly covering posterior part of prostomium, ventrally narrow. Mouth ventral, rounded oval, with broad anterior and posterior lips. Proboscis occasionally everted, simple or folded with undulating rim.

Peristomium and first chaetiger of about same width as posterior body. Following chaetigers gradually increasing in width, body swollen from chaetigers 5–7 to chaetigers 13–16 (Fig. 4 A). Anterior segments with four annuli, segments posterior to swollen part with 5–6 annuli. Body surface tessellate. Ventral side with medial longitudinal furrow with rounded borders. Furrow with row of squarish epidermal pads (‘ventral shields’), one pad per segment, pads mostly indistinct in swollen region and posterior part of body (Fig. 4 B). Pygidium rounded, with ventral furrow and about ten short dorsal and lateral lobes (Fig. 5 B). Anal cirri filiform, somewhat thicker distally than proximally, easily detached (Fig. 4 F). Number of cirri not ascertained, up to five observed.

Three pairs of branchiae, situated on chaetigers 3–5. Branchiae mostly simple, consisting of 1–4 simple or partly subdivided filaments, arising posterior to notopodia (Fig. 5 C, D). Branchiae usually increasing in size from anterior to posterior. Parapodia in anterior third of body small, inconspicuous, with low, evenly rounded prechaetal lobes in both rami (Fig. 4 C). Parapodia gradually developing from chaetigers 10–12, becoming well-developed from about chaetigers 14–16 (Fig. 5 E, 4D). Dorsal cirri appearing from chaetigers 13–14, short triangular on most of body, becoming lanceolate in far posterior chaetigers. Ventral cirri appearing from chaetigers 14–16, triangular in most anterior chaetigers, rapidly becoming more pointed to lanceolate in following chaetigers (Fig. 5 F). Dorsal and ventral cirri with internal glandular structure, yellow coloured in preserved specimens (Fig. 4 E). Papillate interramal sense organ from about chaetiger 15 to posterior end (Fig. 5 G–H).

All chaetigers with slender capillaries in both rami. First and second chaetiger in addition with gently curved, thin, blunt-tipped spines anterior to capillaries (Fig. 6 A–C), first chaetiger with 4–6 spines in both rami, second chaetiger with 6–8 somewhat longer spines. Notopodial spines located in a slightly curved vertical row in lower part of chaetal fascicle, neuropodial spines in a vertical row anterior to capillaries. All following chaetigers with furcate chaetae in both rami, located in a vertical row anterior to capillaries. Chaetiger 3 with 7–8 furcate chaetae, further back 8–12 (Fig. 6 D–E). Tines of furcate chaetae of unequal lengths (ratio 1.15:1.35), longest tine with thin whip-shaped distal part, inner margin of tines with strong comb of teeth (Fig. 6 E–F). Capillaries hirsute, blunt spines and furcate chaetae with even surface structure (Fig. 6).

Colour. Alcohol-preserved specimens light grey-brownish. Dorsal and ventral cirri usually bright yellow to brownish from colouring of internal glandular structure. Some specimens with transverse bands of light brownish epidermal pads on swollen part of body. Holotype with yellow transversal pigment bands dorsally on chaetigers 3– 5, dorsal and ventral cirri in posterior body yellow.

Reproduction. Ovigerous females observed in samples from continental shelf break off Nordland County at 68° N, 765 m, October 2008. Diameter of eggs up to 180 µm. Holotype with eggs 120–140 µm in diameter.

Distribution. The species has been found on the continental slope in the eastern Norwegian Sea, from deep areas around Jan Mayen, and from a single record on the Wyville-Thomspon Ridge at 1220 m depth (Fig. 7 C). The depth range is 497–1243 m. Most samples are from the upper slope (600–800 m), coinciding with a transition zone from temperate North Atlantic water to cold Norwegian Sea water, with temperatures fluctuating around 0°C.

Etymology. This species is named after Gerhard Armauer Hansen for his contribution on polychaetes in the Norwegian Sea. In his treatment of the polychaetes from the Norwegian North-Atlantic Expedition 1876–1878, he described Pseudoscalibregma parvum and provided a description of Scalibregma abyssorum, which may have included material of the present species (Hansen 1879, 1882).

Remarks. Presently six species are considered valid in the genus Scalibregma. Four species are found in NE Atlantic and Arctic waters, viz. S. inflatum, S. robustum Zachs, 1925, S. wireni Furreg, 1925, and S. celticum Mackie, 1991, and two species are found in US coastal waters: S. stenocerum (Bertelsen & Weston, 1980), and S. californicum Blake, 2000. Scalibregma hanseni n. sp shares with S. stenocerum the possession of three pairs of branchiae (on chaetigers 3–5), whereas all other species have four pairs of branchiae. Scalibregma hanseni n. sp. differs from S. stenocerum by having short rather than long, slender prostomial horns, by lacking eyes, and by having rather simple branchiae with few branches in contrast to bushy, multibranched branchiae.

Scalibregma hanseni n. sp., S. stenocerum and S. celticum all have smooth blunt spines on chaetigers 1 and 2. Mackie (1991) discussed the taxonomic relevance of spines on the most anterior chaetigers and their possible homology with furcate chaetae in more posterior chaetigers.