Thelepus megalabiatum, Carrerette, Orlemir, Nogueira, João Miguel De Matos & Hutchings, Pat, 2017

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), Zootaxa 4250 (6), pp. 587-599: 591-595

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Thelepus megalabiatum

n. sp.

Thelepus megalabiatum  n. sp.

( Figs 3–4View FIGURE 3View FIGURE 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 3017View Materials): 21°27'56.300"S 40°56'28.755"W, 15 m deep, in sand, coll. 20 Jul. 2009GoogleMaps  ; 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. 3View FIGURE 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. 3View FIGURE 3 D –H); distal part of prostomium low, restricted to base of upper lip ( Fig. 3View FIGURE 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. 3View FIGURE 3 A –H); large lower lip, swollen, as trapezoidal, distally rounded lobe extending posteriorly until segment 3 ( Fig. 3View FIGURE 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. 3View FIGURE 3 A, D, F –H); segment 1 narrow all around, covered by lower lip mid-ventrally ( Fig. 3View FIGURE 3 A, C, F –H); segments 2–7 progressively longer, with thickened, raised anterior margins laterally and ventrally, forming continuous crests across ventrum ( Fig. 3View FIGURE 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. 3View FIGURE 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. 3View FIGURE 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. 4View FIGURE 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. 3View FIGURE 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. 4View FIGURE 4 D –G). Small nephridial and genital papillae on segments 4–7, posterior to bases of notopodia and between parapodial lobes. Pygidium unknown.


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 1View FIGURE 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. 3View FIGURE 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.GoogleMaps 

TABLE 1. Morphological variation within the type-series of Thelepus megalabiatum n. sp. and Thelepus brevitori n. sp.

    Number of segments (all specimens of both species incomplete)      
T. megalabiatum  n. sp. Holotype          

TABLE 2. Comparison between the most important numerical characters of the species of Thelepus most similar to T. megalabiatum n. sp. and T. brevitori n. sp. Sources: Hutchings & Glasby (1987); Londoño-Mesa (2009); Capa & Hutchings (2006); characters of T. setosus examined directly from type-material.

          teeth row st of 1 Number secondary uncini row of nd 2  
            Atlantic Ocean, Southeastern Brazil, state of Rio de Janeiro
T. extensus Hutchings  & Glasby, 1987            

Museu de Zoologia da Universidade de Sao Paulo