Thelepus megalabiatum Carrerette, Nogueira & Hutchings, 2017, n. sp.
Creators: name: Carrerette, Orlemir
name: Nogueira, João Miguel De Matos
name: Hutchings, Pat
Publisher: name: Zenodo
Year: 2017
Subjects: Biodiversity
Taxonomy
Animalia
Annelida
Polychaeta
Terebellida
Terebellidae
Thelepus
Thelepus megalabiatum

description: Thelepus megalabiatum n. sp.
(Figs 3–4, Table 1)
Thelepus cf. setosus. (Non Quatrefages) Alves 2008: p. 81–87, figs 26–27.
Type series. Atlantic Ocean, southeastern Brazil, state of Rio de Janeiro, Campos Basin, project ‘HABITATS – Environmental heterogeneity in the Campos Basin’: Holotype (MZUSP 3017): 21°27'56.300"S 40°56'28.755"W, 15 m deep, in sand, coll. 20 Jul. 2009; paratypes 1–4 (MZUSP 3018, 3019, 3043, 3044, respectively): 22°45'44.583"S 41°45'39.316"W, 48.2 m deep, in sand, coll. 16 Jul. 2009.
Additional material examined. Project 'BIOTA/FAPESP/Benthic marine biodiversity in the state of São Paulo’: 23°25’S 44°46’W, 35 m deep, in sand, coll. 10 Jun 2001, 1 spec. Data on the range of variation of numerical characters within the type series is provided in Table 1.
Description. All specimens incomplete, with 51–78 (78) segments, 40–113 (60) mm long, 4–7 mm (7) wide. Preserved body uniformly beige to yellowish, without distinct patterns of pigmentation (Fig. 3 A–I). Transverse prostomium attached to dorsal surface of upper lip; basal part with two well separated irregular rows of eyespots, both continuous throughout, eyespots more separated from each other mid-dorsally (Fig. 3 D–H); distal part of prostomium low, restricted to base of upper lip (Fig. 3 C, F, H), thick and deeply grooved buccal tentacles, reaching around segment 10 if directed posteriorly (missing in holotype). Peristomium restricted to lips, not continuing dorsally; upper lip short and thick, hood-like, much wider than long (Fig. 3 A–H); large lower lip, swollen, as trapezoidal, distally rounded lobe extending posteriorly until segment 3 (Fig. 3 A, F–H). Anterior body highly glandular ventrally, corrugated and crenulate until segments 26–35 (31), progressively less marked and shorter from segments 16–17 (Fig. 3 A, D, F–H); segment 1 narrow all around, covered by lower lip mid-ventrally (Fig. 3 A, C, F–H); segments 2–7 progressively longer, with thickened, raised anterior margins laterally and ventrally, forming continuous crests across ventrum (Fig. 3 A, D–H); following anterior segments about same size. Three pairs of branchiae, on segments 2–4, segment 2 with 27–42 (35) branchial filaments on each side, segment 3 with 22–26 (25) filaments, segment 4 with 17–22 (18) filaments; origin of filaments of segment 2 extending slightly laterally to the level of notopodia, those of following segments originating dorsally to notopodia;
filaments of either side within pairs separated by wide, progressively larger mid-dorsal gap; branchial filaments long and thin, reaching in length about half of body width at corresponding segment, originating from swollen, apparently glandular areas (Fig. 3 B–E, G–H). Notopodia from segment 3 until the segments 44–61+ (44), progressively longer and inserted more laterally on segments 3–4; notopodia progressively shorter from mid-body, last pairs well developed (Fig. 3 B–I); narrowly-winged notochaetae in both rows, well marked difference in length between rows on anterior notopodia, less marked posteriorly, wings only present on distal halves of chaetae, slender, lanceolate, slightly wider basally (Fig. 4 A–C). Neuropodia as fleshy ridges on anterior body, progressively wider until termination of mid-ventral glandular areas, accompanying narrowing of glandular areas; after termination of glandular areas, neuropodia progressively narrower and more raised, and as narrow pinnules after notopodia terminate (Fig. 3 A–B, D–I), internal support rods only present after notopodia terminate; uncini with terminal dorsal button, remarkably short prow, as almost inconspicuous triangular knob, crest with 2 rows of secondary teeth, basal row with 2 large teeth, distal row with single tiny tooth in between teeth of first row, and base strongly convex (Fig. 4 D–G). Small nephridial and genital papillae on segments 4–7, posterior to bases of notopodia and between parapodial lobes. Pygidium unknown.
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Remarks. Members of T. megalabiatum n. sp. have been identified by previous authors as T. setosus or T. cf. setosus (Alves 2008, Amaral et al. 2013), but they differ from the holotype of T. setosus, after the redescription above, in the morphology of branchiae and uncini, as well as in the shape of anterior segments and position of neuropodial tori. The holotype of T. setosus has fewer branchial filaments (Table 2) and they originate directly from the body wall, leaving very narrow gap between filaments of either side of pairs, while members of T. megalabiatum n. sp. have more branchial filaments, originating from swollen cushions, with wide mid-dorsal gap between filaments within pairs (compare our Figs 1 B–C, E–G and 3B–E, G–H). The uncini are very similar between members of these species, but the holotype of T. setosus has a characteristic medial indentation at base, which is not found among members of T. megalabiatum n. sp. In addition, while the Brazilian species present high ventral crests on anterior segments and neuropodia varying in width, according to the width of the mid-ventral glandular areas, the holotype of T. setosus has much lower crests on anterior segments and neuropodia of uniform width.
As discussed above, specimens from several other localities around the world were first identified as T. setosus and then assigned to other species, in most cases new ones. These species are T. haitiensis Treadwell, 1931, T. verrilli (Treadwell, 1911) and T. fraggleorum Capa & Hutchings, 2006, from the Caribbean, and T. extensus Hutchings & Glasby, 1987, from Australia. Among these, T. fraggleorum, T. verrilli and T. extensus differ from the new species in regards to the numbers of both branchial filaments and pairs of notopodia (see Table 2). Thelepus haitiensis shares with T. megalabiatum n. sp. similar number of branchial filaments and rows of secondary teeth of uncini, but members of T. haitiensis do not have eyespots and present only up to 46 pairs of notopodia (Table 2), while members of the Brazilian species have two well developed rows of eyespots and notopodia extending until segments 44–61+. In addition, members of T. megalabiatum n. sp. have high ventral crests on segments 2–7, which are absent in T. haitiensis (compare Fig. 3 A–B, D–E, G–H with Londoño-Mesa 2009, fig. 24A–E, p. 81).
Finally, T. megalabiatum n. sp., differs from the other species described herein in the size of the specimens, the characteristic remarkably large lower lip, numbers of both branchial filaments and pairs of notopodia, as well as in the shape of ventral glandular areas and morphology of the uncini (see below).
Etymology. We attribute the epithet “ megalabiatum ” to this taxon in reference to the large size of lower lip, projecting as a ventral lobe reaching segment 3.
Type locality. Atlantic Ocean, Southeastern Brazil, state of Rio de Janeiro, Campos Basin: 21°27'56.300"S 40°56'28.755"W, 15 m deep, in sand.
description: Published as part of Carrerette, Orlemir, Nogueira, João Miguel De Matos & Hutchings, Pat, 2017, The genus Thelepus Leuckart, 1849 (Annelida, Thelepodidae) in Brazil, with a redescription of the holotype of T. setosus (Quatrefages, 1866), pp. 587-599 in Zootaxa 4250 (6) on pages 591-595, DOI: 10.11646/zootaxa.4250.6.6, http://zenodo.org/record/495872