Terebellides sp. 2

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

Terebellides sp. 2 Figs 1 , 2 , 9 , 27 ; Table 1; Suppl. material 1: Table S1; Suppl. material 2: Table S2

Species 21 Nygren et al. 2018: 18-22, figs 5, 6, 10.

Material examined.

4 specimens: Barents Sea. ZMBN 116481; ZMBN 116486.

Remarks.

As explained for Terebellides sp. 1, two specimens were examined under SEM; these share with T. bigeniculatus the irregular shape of branchial lobes (Fig. 27A ), the presence of geniculate chaetae on TC5 and TC6 (Fig. 27C-E ) and abdominal uncini of type 1B (Fig. 27G ). They share with subgroup A1 the presence of one ciliated papilla dorsal to thoracic notopodium (Fig. 27B ) and thoracic uncini of type 3 (Fig. 27F ).

On the other hand, species 18 and 19 of A1 (not described here because of the few specimens being available) and 23 (A4) have a geographic distribution similar to that of T. bigeniculatus but their position in the cladogram by Nygren et al. (2018: fig. 5) suggests that they may not bear geniculate chaetae in two chaetigers.

There are no unique diagnostic nucleotide positions that are shared by the two haplotypes (in 18 sequences) in COI. Eighteen sequences, in one single haplotype, have been attributed to this species ( Nygren et al. 2018). Members of this species show a minimum of 3.0% uncorrected genetic distance, with its closest relative being T. bigeniculatus (Fig. 1 ).

Figures

Figure 1. Phylogenetic tree after Maximum Likelihood analyses on a concatenated dataset of cox 1, 16 S rDNA, ITS 2, and 28 S rDNA (as in Nygren et al. 2018). Bootstrap support values above nodes. Coloured squares indicate the major clades referred herein as Groups A-D. Within Group A, the focus of present study, subgroups A 1 - A 4 and species 6 - 13, 18 - 21, 23, 28 are labelled.

Figure 2. Phylogenetic tree after Maximum Likelihood analyses on a dataset of cox 1 (including all sequences in Nygren et al. 2018 and in Lavesque et al. 2019). Bootstrap support values above nodes. Species other than members of Group A are collapsed. Species with names refer to those dealt with in present study.

Figure 9. Bathymetric distribution of Terebellides species studied in this work. Subgroups (A 1 - 3) within group A sensu Nygren et al. (2018) are indicated.

Figure 27. Terebellides sp. 2 (species 21; ZMBN 116481 and ZMBN 116486), SEM micrographs. A anterior end, left lateral view B TC 10, thoracic dorsal papilla (framed in A) C, D geniculate chaetae of TC 5 and TC 6 respectively (framed in A) E TC 6, geniculate chaeta (arrow pointing to capitium teeth) F thoracic uncinus G abdominal uncini. Abbreviations: TC - thoracic chaetiger; tdp - thoracic dorsal papilla.