Terebellides bakkeni, Parapar & Capa & Nygren & Moreira, 2020

Parapar, Julio, Capa, Maria, Nygren, Arne & Moreira, Juan, 2020, To name but a few: descriptions of five new species of Terebellides (Annelida, Trichobranchidae) from the North East Atlantic, ZooKeys 992, pp. 1-58 : 1

publication ID	https://dx.doi.org/10.3897/zookeys.992.55977
publication LSID	lsid:zoobank.org:pub:0F038B5B-120E-4583-8E85-4092C9798566
persistent identifier	https://treatment.plazi.org/id/0D530A3C-65B2-4F9D-A78A-051AE5B62110
taxon LSID	lsid:zoobank.org:act:0D530A3C-65B2-4F9D-A78A-051AE5B62110
treatment provided by	ZooKeys by Pensoft
scientific name	Terebellides bakkeni
status	sp. nov.

Treatment

Terebellides bakkeni sp. nov. Figs 1 View Figure 1 , 2 View Figure 2 , 3A View Figure 3 , 4A View Figure 4 , 5 View Figure 5 , 6 View Figure 6 , 8A View Figure 8 , 9 View Figure 9 , 17A View Figure 17 ; Table 1; Suppl. material 1: Table S1; Suppl. material 2: Table S2

Species 10 Nygren et al. 2018: 18-22, figs 6, 10.

Material examined.

Type material. Holotype: ZMBN116395. Paratypes (10 specimens): Barents Sea (ZMBN116388, ZMBN116389), Norwegian coast and shelf (ZMBN116390, ZMBN116391, ZMBN116392, ZMBN116393, ZMBN116394, ZMBN116396, NTNU-VM61376, NTNU-VM61377).

Holotype. Complete specimen, 32.0 mm long and 2.0 mm width (Figs 3A View Figure 3 , 4A View Figure 4 ).

GenBank accession numbers of material examined (COI).

Holotype: MG025165; Paratypes: MG025159, MG025160, MG025161, MG025162, MG025163, MG025164, MG025165, MG025166, MG025168, MG025169, MG025170. Additional material: MG025167.

Diagnostic features of type material.

Complete individuals ranging from 23.0-32.0 mm in length (Fig. 17A View Figure 17 ). Branchial dorsal lobes lamellae without papillary projections. Ventral branchial lobes generally hidden behind dorsal ones (Figs 3A View Figure 3 , 4A View Figure 4 , 5A-C View Figure 5 ). Lateral lappets and dorsal projection of thoracic chaetigers present on TC2(TC3)-TC5(TC4) (Fig. 5A View Figure 5 ). Geniculate chaetae in TC6 acutely bent, with low marked capitium (Fig. 6A, B View Figure 6 ). Ciliated papilla dorsal to thoracic notopodia (Fig. 5F View Figure 5 ). Thoracic uncini in one row with rostrum/capitium length ratio of approximately 2: 1 and capitium with a first row of three or four medium-sized teeth, followed by several smaller teeth (Fig. 6C-E View Figure 6 ). Abdomen with 25-29 pairs of neuropodia (Fig. 6F View Figure 6 ) with type 1 uncini (Fig. 6G View Figure 6 ).

Nucleotide diagnostic features.

Members of T. bakkeni sp. nov. share the following unique nucleotides at these given positions of our alignement: 162 (G), 168 (C), 345 (G; shared only with one specimen from species 17).

Type locality.

Nordland, Sortlaandssunder (Lofoten Islands); 119 m deep (Suppl. material 1: Table S1).

Distribution and bathymetry.

Barents Sea, Greenland Sea, northern Norwegian coasts from the Lofoten Islands to Trondheim; at depths of102-378 m ( Nygren et al. 2018) (Figs 8A View Figure 8 , 9 View Figure 9 ; Suppl. material 1: Table S1). One specimen found in North Iceland at 1,250 m deep.

Etymology.

This species is named after Dr. Torkild Bakken, from the NTNU-University Museum, Trondheim (Norway), housing institution of some of the specimens used in the present study, for his dedication to the study of Norwegian polychaetes and his friendship.

Remarks.

Terebellides bakkeni sp. nov. is a small-sized species, maximum-sized specimens reaching 20.0 mm in length (n = 3). This species is characterised by the presence of ciliated papilla dorsal to thoracic notopodia, lack of papillae on the margins of branchial lamellae and presenting abdominal uncini of type 1. Most of these features are also shared by the closest relative, T. stroemii (species 11 herein), but they differ in the morphology of the abdominal uncini, being of type 2 in T. stroemii and type 1 in T. bakkeni sp. nov. (Table 1 View Table 1 ). One specimen studied with SEM showed ciliary tufts in the inner side of the branchial lamellae (Fig. 5D View Figure 5 ). If this feature is not an artefact and is confirmed in all members of the species - so far only two specimens were examined under SEM - it would be an autapomorphy for the species. A similar feature was found in the non-closely related T. gracilis , that is also present in NEA. The ciliary tufts in T. bakkeni sp. nov. are, however, connected by rows of cilia (Fig. 5D View Figure 5 ), while in T. gracilis they are confined to isolated tufts ( Parapar et al. 2011: 12, fig. 9c). On the other hand, there are no clear morphological differences between T. bakkeni sp. nov. and T. kongsrudi sp. nov. (species 13). These sympatric species differ in the southern limit of their geographic distribution: T. bakkeni sp. nov., as T. kongsrudi sp. nov. are present above 65°N (Fig. 8A, C View Figure 8 ) while the latter and T. stroemii reach more southern latitudes, such as the Skagerrak and Bergen respectively (Fig. 8B, C View Figure 8 ).

Of the 462 sequences, including all NEA species, and 659 positions in the COI alignment, the 12 sequences assigned to T. bakkeni sp. nov. hold two unique nucleotides positions, and an additional one only shared by a single specimen from another clade (see Suppl. material 2: Table S2). The species also showed 0-1.9% of intraspecific divergence in the COI marker, and a minimum of 11.5% uncorrected genetic distance with congeners (in this case T. stroemii ) ( Nygren et al. 2018).