Chaetozone, Grosse & Capa & Bakken, 2021

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 sp. 2 and sp. 4 Figures 14

Chaetozone sp. 2 Grosse et al. 2020: fig. 4.

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

Material examined.

Chaetozone sp. 2: Norwegian Sea • 1 ind.; 61.42736°N, 7.47479°E; 18 Nov. 2012; 332 m; ZMBN125800 • 1; 62.48183°N, 4.46550°E; 10 Mar. 2012; 211 m; ZMBN125823 • 1 ind.; 61.0501°N, 5.40055°E; 03 May 2017; 1236 m; ZMBN117820 • 1 ind.; 62.482°N, 4.466°E; 03 Oct. 2012; 213 m ZMBN94537 • 1 ind.; 61.11299°N, 5.14124°E; 22 Jul. 2012; 354 m; NTNU-VM74503. Chaetozone sp. 4: Norwegian Sea • 3 ind.; 61.42736°N, 7.47479°E; 18 Nov. 2012; 332 m; ZMBN125796-125798 • 1 ind.; 61.21307°N, 5.03809°E; 14 Jul. 2015; 379 m; ZMBN125776 • 1 ind.; 64.804°N, 10.111°E; 08 Oct. 2013; 378 m; ZMBN94483 • 1 ind.; 62.06827°N, 5.03811°E; 20 Jul. 2012; 334 m; ZMBN125781 • 2 ind.; 61.11299°N, 5.14124°E; 22 Jul. 2012; 360 m; NTNU-VM74500, 74507.

Comparative material.

Chaetozone jubata : Paratypes: Faroe-Shetland channel • 2 ind.; 61.5.57°N, 2.4093°W; Jul. 1996; 710 m; NMSZ.1999.237.4-5.

Diagnosis.

Prostomium fused with peristomium, giving the head a drop-like appearance; dorsal tentacles arising from segment 1 (achaetous), first pair of branchiae arising from segment 2 (achaetous); ventral groove; long capillary chaetae on expanded anterior, numerous long, broad flat spines on high complete cinctures (Fig. 14 ). No particular methylene blue staining pattern.

Molecular diagnosis.

Chaetozone sp. 2: COI: 130: G; 173: A; 202: T; 244: C; 293: C; 295: T; 309: G; 310: C; 395: G; 434: G; 454: T; 460: G; 470: G; 471: T; 477: C; 490: C; 302-303: AC; 564-565: CG. 28S: 408: A; 415: C; 416: A; 445: A; 571: C; 454-455: AG; 460-461: TC; 691-692: AA; 704-705: TC. (based on 8 COI sequences and 4 28S sequences) Chaetozone sp. 4: COI: 122: T; 487: G; 574: G (based on 10 COI sequences).

Remarks.

These considerably distinct molecular lineages but morphologically identical species, Chaetozone sp. 2 and Chaetozone sp. 4, are morphologically similar to C. monteverdii sp. nov. It is clear from the molecular analyses that they are different species from C. monteverdii sp. nov. Moreover, they are distinguished from C. monteverdii sp. nov. by having smooth long chaetae instead of segmented long chaetae, and a ventral groove instead of a ridge. Nevertheless, while none of the specimens of these two species examined present enlarged first segments, the condition present in Chaetozone spp. 2 and 4 could fit within the intra-specific variation documented in C. monteverdii sp. nov. The prostomium and peristomium in Chaetozone sp. 4 may also appear more distinctly separated than in the other species (Fig. 9 ). Chaetozone spp. 2 and 4 resemble C. jubata . However, they differ in the relative position of the paired tentacles and first pair of branchiae. It will be necessary to examine more specimens of each species, including of C. jubata , to investigate the intra-specific diversity in each group before confirming that neither Chaetozone sp. 2 nor Chaetozone sp. 4 are C. jubata .

The COI distance between Chaetozone sp. 2 and Chaetozone sp. 4 is 26% (Table 2 ). COI distances with other species in the area generally varies between 22% and 27%, with minimum at 9% between Chaetozone sp. 4 and Chaetozone quinta sp. nov. (Table 2 ).

Distribution.

Norwegian coast and shelf, offshore and in the fjords, where they occupy a wide range of depths from ~ 200 m to 1200 m depth.

Figures

Figure 9. Chaetozone monteverdii sp. nov., Holotype ZMBN 98250 in lateral view.

Figure 14. Chaetozone sp. 4. A ZMBN 125798, SEM of anterior end in dorsal view B ZMBN 125776, SEM of posterior spines C ZMBN 125798, SEM of peristomium epidermis D ZMBN 125798, SEM of ciliated organ E ZMBN 125776, SEM of neuropodial spine. Abbreviations: br, branchiae; Ch, chaetiger; cO, ciliated organ; dT, dorsal tentacles; nuO, nuchal organ; per, peristomium; pr, prostomium; Seg, segment.