Thelepus setosus Quatrefages 1866
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 setosus

description: Thelepus setosus (Quatrefages, 1866)
(Figs 1–2)
Phenacia setosa Quatrefages 1866: 376 –377. Thelepus setosus Hilbig 2000: 231 –294.
Material examined. Holotype (MNHN type 464): Atlantic Ocean, northern coast of France, Normandie, Saint Vaast; slides: uncini segs 9, 19, 33 and 75; notochaetae segs 51 and 53.
Description. Holotype in excellent state of preservation, complete, with ~93 segments, ~ 110 mm long, 3.9 mm wide at widest point (segment 19); body progressively wider until segment 19, then of uniform width through
1. not Pseudothelepus nyanganus Augener, 1918, which is a species of Streblosoma.
segment 22, strongly tapering on segments 23–29, then uniformly cylindrical (~ 1 mm wide) through posterior body, slightly tapering near pygidium (Fig. 1 A–B). Transverse prostomium attached to dorsal surface of upper lip; basal part of prostomium without eyespots (perhaps eyespots originally present, but faded out in holotype now); distal part of prostomium shelf-like, several buccal tentacles present (Fig. 1 A–H), longest tentacles accidentally removed due to manipulation, but originally reaching ~segment 14 if directed posteriorly. Peristomium restricted to lips, not continuing dorsally; upper lip wider than long, with almost straight margins; rectangular lower lip, surrounded by mid-ventral lobe originated from segment 1, holotype with pharyngeal organ everted (Fig. 1 A, C– D, F–H). Anterior body highly glandular ventrally, crenulate to slightly corrugated between neuropodia until segment 9 (Fig. 1 A, C–D, F–H); segment 1 with dorsal crest originating from anterior margin and ventral lobe around lower lip; segments 2–7 progressively longer, segment 3 distinctly shorter ventrally than segments 2 and 4 (possibly another artefact, due to muscular contraction at time of preservation), then segments progressively increasing in length very slightly until segment 19; progressively less marked ventral crests on anterior margins of segments 2–7 (Fig. 1 A–H). Three pairs of branchiae, on segments 2–4, at most 20 filaments (considering scars) on segment 2, 10–15 on segment 3 and less than 10 on segment 4; origin of filaments of segment 2 extending slightly laterally to level of notopodia, those of following segments originating dorsally to level of notopodia; filaments of either side within pairs separated by distinctly narrow mid-dorsal gap, almost inconspicuous on segment 2; filaments originating directly from body wall, no cushion-like areas present (but body wall slightly swollen at point of insertion); filaments gently curled, reaching in length at most half of body width at corresponding segment (Fig. 1 B–C, E–G). Notopodia present on segments 3–56; notopodia of segments 3–8 inserted very slightly progressively more laterally, then longitudinally aligned (Fig. 1 B–C, E–G); notopodia progressively shorter from mid-body, last pairs almost inconspicuous; most chaetae shaved off, entire chaetae only present on posterior notopodia; narrowly-winged notochaetae in both rows, well marked difference in length between rows, wings only present on distal halves of chaetae, broader at base, lanceolated (Fig. 2 A–B). Neuropodia as fleshy ridges on anterior body, progressively narrower and more raised from mid-body segments, as narrow pinnules after termination of notopodia (Fig. 1 C, F–G, I), internal support rods only present after notopodia terminate; uncini with terminal dorsal button, remarkably short prow, as protruding triangular knob, crest with 2 rows of secondary teeth, basal row with 2 large teeth, distal row with single minute tooth in between teeth of first row, and strongly convex base, with medial indentation (Fig. 2 C–G). Distinctly small nephridial and genital papillae, posterior to bases of notopodia and between parapodial lobes of segments 4–7 (Fig. 1 E–G). Pygidium smooth (Fig. 1 A, I).
Remarks. The study of the holotype of T. setosus revealed an important mistake in the original description. According to Quatrefages (1866) the holotype has 45–46 thoracic segments and 34–35 abdominal ones, while it in fact has ~93 segments, with notopodia present until the segment 56 (= “thorax”), but thorax and abdomen are not well defined in this species, as the uniformly cilindrical region begins well before the termination of notopodia (see Nogueira et al. 2010, 2013), meaning there are ~37 abdominal segments, the last ones in formation, very compacted and difficult to count. Besides the number of thoracic and abdominal segments, the original description only provides some unclear information about the insertion of the branchial filaments (Quatrefages 1866).
Finally, the description above says eyespots are absent, but this may be an artefact due to the holotype being in ethanol for more than 150 years. Perhaps eyespots were originally present, but they are completely faded now, only remaining a thin darker line at base of basal part of prostomium (Fig. 1 G).
Type locality. Atlantic Ocean, France, Normandy, St. Vaast.
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 588-590, DOI: 10.11646/zootaxa.4250.6.6, http://zenodo.org/record/495872