Chaetozone setosa Malmgren, 1867

Grosse, Mael, Capa, Maria & Bakken, Torkild, 2021, Describing the hidden species diversity of Chaetozone (Annelida, Cirratulidae) in the Norwegian Sea using morphological and molecular diagnostics, ZooKeys 1039, pp. 139-176 : 139

Chaetozone setosa Malmgren, 1867 Figures 3 , 4

Chaetozone setosa Malmgren, 1867: 96, Pl. 14, fig. 84 (in part); Petersen 1999: 111; Chambers 2000: 589-591, fig. 1 (in part); Blake 2015: 504-507, figs 1, 2.

Chaetozone sp. 8 Grosse et al. 2020: fig. 4.

Type locality.

Isfjord, Svalbard, Norway, 55 m depth.

Material examined.

Lectotype: Svalbard • 1 ind.; Isfjord ; 06 Jun. 1864; 55 m; SMNH 1493-03 . Paralectotypes: Svalbard • 172 ind.; same data as for holotype; SMNH 1493-04-175 . Other material examined. Svalbard • 7 ind.; 78.14872°N, 13.12559°E; 13 May 2015; 243 m; ZMBN125766-125769, 125837-125838, 129637; • 2 ind.; 79.55130°N, 11.22970°E; 30 Aug. 2007; 91 m; ZMBN125815-125816 • 2 ind.; 78.32855°N, 15.14712°E; 07 May 2015; 266 m; ZMBN125811, ZMBN125813 • 2 ind.; 79.70829°N, 18.17362°E; 10 May 2015; 407 m; ZMBN125817-125818 • 1 ind.; 79.68089°N, 11.13989°E; 09 May 2015; 180 m; ZMBN125770 • 1 ind.; 79.58854°N, 18.63483°E; 10 May 2015; 242 m; ZMBN125812. - Barents Sea • 1 ind.; 71.61528°N, 32.99719°E; 9 Aug. 2013; 305 m; ZMBN125764 .

Diagnosis.

Peristomium with two large distinct annulations and dorsal crest; dorsal tentacles on posterior margin of peristomium; first pair of branchiae on distinct segment 1 (achaetous); posterior segments developed in full cinctures with up to 20-26 spines per parapodia (Figs 3 , 4 ) (based on Blake 2015).

Molecular diagnosis.

COI: 220: G. 28S: 545-546: AC (based on 36 COI sequences and 19 28S sequences).

Distribution.

Barents Sea, Svalbard, White Sea, ~ 80-400 m depth.

Remarks.

A lectotype (Fig. 3A ) and 172 paralectotypes from Svalbard were designated by Petersen (1999), from which a thorough redescription and illustrations were provided by Blake (2015). As many early described polychaete species, C. setosa has been reported from all around the world ( Chambers 2000; Oug et al. 2014), before being restricted to the Arctic and subarctic areas in northern Europe ( Blake 2015), which corresponds to the area covered by Malmgren’s type series: Spitsbergen (Svalbard), Finnmark (northern Norway) and Bohüslan (western Sweden). Specimens were recently collected from the type locality in Svalbard, as well as other areas along Northern Europe, including from the localities given in Malmgren. Genetic analyses revealed the presence of two distinct, yet morphologically identical species (Fig. 1 ): one present in Svalbard, the Barents Sea, and the White Sea (Fig. 1 ; Chaetozone sp. 8), and the other present in the Norwegian Sea, the North Sea, and the Skagerrak (Fig. 1 ; Chaetozone sp. 7) ( Grosse et al. 2020). The former species included specimens collected at the type locality of C. setosa , consequently interpreted as members of the type species of Chaetozone . The other one is described herein and named C. pseudosetosa sp. nov. This species is morphologically identical to Chaetozone pseudosetosa sp. nov., described below. Methylene blue stains the peristomium with transversal bands of varying intensity, as well as anterior segments and posterior cinctures also with transversal bands, mostly ventrally ( Blake 2015). Chaetozone pseudosetosa sp. nov. shows a similar pattern. Genetic distance in the COI marker between Chaetozone setosa and other congeners in the area mostly ranges from 20% to 25%, except for a minimum of 8% divergence with C. pseudosetosa sp. nov. (Table 2 ).

Figures

Figure 1. Cladogram of the different species present in Norway, after Grosse et al. (2020). The species treated in this paper are highlighted in grey.

Figure 3. Chaetozone setosa A lectotype SMNH 1493 - 03, in lateral view B paralectotype SMNH 1493 - 04 - 175, anterior end in lateral view, stained with Shirlastain A C paralectotype SMNH 1493 - 04 - 175, cross section of modified posterior segments. Abbreviations: br, branchiae; Ch, chaetiger; dCr, dorsal crest; dT, dorsal tentacle; per, peristomium; pr, prostomium; Seg, segment.

Figure 4. Chaetozone setosa A ZMBN 125817, SEM of anterior end in lateral view B ZMBN 125768, SEM of anterior neuropodia in lateral view C ZMBN 125817, SEM of nuchal organ, specimen D SEM of posterior cinctures in lateral view, specimen ZMBN 125817 E ZMBN 125817, SEM of neuropodial spine F ZMBN 129637, SEM of anterior end in dorsal view. Abbreviations: br, branchiae; Ch, chaetiger; dCr, dorsal crest; dT, dorsal tentacle; per, peristomium; pr, prostomium; Seg, segment.