Terebellides Group B (sensu Nygren et al. 2018)

Barroso, Maria, Moreira, Juan, Capa, Maria, Nygren, Arne & Parapar, Julio, 2022, A further step towards the characterisation of Terebellides (Annelida, Trichobranchidae) diversity in the Northeast Atlantic, with the description of a new species, ZooKeys 1132, pp. 85-126 : 85

publication ID	https://dx.doi.org/10.3897/zookeys.1132.91244
publication LSID	lsid:zoobank.org:pub:4168C32E-37A7-4912-A909-4912E69030AA
persistent identifier	https://treatment.plazi.org/id/612825B9-1C42-512D-AD48-8660C27B8944
treatment provided by	ZooKeys by Pensoft
scientific name	Terebellides Group B (sensu Nygren et al. 2018)
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Figs 2 View Figure 2 , 3 View Figure 3 , 4 View Figure 4 , 5 View Figure 5 , 6 View Figure 6 , 7 View Figure 7 , 8 View Figure 8 , 9 View Figure 9 , 10 View Figure 10 , 11 View Figure 11 , 12 View Figure 12

Description.

The morphological features shared by all examined species in Group B in this paper (clades 1, 5, and 16) are itemised below. Some of these are also shared by Groups A, C, and D as defined in Nygren et al. (2018) (see Remarks below). Clades 4, 14, and 26 will be studied elsewhere; formal descriptions of clades 17 and 27 will wait until more material is available.

Body appearance. Complete individuals ranging from 5.0-35.0 mm in length. Body tapering posteriorly with segments increasingly shorter and crowded towards pygidium. Prostomium compact; large tentacular membrane surrounding mouth (Figs 2B View Figure 2 , 3B, C View Figure 3 ), with typical buccal tentacles with expanded tips (Figs 2A, B View Figure 2 , 3A, B View Figure 3 ). SG 1 as an expanded structure below tentacular membrane in a lower lip.

Branchiae. Branchiae arising as single structure from SG 3, with a single stalked mid-dorsal stem (Figs 2A, B View Figure 2 , 3B, C View Figure 3 , 4B View Figure 4 ), lobes not fused or partially fused, ventral ones obscured or not by dorsal ones (Figs 2A, B View Figure 2 , 3A-C View Figure 3 , 4A, B View Figure 4 ). Dorsal lobes ending posteriorly in short terminal papilla and ventral lobes ending in long filaments (Figs 2B View Figure 2 , 3A, B View Figure 3 ). Anterior projection of dorsal lobes (fifth lobe) normally absent but present only in clade 5 (Fig. 3B View Figure 3 ). Posterior end of dorsal lobes reaching TC 4 (Figs 2A, B View Figure 2 , 3A, B View Figure 3 ). Branchial lamellae provided with several parallel rows of cilia in inner face (Fig. 6C View Figure 6 ) and ciliary tufts not observed. Ciliary papillae absent in branchial lamellae margin.

Thorax. Eighteen pairs of notopodia (SG 3-20), those of TC 1 ca. as long as subsequent ones or slightly shorter (Figs 2A View Figure 2 , 3A-C View Figure 3 ). Lateral lappets and dorsal projections of notopodia in anterior thoracic chaetigers with different degree of development depending on size and preservation conditions, but both more conspicuous on TC 1-4 (Fig. 3A-C View Figure 3 ). All notochaetae as simple capillaries (Fig. 5B View Figure 5 ). Size of notochaetae of TC 1 similar to subsequent ones. Neuropodia as sessile pinnules from TC 6 to body end, with uncini in single or double rows, from TC 7 throughout. Neuropodia on TC 6, provided with several sharply bent, acute-tipped, geniculate chaetae with minute teeth forming a capitium only visible with SEM (Figs 5C View Figure 5 , 7A View Figure 7 , 8C View Figure 8 ). From TC 7, neuropodia with one or several rows of uncini per torus (Figs 5D View Figure 5 , 7B, C View Figure 7 , 8D View Figure 8 ), with long shafted denticulate hooks, with large main fang (rostrum) longer than upper crest of teeth (capitium), rostrum/capitium length ratio of ~ 2:1, capitium composed by several teeth above main fang of decreasing length (Figs 5D View Figure 5 , 7B View Figure 7 , 8D View Figure 8 ).

Abdomen and pygidium. Approximately half as long as thorax and progressively thinner (Fig. 2A-C View Figure 2 ). Neuropodia ranging from 18-34 chaetigers and forming erect pinnules (Figs 5E View Figure 5 , 8E View Figure 8 ) with several uncini per torus, number depending on specimen size. Uncini provided with several teeth above rostrum surmounted by a capitium composed of several teeth of decreasing length (Figs 5F View Figure 5 , 7D View Figure 7 , 8F View Figure 8 ). Pygidium blunt, as funnel-like depression.

Colour pattern. Colour in preserved specimens whitish or pale brown (Fig. 3A-C View Figure 3 ). MG staining pattern characterised by 1) compact green colourant in SG 1-6, then turning into striped pattern in SG 7-14 and fading in following segments or 2) by compact green colourant in SG 1-6, J-shaped glandular region in SG 3-5, and striped pattern in SG 7-14 (Fig. 12 View Figure 12 ).

Remarks.

Among the aforementioned characters, branchial features might serve to distinguish most of Group B species from those of Groups A, C, and D. Those include size of branchial lobes, lobes not fused, presence of long filaments on ventral ones, and presence of ciliary rows on branchial lamellae. Other taxa described or reported worldwide bear the same type of branchiae (type 3), including Terebellides ehlersi McIntosh, 1885, T. intoshi Caullery, 1915, T. lobatus Hartman & Fauchald, 1971, T. mundora Hutchings & Peart, 2000 and T. sepultura Garraffoni & Lana, 2003 ( Parapar et al. 2016a, b).