Thelepus brevitori, 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 : 595-598

Thelepus brevitori n. sp.

( Figs 5–6 , Table 1 )

Thelepus setosus . (Non Quatrefages) Blankensteyn 1988: p. 74–77, fig. 18.

Type series. Atlantic Ocean, southeastern Brazil, state of São Paulo, project ‘ BIOTA /FAPESP/ Benthic marine biodiversity in the state of São Paulo’ : Holotype ( MZUSP 3020 ) and paratype 7 ( MZUSP 3045 ): 25°11.89'S 47°08.09'W, 50 m deep, in sand, coll. 16 Dec. 1997 ; paratypes 1–4 (MZUSP 3021, 3022, 3023, 3024, respectively): 23°42'541"S 45°11'380"W, 25.3 m deep, in sand, coll. 29 Jul. 2001; paratype 5 (MZUSP 3046): 23°25'663"S 44°46'570"W, 35 m deep, in sand, coll. 11 Jun. 2001; paratype 6 (MZUSP 3047): 23°45'062"S 45°13'856"W, 25.3 m deep, in sand, coll. 18 Oct. 2001. Data on the range of variation of numerical characters within the type series is provided in Table 1 .

Description. Preserved body uniformly beige to yellowish, without distinct patterns of pigmentation ( Fig. 5 A– G). All specimens incomplete, longest specimens with 68 (68) segments, 26 (25) mm long and 4 (3) mm wide. Transverse prostomium attached to dorsal surface of upper lip; basal part thick, with two thin irregular rows of eyespots continuous throughout, eyespots more separated from each other mid-dorsally ( Fig. 5 D–E, G); distal part of prostomium low, restricted to base of upper lip ( Fig. 5 D–E, G); buccal tentacles long and thin, reaching around segment 20 if directed posteriorly ( Fig. 5 A). Peristomium restricted to lips, upper lip short, thick, hood-like, wider than long; lower lip short, swollen, rectangular, wider than long, surrounded by mid-ventral lobe originated from segment 1 ( Fig. 5 C, F). Anterior body highly glandular ventrally, with thick, crenulated to slightly corrugated body wall between neuropodia, progressively narrower until segment 17 or slightly more posteriorly (17) ( Fig. 5 A, C– F); segment 1 with ventral lobe around lower lip, marginal to mouth; segments 2–4 shorter, then segments increasing progressively in length very slightly until mid-body ( Fig. 5 A–F). Three pairs of branchiae, on segments 2–4, segment 2 with 10–18 (15) branchial filaments, segment 3 with 5–10 (10) filaments, segment 4 with 4–8 (8) filaments, leaving wide mid-dorsal gap; origin of filaments of segment 2 dorsal to level of notopodia, not extending laterally; branchial filaments originating directly from body wall, cushion-like areas absent ( Fig. 5 G). Notopodia present until segments 26–29, 29 in most specimens, including holotype; relatively short and bilobed notopodia, lobes of equal size, notopodia progressively longer and more laterally placed on segments 3–6, then longitudinally aligned laterally ( Fig. 5 A–B, D–E, G). Narrowly-winged notochaetae in both rows, poorly marked difference in length between rows, shafts expanded at bases of wings, rounded, especially in anterior row ( Fig. 6 A–C). Neuropodia as low, fleshy ridges on anterior segments, narrow tori of uniform width, laterally aligned ( Fig. 5 A, D– E), as raised cushion-like pinnules after notopodia terminate ( Fig. 5 A–B); uncini with terminal dorsal button, remarkably short prow, as protruding knob, base relatively large and convex, and crest with 2 rows of secondary teeth, each with 2 teeth, medial indentation absent ( Fig. 6 D–H). Nephridial and genital papillae not visible. Pygidium unknown.

Remarks. Members of T. brevitori n. sp. differ from both species described above, T. setosus and T. megalabiatum , in the morphology of branchiae, with few and relatively short and thick filaments, leaving a wide mid-dorsal gap, and in only having up to 27 pairs of notopodia, extending until segment 29. In contrast, in members of both other species the branchiae have more filaments and these are longer and thinner, originating from cushionlike areas in T. megalabiatum , and notopodia extending until segment 56 in the holotype of T. setosus , and segment 44–61+ in the case of members of T. megalabiatum ( Table 2 ). In addition, Thelepus brevitori n. sp., is a much smaller species, as the holotype of T. setosus has ~93 segments and it is ~ 110 mm long and 3.9 mm wide, and that of T. megalabiatum has 78 segments and it is 113 mm long and 7 mm wide ( Table 2 ).

In regards to the other species previously identified as T. setosus , i.e., T. haitiensis and T. fraggleorum , from the Caribbean, and T. extensus , from Australia, members of T. brevitori n. sp. also differ mostly in numbers of both branchial filaments and pairs of notopodia. Specimens of T. haitiensis have many more filaments, arising from cushion-like bases, and 41–46 pairs of notopodia, and members of T. fraggleorum have similar number of branchial filaments to that observed in T. brevitori n. sp. (see Table 2 ), but they have notopodia extending up to segment 72. Members of T. extensus also have many more branchial filaments and notopodia extend until segment 37 ( Table 2 ).

Two other species share with T. brevitori n. sp. the presence of ~30 pairs of notopodia. These species are T. pascua ( Fauchald, 1977) , from Panama, and T. crassibranchiatus Treadwell, 1901 , from Puerto Rico. However, both these species have only two pairs of branchiae, instead of three pairs as in members of T. brevitori n. sp., and these branchiae have only 4 filaments in the first pair and 2 in the second pair in members of T. crassibranchiatus , and a single and long filament on each side, in both pairs, in T. pascua ( Table 2 ).

Finally, the notochaetae from the anterior row of T. brevitori n. sp., are unique, not found in any of the other species in this genus, with expanded and laterally rounded shaft at the base of the wing, and narrow wing of uniform width.

Etymology. We attribute the epithet “ brevitori ” to this taxon in reference to the narrow width of the neuropodial tori along the body.

Type locality. Atlantic Ocean , Southeastern Brazil, state of Rio de Janeiro: 25°11.89'‟ S 47°08.09' ‟W, 50 m deep, in sand.

Figures

FIGURE 5. Thelepus brevitori n. sp. (Holotype, MZUSP 3020), (A). Incomplete worm, left lateral view; (B – E). Anterior body, dorsal, ventral, left and right lateral views, respectively; (F – G). Close ups of the anterior end, ventral and dorsal views, respectively. Numbers refer to the segments; e = eyespots; g = glandular ventral areas; ll = lower lip; l 1 = lobe on segment 1; no = notopodia; n = neuropodium; P = basal part of prostomium; po = pharyngeal organ; ul = upper lip; * distal part of prostomium. Scale bars: A = 0.5 mm; B – G = 0.3 mm.

FIGURE 6. Thelepus brevitori n. sp. (Holotype, MZUSP 3020), (A – C). Notochaetae, segments 8 and 26 (2), respectively. (D – G), uncini, segments 5, 18, 33 (2), and 26, respectively. b = base of uncinus; c = crest with secondary rows of teeth; db = dorsal button; h = heel; mf = main fang; p = prow. Scale bars: A – C = 60 µm; D – F = 30 µm; F = 10 µm; G – H = 20 µm.